CN1438775A - Optical fiber, optical transmission path using same and optical communication system - Google Patents

Abstract

Optical fibers to form an optical transmission line suitable for WDM transmission in a wide-spreading wavelength band, having the following characteristics and parameters: a dispersion in absolute value of 0.5 ps/nm/km to 9 ps/nm/km in a wavelength band of 1430 nm to 1625 nm, a dispersion slope in absolute value of 0.04 ps/nm2/km or less at a wavelength of 1550 nm, a mode field diameter of 7 mum or less at a wavelength of 1550 nm and a cable cutoff wavelength of less than 1430 nm; core 11 surrounded by cladding 7, core 11 being at least two-layered (first layer 1 at the center and second layer 2 surrounding the first layer; relative refractive index of glass layer Delta 1 with reference to the cladding being adjusted to not less than 0.6 but not more than 1.6%, relative refractive index of second layer Delta 2 with reference to the cladding being adjusted to a negative value. Such can form light transmission passageway which is suitable for wavelengh subsection multiplex transmission of broader cellula.

Description

The optical transmission pathway and the optical communication system of optical fiber, this optical fiber of use

Technical field

The present invention relates to be suitable for the multiplex optical fiber of wavelength segmentation, the optical transmission pathway that uses this optical fiber and optical communication system.

Background technology

Because the development of information-intensive society, communication information amount has the tendency of increase at full speed, follows the increase of this amount of information, and wavelength segmentation multiplexing is widely used in the communications field.The transmission of wavelength segmentation multichannel is the mode of multi-wavelength's light with 1 Optical Fiber Transmission.

Now, as the light amplifier that is applicable to the multiplex relay station of wavelength segmentation, the light amplifier (EDFA) with the fiber that adds erbium has been used in exploitation.Owing to developed such optical-fiber type light amplifier, in above-mentioned relay station, each wavelength does not need converting optical signals is become the signal of telecommunication, has quickened the multiplex development of wavelength segmentation like this.

On the other hand, recently, receive publicity as new light amplifier with Raman's amplifier of Raman's amplification.Raman's amplification is to utilize the stimulated emission in the Raman scattering and the mode that makes light amplification, and the characteristic of nonlinear of this amplification efficient and optical fiber has much relations.In general, optical fiber non-linear big more, the efficient of Raman's amplification is high more.

Represented to utilize an example of the optical transmission system of Raman's amplification among Figure 23.In this figure, signal optical source 4a1～4an exports the flashlight of different wavelength respectively.Carry out multiplexing from the flashlight of each signal optical source 4a1～4an output with optical multiplexer 15.

Exciting light source 3a1～3an exports the exciting light of different wave length separately in addition.Usually, use the exciting light source of various ways vibration among exciting light source 3a1～3an.Multiplexing from the exciting light of each exciting light source 3a1～3an output with optical multiplexer 16.These exciting lights and above-mentioned flashlight (wavelength block signal light) are multiplexing with multiplexer 10, are imported in the optical fiber 8 that forms optical transmission pathway.

Be input to wavelength multistage flashlight in the optical fiber 8 by Raman's amplification, transmission in optical fiber 8 simultaneously, and the light demultiplexer 9 that is arranged on receiving optical signals one side is divided into each wavelength signals light, received by optical receiver 7a1～7an.

Optical transmission system shown in Figure 23 is an example of preceding excitation system, the place ahead (with the input one side identical direction of the flashlight) input of the exciting light that is used for Raman's amplification from optical fiber 8.As the other example of the optical transmission system of using Raman's amplifier, the back excitation is arranged as shown in figure 24, rear (direction of the flashlight output) input of the exciting light that is used for Raman's amplification from optical fiber 8.

Multiplexing from the exciting light of each exciting light source 13a1～13an output in this figure with optical multiplexer 26.Exciting light is with light demultiplexer 20 input optical fibres 8, to the direction transmission opposite with the flashlight transmission direction.

Other example with the optical transmission system of Raman's amplifier has two-way excitation as shown in figure 25, the exciting light that is used for Raman's amplification former and later two directions inputs from optical fiber 8.

In this figure, multiplexing from the exciting light of each exciting light source 3a1～3an output with optical multiplexer 16, multiplexing from the exciting light of each exciting light source 13a1～13an output with optical multiplexer 26.With optical multiplexer 10,20 these exciting lights are input in the optical fiber 8, respectively to forward and backward transmission.For the luminous intensity that makes optical fiber 8 length directions is more even, preferably use two-way excitation.

Under the situation that the quartzy based material of optical fiber 8 usefulness is made, the amplification peak value of the maximum of Raman's amplification is present in the frequency (about 100～110nm long wave, one side) than the low 13THz of the light frequency of exciting light, just makes the flashlight amplification of about 100～110nm long wave, one side from excitation wavelength with Raman's amplification.

Therefore for example in the optical transmission system of wavelength 1.5 mu m ranges, the flashlight of 1580nm amplifies in order to obtain maximum Raman, and must make exciting light is the 1480nm wavelength.In addition, in wavelength segmentation multiplex system, the exciting light with shortwave one side in the wave-length coverage of the flashlight of Wavelength branching makes the flashlight of shortwave one side carry out Raman's amplification, makes the flashlight of long wave one side carry out Raman's amplification with the exciting light of long wave one side.

In addition, optical fiber transmission property is relevant with frequency band (dispersion) characteristic with the loss of optical fiber.Spread fiber pattern with single-mode is single, owing to there is not pattern to disperse, transmission range is disperseed to determine by dispersion of materials and structure.With the single-mode optical fiber of existing form, near they disperse and vanishing wavelength 1.3m, light loss is then minimum in wavelength 1.5m scope in addition.Therefore, that proposed to make dispersion and be the scheme that zero wavelength (zero loose wavelength) is displaced to the 1.5 mu m range zeros astigmatism fibres (DSF:Dispersion-Shifted Fiber) of this wave-length coverage.Make the zero wavelength that looses be displaced to 1.5 mu m ranges,, change that value that structure disperses can make dispersion and skew because dispersion of materials is almost constant from 1.3 mu m ranges.Just, make zero loose wavelength shift to 1.5 mu m ranges by adjusting type sandwich layer cladding index curve.

Optical fiber transmission property in general wavelength dispersion is the smaller the better, and when making the incident of WDM flashlight in the optical fiber, if wavelength dispersion is little, fiber internal cause four light wave mixing phenomenas (FWM:Four-Wave Mixing) and produce useless ripple produce the problem that interchannel crosstalk increases.As the fiber of head it off, proposed to have the scheme of the non-zero dispersion deflection fiber (NZDSF:Non-Zero Dispersion Shifted Fiber) of suitable wavelength dispersion value.

One of research and development problem of current WDM transmission technology is to pursue to enlarge transmission range.Up to now, use wave-length coverage based on C-band (1530-1565nm) and L band (1565-1625nm), transmission also adapts to most this scope with optic fibre characteristic.The scheme of the reduction dispersion apsacline non-zero DSF (NZ-DSF) of consideration S-band (1460-1530nm) transmission has been proposed in recent years.(special hope 2001-100422, EOC 01 PD A1-5 (2001), OECC 02 11D1-2 (2002)).

, even reduce to disperse apsacline NZ-DSF, its transmission range also is subjected to the loose restriction of wavelength of zero in shortwave one side, is subjected to accumulating the restriction of dispersion relation in long wave one side.Consequently, the wave-length coverage that can transmit is restricted to about 200nm.In addition, under the situation of considering Raman's amplification, the zero of the NZ-DSF wavelength restriction Raman excitation range of loosing is particularly in Raman's amplification difficulty of S-band scope.

Therefore the objective of the invention is in the WDM transmission system, a kind of optical fiber that wideer transmission range can be arranged that can cover from E-band to the U-band wave-length coverage is provided.A kind of optical fiber of the distribution Raman amplification in the S-band scope is provided simultaneously.In addition, can realize to suppress nonlinear simultaneously, the optical cable that bending loses is little.

Summary of the invention

Shown in the characteristic curve a of Figure 26, loose wavelength at flashlight S in the zero of optical fiber _1～nWith exciting light R _1～mBetween under the situation about existing, flashlight S _1～nNeighbouring four light wave mixing F can take place _1～pFour light waves are mixed the light frequency f that takes place _FwmThe expression, flashlight S _1～nOr exciting light R _1～mLight frequency f _i, f _i, f _kDuring expression, f _Fwm=f _i+ f _i-f _kWherein, i ≠ k, i ≠ j.

The four light wave F that take place _1～pLuminous intensity and luminous efficiency η proportional, luminous efficiency η with (several 1) expression.Above-mentioned content is for example at MARI W.MAEDA, J.LightwaveTechnology, and vol.8, no.9, pp.1402, on the books in 1990.[several 1] $\mathrm{\η}=\frac{{\mathrm{\α}}^2}{{\mathrm{\α}}^2+{\mathrm{\Δ\β}}^2}[1+\frac{{4e}^{-\mathrm{aL}}{\sin }^2\left(\frac{\mathrm{\Δ\βL}}{2}\right)}{{(1-e^{-\mathrm{aL}})}^2}]$

Wherein, α is the loss of optical fiber, and L is the length of optical fiber.Δ β represents that the position that four light waves mix integrates condition mutually, is provided by (several 2).

[several 2] $\mathrm{\&Delta;\&beta;}={\mathrm{\&beta;}}_i+{\mathrm{\&beta;}}_j-{\mathrm{\&beta;}}_k-{\mathrm{\&beta;}}_{\mathrm{fwm}}$ $\&cong;\frac{{\mathrm{\&pi;\&lambda;}}^4}{{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="A0310441400562.png,A0310441400601.png"\; state="\{\{state\}\}">c</figure-callout>}}^2}\mathrm{Ds}\{(f_i-f_o)+(f_j-f_o)\}(f_i-f_k)(f_j-f_k)$

Wherein, β is a transmission, and c is the light velocity, and λ is a wavelength, and Ds is that optical fiber disperses to tilt f _i, f _i, f _k(but i ≠ k, i ≠ j) are flashlight S _1～nOr exciting light R _1～mLight frequency, f ₀Be the numerical value that the diffusing wavelength of the zero of optical fiber is converted into frequency.Take place phenomenon that four light waves mix flashlight and exciting light in optical fiber under the equidirectional transmission situation relatively significantly, (several 2) be approximately flashlight and exciting light approximate under the equidirectional transmission situation in optical fiber.

From (several 1) and (several 2) as can be seen, the zero of optical fiber is loose wavelength at flashlight S _1～nWith exciting light R _1～mBetween the time, because of flashlight S _1～nWith exciting light R _1～mAnd the four light wave mixing F that take place _1～pLuminous efficiency become big.

As mentioned above, if four light wave mixing F take place _1～p, flashlight S _1～nTransmission characteristic worsen, particularly big if four light wave mixings luminous efficiency η become, the luminous intensity of the exciting light that is seized by four light waves is also big, flashlight can not obtain big Raman's amplification.

The luminous efficiency that four light waves that take place because of flashlight and exciting light mix, particularly become big under the situation of equidirectional transmission in optical fiber at flashlight and exciting light, so can not encourage the problem that causes occurring to construct only optical transmission system by twocouese.

Therefore, in order to realize Raman's amplification wavelength segmentation multiplexing, it is one of important problem that four light waves that suppress to take place in the optical fiber mix.

Now, erbium fibrous type light amplifier is for example used in wavelength segmentation multiplexing, mainly is to serve as main carrying out from 1530nm to 1565nm with the wavelength that is called C-band.Scope from wavelength 1530nm to 1625nm is studied widely to the multiplex wave-length coverage of wavelength segmentation.The scope of wavelength from 1565nm to 1625nm is called L-band.

In order to construct Raman's transmission channel of 2 wave bands that used C-band and L-band, need when hanging down the 100nm left and right sides, import exciting light than the minimal wave length of transmission range.Consider and utilize the diffusing wavelength of the zero that makes optical fiber also lacking outside the following scope of the above 1625nm of 1430nm of 100nm, suppress four light waves and mix than 1350nm.

In addition, from 1460nm to 1530nm, more wish to realize wavelength segmentation multiplexing at the wavelength that is called S-band.For S, the C that realizes comprising S-band, 3 band transmission of L, wish to make the zero of optical fiber to loose wavelength outside the following scope of the above 1625nm of wavelength 1360nm.

In order to realize being applicable to the wavelength segmentation multiplex system of Raman's amplification, mix except suppressing above-mentioned four light waves, definite values such as the absorption loss water of determining to follow optical fiber to disperse inclination, actual effect core cross-sectional area, transmission loss, OH base, the dispersion of polarized wave form are necessary.

For example, owing to disperse to tilt big dispersion to cause wave distortion, actual effect core cross-sectional area can not obtain enough Raman's amplification efficient after increasing.Obstacle occurs if transmission loss greatly enhances Distance Transmission, it is big that the polarized wave form is disperseed, particularly during high-speed transfer (high-speed communication) because direction of polarized light causes the flashlight delay-time difference to become big, bring the problem of baneful influence with regard to there being transmission to flashlight.

Follow the absorption loss water of OH base, for example excitation wavelength contains under near the situation of the light of wavelength 1385nm, owing to can not obtain enough Raman's amplification efficient, the multiplex wide regionization of wavelength segmentation is impacted.

So, owing to do not have to satisfy the optical fiber of above-mentioned condition, the Raman's amplification wavelength segmentation multiplex system that can not construct high-quality, wide region in the existing scheme that proposes.

For example, owing to there is not the zero wavelength that looses in the general scope of single-mode optical fiber (SMF) below the above 1625nm of wavelength 1360nm, can avoid the problem of above-mentioned four light waves mixing., owing to the relevant n of single-mode optical fiber with the size of Raman's amplification ₂/ A _EffSmaller, can not obtain being enough to fully compensate Raman's amplification of the transmission channel extent of damage.n ₂Be coefficient, A _EffIt is actual effect core cross-sectional area.

For example, as shown in figure 27, it is equal that fiber loss and Raman are amplified, and must make n ₂/ A _Eff4.4 * 10 ^-10More than the W.So shown in the hatched example areas of figure, single-mode optical fiber can not satisfy this condition.

In addition, single-mode optical fiber has the big wavelength dispersion of pact+17ps/nm/km at wavelength 1.5 μ m frequency band ranges.Therefore the flashlight of wavelength 1.5 μ m frequency bands is subjected to the influence of big wavelength dispersion, owing to cause the intersymbol non-linear effect that pulse broadens and causes, is unsuitable for using single-mode optical fiber in the wavelength segmentation multiplexing of Raman's amplification.

For example, among Figure 28, the relation between the pulse that absolute value that expression optical fiber disperses and dispersion cause broadens.T is the inverse of bit rate, and t is four light wave hybrid frequencies of pulse.If T/T is below 0.4, intersymbol is overlapping little, is the intersymbol non-linear effect that can allow.

Therefore, in the system more than 10Gbps, the absolute value that the optical fiber of received signal light disperses must be below about 9ps/nm/km, and shown in figure bend zone, single-mode optical fiber is separated into about 17ps/nm/km, and t/T is above 0.4.Therefore be the optical fiber of single-mode unfavorable as optical transmission pathway.

In addition, also find to reduce the NZ-DSF that disperses apsacline even use under the situation that the flashlight in considering C-band and L-band transmits together, the difference of the dispersion value between the light signal wave band of use becomes the obstacle that enlarges passband range.Because the progress of the practicability of Raman's amplifier, also can consider as transmission channel NZ-DSF, S, C, L-band transmit together, in the optical fiber that EOC 01 PD A1-5 (2001), OECC 02 11D1-2 (2002) are disclosed, the Raman's excitation frequency band scope that is used for the flashlight of S-band is carried out Raman's amplification (comprises the zero wavelength that looses among the 1360nm～1430nm), mix so four light waves take place, have can not Raman's amplification restriction, seek to eliminate the optical fiber of these problems.

The present invention is in order to solve above-mentioned problem, its objective is that providing a kind of can suppress that four light waves mix, the absolute value that the absolute value of wavelength dispersion and dispersion are tilted is little, can effectively carry out Raman's amplification, it is little to wish that transmission loss, polarized wave form disperse, be applicable to the multiplex optical fiber of wavelength segmentation of Raman's amplification, with the optical transmission pathway and the optical transmission system of this optical fiber

To achieve these goals, the present invention is as the means that solve problem with following structure.

(1) make wavelength at the dispersion absolute value of 1430nm in the gamut of 1625nm below the above 9ps/nm/km of 0.5ps/nm/km, wavelength at the dispersion inclination absolute value of 1550nm at 0.04ps/nm ²Below/the km, the mode field diameter of wavelength 1550nm is that cable cut-off wavelength is less than 1430nm below the 7 μ m.

(2) in wavelength 1400～1700nm, dispersion value D is 2≤D≤8 (ps/nm/km), and has 1 extreme value at least at the wavelength of co-wavelength band region.

(3) making the dispersion value at wavelength 1550nm is more than the 4ps/nm/km, and the dispersion that at least a portion of wavelength 1460nm～1625nm is set in the wavelength band tilts to be 0.050ps/nm ²/ km following on the occasion of, the cut-off wavelength that makes length 2m makes zero loose wavelength below 1460nm below 1550nm, the transmission loss of wavelength 1385nm is below 1.5dB/km.

Description of drawings

Fig. 1 (a) and (b) be the refractive index curve structure (a) of embodiment 1 of expression optical fiber of the present invention and the key diagram of profile of optic fibre structure (b).

(a) of Fig. 2 and (b) be the loose key diagram that concerns example of wavelength and exciting light and signal light wavelength of the optical fiber zero of expression embodiments of the invention 1 (a) is positioned at the example that concerns of the wavelength of lacking than 1360nm for the diffusing wavelength of zero; (b) be positioned at the example that concerns of the wavelength shorter for the zero wavelength that looses than 1430nm.

Fig. 3 is the diffusing wavelength of zero of the optical fiber of the expression embodiment of the invention 1 and the key diagram that concerns example of exciting light and signal light wavelength, and the diffusing wavelength of zero is positioned at the example that concerns of the wavelength longer than 1625nm.

Fig. 4 represents the curve of the fiber optic wavelength dispersing characteristic example of the embodiment of the invention 1.

Fig. 5 represents the wavelength dispersion characteristic curve of the optical transmission pathway example 1 of the embodiment of the invention 1.

Fig. 6 represents the wavelength dispersion characteristic curve of example 2 of the optical transmission pathway of the embodiment of the invention 1.

Fig. 7 (a) and (b) be the key diagram that embodiment 2 (the 4 stratotype core) refractive index curve of expression optical fiber of the present invention constitutes (a) and profile of optic fibre structure (b).

Fig. 8 (a) and (b) be the key diagram that embodiment 2 (the 5 stratotype core) refractive index curve of expression optical fiber of the present invention constitutes (a) and profile of optic fibre structure (b).

Fig. 9 is the diagram of the fiber optic wavelength dispersing characteristic example of the expression embodiment of the invention 2.

Figure 10 (a) and (b) be the key diagram that expression optical fiber embodiment 3 refractive index curve of the present invention constitute (a) and profile of optic fibre structure (b).

Figure 11 represents the diagram of analog result of the fiber optic wavelength dispersing characteristic of the embodiment of the invention 3.

Figure 12 is illustrated in and adds Raman's excitation frequency band zone among Figure 11 (1360～1525nm), being illustrated in Raman's excitation frequency band zone dispersion value simultaneously is the diagram of the optical fiber dispersing characteristic of 2～8 (ps/nm/km).

Figure 13 represents the diagram of the fiber optic wavelength dispersing characteristic example of the embodiment of the invention 3.

Figure 14 represents the diagram of the optical communication system structure of embodiment of the present invention.

Figure 15 represents the diagram of the optical communication system structure of other execution modes of the present invention.

Figure 16 represents the diagram of the optical communication system structure of another execution mode of the present invention.

Figure 17 (a) and (b) be the key diagram that expression optical fiber embodiment 4 refractive index curve of the present invention constitute (a) and profile of optic fibre structure (b).

The different curve of loss deviation that the optical fiber that Figure 18 represents the embodiment of the invention 4 causes in the transmission loss difference of 1385nm.

The optical fiber of Figure 19 (a) and (b) expression embodiment of the invention 4 is at the dependence curve of different transmission losses that cause of the transmission loss of 1385nm and wavelength, Figure 19 (a) is in the transmission loss of 1385nm being the example below the 1.5dB/km, and Figure 19 (b) is in the transmission loss of the 1385nm example greater than 1.5dB/km.

The fibre parent material outer surface that Figure 20 represents the embodiment of the invention 3 is with fluoric acid amount of pruning and the optical fiber that obtains the thus relation curve in the transmission loss of 1385nm.

Figure 21 represents the optical fiber interdependence of the embodiment of the invention 4 simultaneously and disperses to tilt to disperse in the big optical fiber curve of wavelength interdependence relation.

The optical fiber of Figure 22 (a)～(c) expression embodiment of the invention 4 disperses the curve of wavelength interdependence.

Figure 23 represents the key diagram of the place ahead to the Raman's amplification wavelength segmentation multiplex system example that excites.

Figure 24 represents the key diagram of rear to the Raman's amplification wavelength segmentation multiplex system example that excites.

Figure 25 represents the key diagram of the two-way Raman's amplification wavelength segmentation multiplex system example that excites.

Figure 26 represents that the diffusing wavelength of the zero of existing fiber and exciting light and signal light wavelength concern the key diagram of example.

The n of Figure 27 optical fiber ₂/ A _EffCurve with the flashlight input and output strength relationship of optical fiber.

The curve of the relation that the pulse that the dispersion absolute value of Figure 28 optical fiber and dispersion cause is widened.

Embodiment embodiment 1

Embodiments of the invention 1 are described below with reference to the accompanying drawings.

Fig. 1 (a) is the refractive index curve structure of expression optical fiber embodiment 1 of the present invention.Fig. 1 (b) is this profile of optic fibre structure of expression.As the Refractive Index Profile o curve refractive index curve of wide range of forms can be arranged, in embodiment 1, distribution shape is more simple, and the design of refraction index profile, control have been adopted the refractive index curve shown in figure (a) easily.

The periphery of the optical fiber core 11 of embodiment 1 covers with clad 7, and above-mentioned core 11 will have the 1st glassy layer 1 of core at least and cover the 2nd glassy layer 2 of this 1st glassy layer periphery.With the above-mentioned clad 7 of above-mentioned the 1st glassy layer 1 is that the refractive indices 1 of benchmark is more than 0.6%, below 1.6%, is that the refractive indices 2 of benchmark is a negative value with the above-mentioned clad 7 of above-mentioned the 2nd glassy layer 2.The diameter of the 1st glassy layer 1 is a, and the diameter of the 2nd glassy layer 2 is b.

In addition, in this manual, the refractive index n of the 1st glassy layer ₁, the 2nd glassy layer refractive index n ₂, the n glassy layer refractive index n _n, metalclad refractive index n _cDuring expression, above-mentioned each refractive indices 1, Δ 2, approximate following (several 3), (several 4), (several 5) of being defined as of Δ n.

Δ1(％)＝{(n ₁ ²-n _c ²)/2×n _c ²}×100………(3)

Δ2(％)＝{(n ₂ ²-n _c ²)/2×n _c ²}×100………(4)

Δn(％)＝{(n _n ²-n _c ²)/2×n _c ²}×100………(5)

The structure of in table 1, having represented optical fiber #-1～#-14 of embodiment 1, each optical fiber the value of above-mentioned each refractive indices 1, Δ 2 as the value that is illustrated in the table 1.The unit of these Δs 1, Δ 2 is %.In addition, the increment of the refringence that the germanium of the 1st glassy layer 1 (Ge) coating causes uses Δ 1 (F) to represent with Δ 1 (Ge) expression, the increment of the refringence that the fluorine of the 1st glassy layer 1 (F) coating causes.

Table 1

	??Δ1 ??(Ge) ??％	??Δ1 ??(F) ??％	??Δ1 ?Total ??％	??Δ2 ??％	??a ??μm	???b ??μm	Disperse ps/km/nm			Disperse inclination ps/km/nm	Transmission loss dB/km		???MFD ???μm ??1550n ????m	???PMI ??ps/km	?n 2/Aeff ?10 -10/w	Bending loses dB/m 1550nm	Cut-off wavelength nm
																		??1360nm	???1430nm	???1625nm	????1550nm	??1390nm	??1550nm
							??#1-1	??0.60	????--	??0.60	??-0.45	??6.1												??14.1	????0.51	?????4.13	?????6.92	?????0.009	???0.612	????0.202	???6.3	????0.19	????8.6	????4.8	????890
??#1-2	??0.60	????--	??0.60	??-0.30	??6.4	??13.9							???-0.17	?????2.79	?????8.57	?????0.026	???0.651	????0.206	???6.79	????0.08	????7.4	????3.7	????916
							??#1-3	??0.70	????--	??0.70	??-0.30	??4.9												??15.8	???-3.04	?????0.88	?????7.96	?????0.033	???0.668	????0.208	???6.08	????0.11	????9.9	????2.2	????935
??#1-4	??0.70	????--	??0.70	??-0.40	??5.7	??11.9							???-0.52	?????3.05	?????8.29	?????0.023	???0.664	????0.211	???6.11	????0.15	????9.8	????1.1	????982
							??#1-5	??0.70	????--	??0.70	??-0.40	??5.2												??12.1	???-5.46	????-3.01	????-5.89	????-0.002	???0.697	????0.207	???5.99	????0.13	????10.1	????4.3	????870
??#1-6	??0.90	????--	??0.90	??-0.40	??4.4	??11.7							???-8.73	????-6.10	????-5.74	????-0.003	???0.717	????0.222	???5.40	????0.42	????14.0	????1.6	????896
							??#1-7	??1.00	????--	??1.00	??-0.40	??4.4												??11.8	???-8.90	????-6.03	????-3.38	?????0.009	???0.728	????0.234	???5.19	????0.35	????16.0	????0.7	????925
??#1-8	??0.80	????--	??0.80	??-0.40	??4.9	??11.9							???-5.98	????-3.20	????-2.37	????-0.001	???0.674	????0.211	???5.68	????0.04	????12.0	????3.2	????820
							??#1-9	??1.20	????--	??1.20	??-0.55	??5.0												??12.4	???-3.31	?????0.59	?????7.53	?????0.032	???0.810	????0.235	???4.90	????0.03	????19.8	????0.5	????1010
??#1-10	??1.40	????--	??1.40	??-0.55	??4.6	??10.9							???-2.42	?????1.31	?????7.89	?????0.030	???0.880	????0.242	???4.60	????0.15	????24.5	????0.2	????1118
							??#1-11	??1.60	????--	??1.60	??-0.55	??4.7												??11.1	???-2.79	?????1.11	?????8.32	?????0.034	???0.950	????0.247	???4.43	????0.18	????28.7	????0.1	????1166
??#1-12	??1.10	??-0.40	??0.70	??-0.40	??5.8	??11.9							???-0.60	?????3.12	?????8.43	?????0.024	???0.490	????0.212	???6.01	????0.19	????12.5	????0.9	????996
							??#1-13	??1.05	??-0.45	??0.60	??-0.45	??6.0												??14.0	????0.52	?????4.14	?????7.06	?????0.009	???0.480	????0.215	???6.27	????0.22	????11.2	????4.7	????902
??#1-14	??1.05	??-0.45	??0.60	??-0.45	??6.1	??14.1							????0.53	?????4.08	?????7.11	?????0.009	???0.450	????0.216	???6.29	????0.18	????11.2	????4.9	????889

In addition, in table 1, a represents the diameter of the 1st glassy layer 1, and b represents the diameter of the 2nd glassy layer 2.Dispersion is the wavelength dispersion in the interior wavelength of parantheses, and MFD is the mode field diameter at wavelength 1550nm, and PFD disperses in the polarized wave form of wavelength 1550nm, and bending loses is the bending loses at the φ of wavelength 1550nm 20mm.Cut-off wavelength is a cable cut-off wavelength, just the cut-off wavelength when the length of optical fiber is 22m.

The host glass of the optical fiber of embodiment 1 is quartzy.Just the optical fiber of embodiment 1 is to be that glass forms by quartz.One of optical fiber example of embodiment 1 is, the 1st glassy layer 1 will add germanium at least, and the 2nd glassy layer 2 will add fluorine at least.For example optical fiber shown in the #1-1～#1-11 in the table 1 is exactly the structured optical fiber of this example.

The example of the optical fiber of another embodiment 1 is, the 1st glassy layer 1 will add germanium and fluorine at least, and the 2nd glassy layer 2 will add fluorine at least.For example optical fiber shown in the #1-12～#1-14 in the table 1 is exactly the optical fiber of this example structure.The fluorinated volume of the fluorinated volume of the 1st glassy layer 1 and the 2nd glassy layer 2 is identical substantially in the structure of these examples.

As shown in table 1, the optical fiber of embodiment 1 in the transmission loss of wavelength 1550nm all below 0.25dB/km.

Transmission loss for example is used under the situation of long Distance Transmission path of 80km, for the damage control of transmission channel in 20dB, must be below the 0.25Db/km.Owing to carry out Raman's amplification, can cover some losses, consider noise etc. take place that the loss in the signal area will be limited in the 0.25Db/km.

As mentioned above, the optical fiber of embodiment 1 is owing to being decided to be the transmission loss of wavelength 1550nm below the 0.25dB/km, so go for the long Distance Transmission of wavelength 1.55 μ m frequency bands.

In addition, the optical fiber of embodiment 1 is decided to be the transmission loss of wavelength 1385nm below the 1.0dB/km.

Have near the absorption loss water that causes because of the OH base wavelength 1385nm in optical fiber, this loss does not have too big problem to optical fiber when C-band uses, just become problem when S-band is used.

Just in the optical transmission pathway of using with Raman's amplification of S-band, use under the situation of optical fiber, overlapping near the wavelength 1385nm with the excitation wavelength band, so near wavelength 1385nm absorption loss water is arranged, the loss of exciting light takes place.The loss of wavelength 1385nm is big above the loss of the optical fiber exciting light of 1dB, needs the light source of high price and big electric power, has the cost problem.

The optical fiber of embodiment 1 is owing to be decided to be the transmission loss of wavelength 1385nm below the 1.0dB/km, so even optical fiber is used for the optical transmission pathway that Raman's amplification of S-band is used, the exciting light that also can suppress wavelength 1385nm loses.

In addition, the loss of the wavelength 1385nm of the optical fiber of embodiment 1 under the hydrogen environment will increase below 10%.The hydrogen experimental condition is pressed IEC60793-2 Amendment 1,2001-8 Annex B, and losing increase in this specification under the hydrogen environment is to mean above-mentioned connotation.

The loss of the wavelength 1385nm that the hydrogen of generation causes in the optical cable now increases the words more than 10%, have the power of the exciting light that does not increase the input optical transmission pathway, and the problem that system will reduce, and embodiment 1 is because the wavelength 1385nm loss increase under the hydrogen environment will can be avoided this problem below 10%.

In addition, the optical fiber of embodiment 1 all makes the polarized wave form be dispersed in below the 0.5ps/  km.

The polarized wave form disperses influence high-speed transfer, and the value that the polarized wave form is disperseed is with generally optical cable is identical, not at 0.5ps/  km with interior, it is impossible then not having the high-speed transfer of polarized wave form dispersion compensation.

The optical fiber of embodiment 1 disperses so suppressed the polarized wave form owing to all the polarized wave form is dispersed in below the 0.5ps/  km, also can high-speed transfer even without polarized wave form dispersion compensation.

Particularly show the optical fiber shown in 1#1-1～#1-5, #1-8～#1-12, the #1-14 because the polarized wave form is dispersed in below the 0.2ps/  km, further suppress the baneful influence that the dispersion of polarized wave form causes, also can carry out the high-speed transfer of 40GB/s level even without polarized wave form dispersion compensation.

Be the optical fiber shown in table 1#1-1, #1-13, the #1-14 make in wavelength region-wide from 1360nm to 1625nm wavelength dispersion on the occasion of, and the absolute value that makes dispersion is more than the 0.5ps/nm/km, below the 9ps/nm/km, do not have the zero wavelength that looses in this wide wave-length coverage.

Just, for example resemble shown in the characteristic curve a of (a) of Fig. 2, than exciting light R _1～mMinimal wave length R ₁(is 1360nm at this) shorter shortwave one side is the structure that the diffusing wavelength of zero is arranged.

In addition, it is negative value that optical fiber shown in table 1#1-5～1-8 makes the region-wide interior wavelength dispersion of wavelength from 1360nm to 1625nm, and the absolute value that makes dispersion is more than the 0.5ps/nm/km, below the 9ps/nm/km, do not have the zero wavelength that looses in this wide wave-length coverage.

Just, for example resemble shown in the characteristic curve a of Fig. 3, than flashlight S _1～nLong wavelength S _n(is 1625nm at this) longer long wave one side is the structure that the diffusing wavelength of zero is arranged.

Fiber optic wavelength dispersing characteristic among Fig. 4 shown in #1-1, the #1-5 is the representational example of these optical fiber.Characteristic curve a represents the wavelength dispersion characteristic of above-mentioned #1-1, and the characteristic curve b of this figure represents the wavelength dispersion characteristic of above-mentioned #1-5.

As mentioned above, these optical fiber are not owing to there is the zero wavelength that looses in from 1360nm to the 1625nm scope, in wide wave-length coverage (wavelength is from 1460nm to 1625nm) from the wavelength S-band to L-band, do not produce because of four light waves mix the efficient that causes and reduce, can be suitable for the wavelength segmentation multiplexing of Raman's amplification effectively.

The dispersion absolute value that the optical fiber of table shown in 1#1-2～#1-4, the #1-9～#1-12 makes the whole zone of wavelength from 1430nm to 1625nm is more than the 0.5ps/nm/km, below the 9ps/nm/km, do not have the zero wavelength that looses in this wide wave-length coverage.

Just, for example resemble shown in the characteristic curve a of (b) of Fig. 2, than exciting light R _1～mMinimal wave length R ₁(is 1430nm at this) shorter shortwave one side is the structure that the diffusing wavelength of zero is arranged.

Just, these optical fiber do not produce because of four light waves mix the efficient that causes and reduce in the wave-length coverage of C-band and L-band, can be suitable for the wavelength segmentation multiplexing of Raman's amplification effectively.

In addition, the optical fiber of embodiment 1 can suppress to broaden because of the pulse that disperses to cause owing to make wavelength dispersion absolute value in the whole zone of wavelength from 1360nm to 1625nm below 9ps/nm/km, can reduce the nonlinear effect of intersymbol.

When carrying out high speed wavelength segmentation multiplexing about 40Gb/s with Raman's amplification, even it is for example all little as the dispersion of the optical fiber unit length of optical transmission pathway, but its accumulation disperses to surpass 60ps/nm, because the waveform severe exacerbation must carry out dispersion compensation.

Be transmitted as with the broadband territory under the situation of purpose, preferred single dispersion compensator carries out dispersion compensation at wide band.Also be difficult to compensate rapid dispersion at the favourable dispersion-compensating fiber of wide band and tilt, the ratio (DPS:Dispersion/Disoersion Slope) that is difficult to accomplish the dispersion of hope and disperse inclination is below 200 (nm).

Therefore, for example the optical fiber that disperses absolute value 8～9ps/nm/km is used under the optical transmission pathway situation, this optical fiber disperse the absolute value that tilts with 0.04ps/nm ²/ km scatter pay is identical, and the handlebar optical fiber that disperses absolute value to drop to about 4～6ps/nm/km is used under the situation of optical transmission pathway again, wishes that it is same symbol that this optical fiber disperses inclination absolute value, at 0.03ps/nm ²Below/the km.

The dispersion inclination absolute value of the fiber optic wavelength 1550nm of embodiment 1 is all at 0.04ps/nm ²Below/the km, can satisfy above-mentioned condition, disperse variation little, can realize the optical fiber of easy dispersion compensation in the scope of non-constant width.

The core cross-sectional area of actual effect is single corresponding with mode field diameter, if actual effect core cross-sectional area is excessive, can not get enough Raman's amplification efficient.The mode field diameter of ITU-T suggestion dispersion deflection optical fiber (DSF) G.653 is decided to be 7.8～8.5 μ m, has the actual effect core cross-sectional area minimum of the optical fiber of this mode field diameter, at 48 μ m ²About.

Amplify in order to obtain the Raman bigger than this dispersion deflection optical fiber, the actual effect core cross-sectional area of preferred fiber is at 40 μ m ²Below.The mode field diameter of corresponding this actual effect core cross-sectional area is below 7 μ m.

And the optical fiber of embodiment 1 because the mode field diameter of wavelength 1550nm all fixes on below the 7 μ m, so can more effectively carry out Raman's amplification than above-mentioned dispersion deflection optical fiber, can be realized the wavelength segmentation multiplexing that suits.

In addition, the optical fiber of embodiment 1 is owing to making cable cut-off wavelength all less than 1360nm, so can satisfy the single-mode condition for exciting light and flashlight.

In addition, the bending loses of the φ 20mm of the fiber optic wavelength 1550nm of embodiment 1 is all below 5dB/m.If optical fiber has this value, can constitute from S-band to the L-band scope in operable optical cable, the optical fiber of embodiment 1 can constitute the little optical cable of loss in wide wave-length coverage.

The inventor has carried out research miscellaneous when definite embodiment 1 optical fibre refractivity curve.It found that, as shown in Figure 1, is negative value by making refractive indices 2, can realize making the optical fiber that disperses the inclination absolute value to reduce.

In addition, when birefringence rate variance Δ 1 was studied, if find to make refractive indices be lower than 0.6%, the mode field diameter of wavelength 1550nm can not be below 7 μ m, if make refractive indices 1 greater than 1.6%, the transmission loss of wavelength 1550nm is greater than 0.25dB/km.

As mentioned above, make refractive indices 1 more than 0.6%, below 1.6%, make refractive indices 2 be negative value, determine embodiment 1 optical fibre refractivity curve, routine various optical fiber as shown in table 1 have been made in test.

In addition, the inventor has carried out various researchs to the synthetic method of optical fiber, and the formation shown in below having determined is a preferred embodiment 1.Being characterized as of this 1st topology example just, the 1st glassy layer 1 and the 2nd glassy layer 2 are synthetic simultaneously.Being characterized as of the 2nd topology example, clad 7 is synthetic simultaneously with the 1st glassy layer 1 and the 2nd glassy layer 2 from the regional extent more than 2 times (for example in the frame of broken lines of Fig. 1 (b)) of border to the 2 glassy layers, 2 diameters of the 2nd glassy layer 2.

Above-mentioned preferred construction example is #1-13 and #1-14 in the table 1, and #1-13 is the example of the 1st structure, and #1-14 is the example of the 2nd structure.

The optical fiber of embodiment 1 all has the refractive index curve identical with Fig. 1.But #1-1 is that the 1st glassy layer 1 and the 2nd glassy layer 2 are separate synthetic, and #1-13 is that the 1st glassy layer 1 and the 2nd glassy layer 2 are synthetic simultaneously.In addition, #1-14 be the 1st glassy layer 1 and the 2nd glassy layer 2 with clad 7 in from synthetic simultaneously with the scope in zone more than 2 times of the 2nd glassy layer 2 borders to the 2 glassy layers, 2 diameters.

If use the structure of #1-13, #1-14, owing to do not have the interface in the core, can reduce the loss that the OH base causes, can reduce the transmission loss of wavelength 1385nm.The transmission loss value of wavelength 1385nm, even the value in the optical fiber of #1-1 also reaches no problem level, but the value of the optical fiber of #1-13, #1-14 preferably.

In addition, the optical fiber of #1-14 is because the clad 7 of a part is synthetic with core 11, can be littler than the value of the transmission loss of wavelength 1385nm.

Have again, when #1-1 and #1-14 compare, although mode field diameter is much at one, n ₂/ A _EffAlso different.Because added germanium and fluorine together in the 1st glassy layer 1 of #1-14, the #1-1 identical with the refractive index of the 1st glassy layer 1 compares, the impurity concentration height of the 1st glassy layer 1, n ₂Greatly.So n of #1-14 ₂/ A _EffN than #1-1 ₂/ A _EffCan bring into play the effect that increases Raman's amplification coefficient greatly.

Below, the embodiment of the optical transmission pathway of embodiments of the invention 1 is described.For example, represented this transmission channel in 11 of Figure 23～Figure 25.The optical transmission pathway of embodiment 1 vertically is formed by connecting by the optical fiber of the #1-1 shown in the table 1 and the optical fiber of #1-7.The optical fiber of #1-1 is located at a side that sends flashlight, and the optical fiber of #1-7 is located at a side of received signal light, and the length ratio of the length of the optical fiber of #1-1 and the optical fiber of #1-7 is 1: 1.6.

With the viewpoint that accumulation disperses, preferably with the optical fiber of positive dispersion value and the optical fiber of negative dispersion value, optical fiber and the negative optical fiber that disperses that having more than 1 just disperseed make up, and form optical transmission pathway, and the optical transmission pathway of embodiment 1 is suitable for this structure.

The average dispersing characteristic of this optical transmission pathway of expression in Fig. 5.Because the average dispersion value of optical transmission pathway is open to discussion in the signal light wavelength scope of 1460nm～1625nm to the not influence of wave-length coverage of exciting light.As shown in Figure 5, almost nil in the average dispersion of this scope.

In addition the optical transmission pathway of embodiment 1 the average dispersion value of the wavelength domain of setting in wavelength 1460nm～1625nm scope (is full wavelength domain at this) is decided to be-more than the 1.0ps/nm/km, below the 1.0ps/nm/km.The dispersion value of wavelength 1460nm is-1ps/nm/km, the full wavelength domain dispersion value below wavelength 1625nm+below the 1ps/nm/km.

Like this, the absolute value of the average dispersion of the optical transmission pathway of embodiment 1 in S, C, L-band scope is below the 1ps/nm/km, can suppress wave distortion in S, C, the whole zone of L, can realize the optical transmission pathway that wavelength segmentation multiplexing is used.

Therefore, by being suitable for this optical transmission pathway, the average dispersion value that can form the setting wave-length coverage (this be this wavelength domain) of wavelength in from 1460nm to the 1625nm scope is at-optical transmission system more than the 1.0ps/nm/km, below the 1.0ps/nm/km.

This optical transmission system as Figure 23～shown in Figure 25, is connected to form signal source and exciting light source and optical transmission pathway, exciting light source output and exciting light from the flashlight different wave length of this signal source output.The place ahead to excite, the rear to excite, two-way exciting all be suitable for.

The optical transmission pathway of embodiment 1 the wavelength domain of above-mentioned setting as full wavelength domain, and the wavelength domain that the wavelength domain of setting can only be to use can form the setting wavelength domain of part setting or the optical transmission pathway of dispersion value below 1ps/nm/km of setting wavelength like this.

In compound transmission channel, be suitable for the rear under the situation of the Raman's amplification that excites (counter propagationpumping), Raman is amplified little received signal light one side that is arranged on, be difficult to obtain amplify.Therefore in the multifiber that forms optical transmission pathway, the optical fiber of mode field diameter maximum can be arranged on and remove on other positions of the most close received signal light one side position.

The average dispersing characteristic of the example 2 of the optical transmission pathway of the embodiments of the invention of representing at Fig. 61.This optical transmission pathway is that the dispersion compensation by the optical fiber of above-mentioned #1-1 and single-mode optical fiber combined than 12: 1 by length with dispersion-compensating fiber.

The dispersion value of dispersion-compensating fiber wavelength 1460nm that is applicable to the optical transmission pathway of example 2 is-72ps/nm/km, and the dispersion value of wavelength 1550nm is-80ps/nm/km that the dispersion value of wavelength 1625nm is-94ps/nm/km.

The average dispersion value of the wavelength domain that the optical transmission pathway of example 2 is set wavelength in from 1460nm to the 1625nm scope (being full wavelength domain at this) is decided to be-more than the 1.0ps/nm/km, below the 1.0ps/nm/km.Can obtain the effect same with the optical transmission pathway of above-mentioned example 1.In addition, the optical transmission system that is applicable to the optical transmission pathway of example 2 also has identical effect with the optical transmission system of the optical transmission pathway that is applicable to above-mentioned example 1.

In the optical transmission pathway of example 2, maximum on average is separated into+0.96ps/nm/km (value of wavelength 1540nm), and minimum average B configuration is separated into-0.92ps/nm/km (value of wavelength 1625nm).

Embodiment 1 does not limit above-mentioned each optical fiber, optical transmission pathway, can adopt various execution modes.For example the optical fiber of embodiment 1 have above-mentioned shown in beyond refractive index curve also passable, the transmission channel of embodiment 1 is in optical fiber of the present invention, by the optical fiber that is just disperseing and have the negative optical fiber that disperses respectively each 1 above appropriate combination form.

Optical transmission system of the present invention can make the average dispersion value of the wavelength domain that wavelength sets in from 1460nm to the 1625nm scope be decided to be-more than the 1.0ps/nm/km, below the 1.0ps/nm/km.Above-mentioned wavelength set scope also can be a part of wavelength domain of wavelength in from 1460nm to the 1625nm scope.

The optical fiber, optical transmission pathway and the optical transmission system that use with the wavelength segmentation multiplexing of Raman's amplification in above-mentioned example, have been narrated, and optical fiber of the present invention, optical transmission pathway and optical transmission system for example also go for the wavelength segmentation multiplexing with the optical-fiber type light amplifier that adds erbium except Raman's amplifier.Embodiment 2

The diffusing wavelength of the zero of the optical fiber of embodiments of the invention 2 is below the 1350nm, in the wide band of 1400～1700nm, can suppress FWM and take place, and have the dispersing characteristic that can suppress the accumulation dispersion.Reduction in the scheme that this prerequisite is crossed disperses to have at S, C, L-band (1460～1625nm) dispersing characteristics that can transmit among the apsacline NZ-DSF, (1625～1675nm) (1360～1460nm) entirely with the more wide band in territory (in 1365～1700nm) with the E-wave band of territory, shortwave one side entirely but the optical fiber of embodiment 2 almost comprises the U-wave band of long wave one side in whole zone, dispersion value D is 2≤D≤8 (ps/nm/km), can suppress FWM and take place, and have the dispersing characteristic that can suppress the accumulation dispersion.

When setting about the optical fiber of embodiment 2 used as transmission channel, in S, C, L-wave band in the amplification at least one wave band band territory, by profile Raman amplifier and concentrated amplifier and usefulness, can compensate S, C, L-wave band entirely with territory (1460～1625nm) loss.By making as transmission channel dispersion inclination is zero, wavelength is compared with the diffusing wavelength of the zero that reduces the NZ-DSF that disperses apsacline and is also further shifted to shortwave one side (below the 1360nm even zero is loose, preferably below 1340nm), even so the flashlight amplification that is used to make the S-wave band Raman's excitation band territory, also can suppress the interference that generation caused of FWM.

In addition, EDFA (Erbium Doped Fiber Amplifier), TDFA (Thuliumdoped Fiber Amplifier) and concentrated Raman amplifier and time spent, in order to suppress the impairment that non-linear phenomena causes, the effective core cross-sectional area Aeff that makes 1550nm is at 40 μ m ²More than (preferred 45 μ m ²More than).In addition, in order to do the single-mode action with the C-band transmission at least, make cable cut-off wavelength below 1550nm.Consider optical cableization, make bending loses under the diameter 20mm of wavelength 1550nm below 5dB/m.

The transmission channel that optical communication system is made up of the optical fiber with above-mentioned dispersing characteristic, the S-wave band that is located in the transmission channel constitute with distribution Raman amplifier.Constitute optical communication system by optical fiber, can realize to carry out the good optical communication system of high-quality WDM transmission with embodiment 2.Be particularly suitable at the communication system of subway optical fiber such, that compare short-distance transmission.

With reference to the accompanying drawings the embodiment of the invention 2 is described below.

(a) of Fig. 7, Fig. 8 represents the refractive index distribution curve of the embodiment 2 of optical fiber of the present invention, represents the section structure of this optical fiber at (b) of Fig. 7, Fig. 8.As the Refractive Index Profile o curve, the refractive index distribution curve of wide range of forms can be arranged, among the embodiment 2, as expression in Fig. 7 (a), Fig. 8 (a), adopted the refractive index curve of 4 layers of structure and 5 layers of structure.

As shown in Figure 7, optical fiber with refractive index curve covers core 11 with clad 7, above-mentioned core 11 is made of the glassy layer of forming different multilayers (4 layers) between adjacent (the 1st glassy layer the 1, the 2nd glassy layer the 2, the 3rd glassy layer the 3, the 4th glassy layer 4) at least, and these glassy layers become concentric garden shape.Clad with respect to above-mentioned 4 layers of glassy layer be as the refraction index profile benchmark the layer, be benchmark with it.

The optical fiber of 4 layers of structure of embodiment 2 is being defined as respectively with respect to metalclad refringence: the 1st glassy layer 1: Δ the 1, the 2nd glassy layer 2: Δ the 2, the 3rd glassy layer 3: Δ the 3, the 4th glassy layer 4: under the situation of Δ 4, become Δ 1＞Δ 3＞Δ 4＞0＞Δ 2 (metalclad Δ as 0).In addition, the refractive index profile shape of the 1st glassy layer 1 is rendered as α power (with reference to the formula of introducing later (6)).

Fig. 8 represents another refractive index curve of embodiment 2.As shown in Figure 8, optical fiber with refraction index profile covers core 11 with clad 7, above-mentioned core 11 is made of the glassy layer of forming different multilayers (5 layers) between adjacent (the 1st glassy layer the 1, the 2nd glassy layer the 2, the 3rd glassy layer the 3, the 4th glassy layer the 4, the 5th glassy layer 5) at least, and these glassy layers become concentric garden shape.

The optical fiber of 5 layers of structure of embodiment 2 is being defined as respectively with respect to metalclad refringence: the 1st glassy layer 1: Δ the 1, the 2nd glassy layer 2: Δ the 2, the 3rd glassy layer 3: Δ the 3, the 4th glassy layer 4: Δ the 4, the 5th glassy layer 5: under the situation of Δ 5, become Δ 1＞Δ 4＞Δ 5＞0＞Δ 3＞Δ 2.In addition, the refractive index profile shape of the 1st glassy layer 1 is rendered as the α power.Compare with the curve of Fig. 7, difference is that the layer of refractive index ratio clad low (Δ becomes negative sign) has increased by one.

As Fig. 7, shown in Figure 8, the 1st layer diameter is defined as a, the 2nd layer diameter is defined as b, below in order the 3rd, 4,5 layer diameter is defined as c, d, e respectively.

In Fig. 7, the refractive index curve shown in Figure 8, the refractive index profile shape α of each refractive indices 1, Δ 2, Δ 3, Δ 4, Δ 5 and the 1st glassy layer 1, diameter a, the b of each layer, c, d, e are simulated as parameter, ask optimum solution.As this moment condition dispersion value D satisfy above-mentioned dispersing characteristic (at wavelength 1400nm～1700nm, 2≤D≤8 (ps/nm/km)), satisfy Aeff (at wavelength 1550nm, 40 μ m ²More than) condition, (at wavelength 1550nm, condition 5dB/m) satisfies cut-off wavelength in the cut-off wavelength of the actual fiber optical cable condition at 1550nm to the bending loses value, makes the optimal curve of embodiment 2 with such finding the solution.This design content is expressed as #2-1 in the table 2, #2-2 and #2-3.

Table 2

	??Δ1	??Δ2	??Δ3	??Δ4	??Δ5	?α	??????????????????a∶b∶c∶d∶e					????Dc	????λ	?????DP	??????S	??Aeff	????λc	???BL
																				??％	??％	??％	??％	??％		????a	????b	????c	????d	????e	????μm	????nm	???ps/nm/km	???ps/nm 2/km	??μm 2	????nm	??dB/m
?#2-1	??0.48	??-0.46	??-0.05	??0.4	??0.19	?10	????1	????1.7	???2.2	????2.6	????2.7	????20.0	??1500	????6.58	????0.0085	??42.0	??＜1550	??＜1
																			??1550	????6.62	????-0.0067	??44.6	????2
													?#2-2	??0.48	??-0.46	??-0.05		??0.39						??0.19	?10	????1	????1.7	???2.2	????2.6	????2.7	????20.2	??1500	????7.17	????0.0107	??42.1	??＜1550	??＜1
??1550	????7.3	????-0.0044	??44.7	????2
					?#2-3	??0.5	??-0.55	???0.38	???0.2	??---	??8	??1					????1.7		???2.1	????2.6	????---	????20.0	??1500									????5.42	????0.0079	??43.5	??＜1550		??＜1
??1550	????5.56	????-0.0019	??46.5	????1

Dc: core diameter

λ: wavelength

DS: disperse

D: disperse to tilt

Aeff: effective area

λ c: cable cut-off wavelength

BL: bending loses

In embodiment 2, the dispersion value D of wavelength 1400nm～1700nm is 2≤D≤8 (ps/nm/km), and be used in the optical fiber that identical wave band zone wavelength dispersion has 1 extreme value at least, there is not dispersion compensator can realize the WDM transmission basically yet, have again, also comprise the flashlight distribution Raman amplification that makes the S-wave band, also can be in the amplification of wide band than being easier to.

Characteristic, structure as the optical fiber of embodiment 2, preferred value is: the dispersion value D of wavelength 1310nm is-4≤D≤4 (ps/nm/km), cable cut-off wavelength is below 1550nm, bending loses under the diameter 20mm of wavelength 1550nM is below 5dB/m, and the actual effect core cross-sectional area of wavelength 1550nm is at 40 μ m ²More than, it is below the 0.1ps/  km that the polarised light form of wavelength 1550nm is disperseed PMD, the dispersion value D of wavelength 1310nm is-2≤D≤2 (ps/nm/km), and zero is loose wavelength below 1350nm.

Can select clad with respect to the 1st the most inboard glassy layer as an example in the optical fiber of 4 layers of structure of Fig. 7, refractive indices 1 is 0.3～0.7%, and during with the fiber of diameter 125 μ m, the diameter of the 1st glassy layer is 7.0～10.0 μ m.

In addition as shown in Figure 7, for the 1st glassy layer 1, have the refraction index profile of following formula (6) expression from the radius of central shaft, the index α of expression refractive index is decided to be more than 4.In this manual the index α of expression refractive index profile shape is defined with following formula

n ²(r)＝n1 ²{1-2·Δ1·(2r/a) ^α}……………(6)

But 0≤r≤a/2

Wherein r is fibre diameter direction position.The refractive index of n (r) expression position r.

Can select with respect to the clad from the 2nd layer the 2nd glassy layer of inboard number as an example in the optical fiber of 4 layers of structure of Fig. 7, refractive indices 2 is-0.6～-0.2%, and the 2nd layer of diameter is 1.2～1.7 times with respect to the 1st layer of diameter; From the clad of the 3rd layer the 3rd glassy layer of inboard number, refractive indices 3 is that the 0.25～0.5%, 3rd layer of diameter is 1.8～2.2 times with respect to the 1st layer of diameter; And from the clad of the 4th layer the 4th glassy layer of inboard number, refractive indices 4 is that the 0.05～0.2%, 4th layer of diameter is 2.0～2.5 times with respect to the 1st layer of diameter.

Can select clad as an example in the optical fiber of 5 layers of structure of Fig. 8 with respect to the 1st the most inboard glassy layer, refractive indices 1 is 0.3～0.7%, the constant alpha of expression refractive index profile shape is more than 4, and the diameter of the 1st glassy layer is 6.5～10 μ m during with the fiber of diameter 125 μ m.

Can select with respect to the clad from the 2nd layer the 2nd glassy layer of inboard number as an example in the optical fiber of the sandwich construction of Fig. 8, refractive indices 2 is-0.6～-0.2%, and the 2nd layer of diameter is 1.2～1.7 times with respect to the 1st layer of diameter; From the clad of the 3rd layer the 3rd glassy layer of inboard number, refractive indices 3 is-0.15～-0.05%, and the 3rd layer of diameter is 1.8～2.2 times with respect to the 1st layer of diameter; From the clad of the 4th layer the 4th glassy layer of inboard number, refractive indices 4 is that the 0.25～0.65%, 4th layer of diameter is 2.0～2.5 times with respect to the 1st layer of diameter; And from the clad of the 5th layer the 5th glassy layer of inboard number, refractive indices 5 is that the 0.05～0.50%, 5th layer of diameter is 2.2～3.0 times with respect to the 1st layer of diameter.

When the optical fiber of embodiment 2 is used for optical transmission pathway, the constituting profile Raman amplifier and have a band territory at least and use the concentrated amplifier of optical communication system at S, C, L-wave band.

Make the optical fiber of embodiment 2 by the content shown in the table 2.Obtain the dispersing characteristic of designing requirement substantially.#2-1, #2-2 are 5 stratotypes of Fig. 8, and #2-3 is 4 stratotypes of Fig. 7.Disperseing in table 2 is the dispersion value of wavelength 1500nm and 1550nm, and inclination is that the dispersion of wavelength 1500nm and 1550nm is tilted, and Aeff is the actual effect core cross-sectional area of wavelength 1500nm and 1550nm, λ _cBe cable cut-off wavelength, bending is the bending loses of the diameter 20mm of wavelength 1500nm and 1550nm, λ ₀Be the diffusing wavelength of zero, the core diameter is the d among Fig. 7, or the diameter of the e among Fig. 8.Fig. 9 is the dispersing characteristic with respect to optical fiber of #2-1, #2-2 and #2-3, as shown in Figure 9, the dispersion value D of 3 wavelength 1400～1700nm of the optical fiber #2-1～#2-3 of table 2 is 2≤D≤8 (ps/nm/km), and in identical wavelength band territory wavelength dispersion extreme value is arranged.(pay close attention to, with wavelength 1500nm on the occasion of opposite, 1550nm becomes negative value at wavelength, is dispersed with extreme value between this).Cable cut-off wavelength is below 1550nm, and the bending loses of the diameter 20mm under the wavelength 1550nm is below 5dB/m.As shown in Figure 9, the diffusing wavelength X of zero ₀Below 1350nm, the S-wave band is expanded in transport tape territory that can Raman's amplification to.Actual effect core cross-sectional area Aeff remains on 40 μ m ²More than (preferably at 45 μ m ²More than), can suppress to resemble the non-linear phenomena of existing DSF.

As shown in Figure 9, the optical fiber of embodiment 2 is being because wavelength dispersion is specifying the band territory to have an extreme value at least because dispersion plot be not resemble existing fiber (#2-4: Reduce and disperse apsacline NZ- DSF-disperses inclination 0.02ps/nm ² / km@1555nm, and #2-5:True Wave (registered trade mark) RS-disperses inclination 0.045ps/nm ²/ km@1550nm) dullness increases or dull the minimizing like that, can suppress FWM, and satisfy to accumulate and disperse the wavelength band territory of the very not big desirable dispersion value of 2～8ps/nm/km to become wideer.(with reference to table 2)

Wherein, the dispersion value of wavelength 1400～1700nm is 2～8ps/nm/km, can suppress FWM in identical wavelength band territory and take place, and also can suppress accumulation and disperse.Therefore do not require basically that in identical wavelength band territory dispersion compensator also can transmit.Among the previously presented NZ-DSF, although it is S, C, L-wave band (1460-1625nm) that band field width (#2-4 of Fig. 9) also limits the transport tape territory, and NZ-DSF of the present invention, have at U-wave band (1625-1675nm), E-wave band (1360-1460nm), add above-mentioned 3 dispersing characteristics that the band territory can be transmitted.Now restriction U-band transmission mainly is the problem that increases of wavelength band territory loss (bending loses, absorb infrared ray), restriction E-band transmission mainly be near the problem of the OH base loss that shows the wavelength 1385nm.Solve this two problems, NZ-DSF of the present invention has can be at the dispersing characteristic of U, E-band transmission.(not needing dispersion compensator basically at the U-wave band), dispersion plot is relatively more flat in addition also is the characteristics of embodiment 2.Particularly in the dispersing characteristic of the #2-3 of Fig. 9, (1460～1625nm) poor dispersion is (below 0.7) below the 1ps/nm/km, we can say that the dispersion at wide band is very flat at S, C, L-wave band.

Even consider to use Raman's amplification, more than 2ps/nm/km, be the dispersing characteristic that to avoid the FWM generation at the dispersion value of the minimal wave length 1350～1360nm in Raman's excitation band territory of S-band transmission in the system that identical optical fiber is being used for transmission channel.Just, exciting the excitation signal light belt territory of Raman's amplification of S-wave band minimal wave length 1460nm is 1350～1360nm, and this optical fiber has about the dispersion 2ps/nm/km of appropriateness in this band territory, can control the FWM between the excitation signal light, can make Raman's amplification of S-wave band.Raman's excitation band territory dispersion value of C, L-band transmission is more than 2ps/nm/km, so the optical fiber of the #2-1～#2-3 of table 2 has at can the distribute dispersing characteristic of Raman's amplification of S, C, L-wave band.

Figure 14, Figure 15 represent to constitute the example of making the optical communication system of transmission channel with the optical fiber of this embodiment 2.

The optical fiber of this embodiment 2 demonstrates the dispersing characteristic that has the Raman's amplification that can distribute in S, C, L-wave band entire belt territory.It is difficult all carrying out Raman's amplification at whole S, C, L-wave band, because transport tape territory and excitation band territory are overlapping.For head it off, for example, with concentrating amplifier or EDFA, can cover the entire belt territory at the L-wave band at S and C-band territory distribution Raman amplifier.Embodiment 3

As shown in figure 10, optical fiber with refractive index curve covers core 11 with clad 7, above-mentioned core 11 is made of the glassy layer of forming different multilayers (4 layers) between adjacent (the 1st glassy layer the 1, the 2nd glassy layer the 2, the 3rd glassy layer the 3, the 4th glassy layer 4) at least, and these glassy layers become concentric garden shape.Clad with respect to above-mentioned 4 layers of glassy layer be as the refraction index profile benchmark the layer, be benchmark with it.

The optical fiber of 4 layers of structure of embodiment 3 is being defined as respectively with respect to metalclad refringence: the 1st glassy layer 1: Δ the 1, the 2nd glassy layer 2: Δ the 2, the 3rd glassy layer 3: Δ the 3, the 4th glassy layer 4: under the situation of Δ 4, be Δ 1＞Δ 4＞Δ 3＞Δ 2.In addition as shown in figure 10, the 1st glassy layer 1 shows as the α power, and the index α of expression refractive index profile shape is more than 4.

It is 0.3～0.7% that the 1st glassy layer 1 is set the largest refractive index difference respectively with respect to clad 7, diameter a be the clad diameter 0.05～0.1 times scope.When therefore for example clad diameter D was 125 μ m, diameter a was set at 6.5～12 μ m.

In addition, the 2nd glassy layer 2, refractive indices 2 is set at respect to-0.6～-0.2% of clad 7, and diameter b is set at 1.3～1.8 times of the 1st glassy layer 1 diameter a.The refractive indices 3 of the 3rd glassy layer 3 is set at respect to-0.2～-0.05% of clad 7, and diameter c is set at 1.9～2.4 times of the 1st glassy layer 1 diameter a.The 4th glassy layer 4 refractive indices 4 are set at respect to metalclad 0.1～0.55%, and diameter d is set at 2.6～2.8 times of the 1st glassy layer 1 diameter a.This moment, the refractive indices 1～Δ 4 of the 1st～the 4th glassy layer 1～4 and diameter a～d were to be benchmark with clad 7 in refractive index curve shown in Figure 10, determined according to the mean value of flat in each layer 1～4 and vertical component.

Wherein index α, the diameter a～d of refractive index profile shape determines by following in the refractive indices 1～Δ 4 of optical fiber, expression the 1st glassy layer 1.Just about optical fiber that refractive index curve shown in Figure 10 is arranged refractive indices 1～Δ 4, index α, diameter a～d as parameter, the simulation that these values are changed.Refractive indices 1～Δ 4, index α, diameter a～d are changed, find the solution simultaneously along in the whole wavelength band territory of 1460～1625nm of S-wave band, C-wave band and L-wave band, dispersion value has been represented the result of the wavelength 1550nm of optimum solution at refractive indices 1～Δ 4, index α, the diameter a～d of maximum difference the best when 4 (ps/nm/km) are following of 2～8ps/nm/km, dispersion value in the table 3.

Table 3

	??Δ1	????Δ2	???Δ3	???Δ4	???α	??????????????a∶b∶c∶d
										??a	????b	????c	????d
						??#3-1	??0.47	???-0.4	??-0.05					???0.4	???8	??1	????1.7	????2.1	????2.6
??#3-2	??0.48	???-0.45	??-0.1	???0.4	???8					??1	????1.5	????2.1	????2.5
						??#3-3	??0.50	???-0.45	??-0.1					???0.35	???8	??1	????1.5	????2.1	????2.5
??#3-4	??0.48	???-0.4	??-0.05	???0.4	???6					??1	????1.6	????2.1	????2.5
						??#3-5	??0.52	???-0.4	??-0.1					???0.4	???4	??1	????1.5	????2.1	????2.5

When determining this optimum solution, change the dispersion inclination (ps/nm that the subordinate parameter that changes adopts the dispersion (ps/nm/km) of wavelength 1550nm, identical wavelength with refractive indices 1～Δ 4, index α, diameter a～d ²/ km), actual effect core cross-sectional area Aeff (the μ m of identical wavelength ²), the cable cut-off wavelength λ of length 22m _c(nm), the diffusing wavelength X of zero ₀(nm), the bending loses (dB/m) of the diameter 20mm of identical wavelength and core diameter (μ m).The value of each the subordinate parameter shown in the formation table 3 as a result the time is shown in table 4.When this simulates, be shown in Figure 11 with respect to the dispersing characteristic of wavelength about the description of the #3-1 shown in the table 3,4～#3-5 optical fiber.

Table 4

	Disperse	Disperse to tilt	??Aeff	???λc	???λ 0	Bending loses	The core diameter
								??#3-1	???6.12	????0.0016	???46	??＜1550	???1334	????3.0	????19.3
??#3-2	???7.56	????0.0095	???45	??＜1550	???1328	????2.0	????18.8
								??#3-3	???4.41	????0.0007	???44	??＜1550	???1355	????2.0	????18.7
??#3-4	???7.28	????0.0096	???47	??＜1550	???1333	????1.0	????19.7
								??#3-5	???7.74	????0.0096	???43	??＜1550	???1335	????3.0	????18.9

From the analog result shown in the table 4 as can be seen, all more than 2 (ps/nm/km), disperseing to tilt is 0.010 (ps/nm for setting refractive indices 1～Δ 4 as shown in table 3, index α, diameter a～d, the dispersion value of the wavelength 1550nm of optical fiber ²/ km) following on the occasion of, cable cut-off wavelength λ _cBelow 1550 (nm), the bending loses of diameter 20mm is 5 (dB/m).

In this external table 4 as can be seen the wavelength X because zero is loose ₀Below 1360nm, the optical fiber of embodiment 3 expands transport tape territory that can Raman's amplification to the S-wave band.Optical fiber shown in the table 4 is arranged again because actual effect core cross-sectional area Aeff is 40 (μ m ²) more than, carry out WDM transmission in wavelength band territory with this actual effect core cross-sectional area Aeff, can look to suppressing the impairment that causes because of non-linear phenomena.

The words of considering Figure 11 on the other hand as can be seen, is below 2 (ps/nm/km) by the maximum difference of setting the optical fiber dispersion value of refractive indices 1～Δ 4, index α, diameter a～d shown in the table 3 in the whole wavelength band territory of 1460～1625nm, in other words, the whole wavelength band territory along 1460～1625nm disperses to tilt very little.The optical fiber of embodiment 3 is because (dispersion value that beyond the #3-3 is 1370～1650nm) wavelength region may is 2～8 (ps/nm/km) at 1400～1650nm in addition, so in the so-called wide band of the wide 250nm of wavelength (#3-3 beyond wavelength wide be 280nm), the realization wavelength dispersion is smooth, can look to suppressing four light waves and mix.

Wherein Figure 12 adds that to Figure 11 (1360～1525nm), being illustrated in Raman's excitation band territory dispersion value simultaneously is the dispersing characteristic of the optical fiber of 2～8 (ps/nm/km) for Raman's excitation band territory about the wavelength band territory of 1460～1625nm.As can be seen from Figure 12, the diffusing wavelength X of the optical fiber zero of embodiment 3 ₀Compare in shortwave one side with Raman's excitation band territory, as existing situation, the diffusing wavelength of zero is not overlapping with Raman's excitation band territory, therefore the optical fiber of embodiment 3 can remove can not Raman's amplification at the S-wave band restriction, can Raman's amplification in the whole wavelength band territory of 1460～1625nm of S-wave band, C-wave band, L-wave band.

The optical fiber of embodiment 3 can have the 1st～the 4th glassy layer 1～4 at least, also can be more than 5 layers.

Analog result shown in the table 3,4 is the basis, has actually studied 3 kinds of optical fiber, the dispersion of having measured dispersion value (ps/nm/km) about the various optical fiber 1460nm that study, 1550nm, 1620nm, the 1550nm (ps/nm that tilts ²/ km), actual effect core cross-sectional area Aeff (the μ m of identical wavelength ²), cable cut-off wavelength λ _c(nm), the diffusing wavelength X of zero ₀(nm), the bending loses (dB/m) of the diameter 20mm of 1550nm.It the results are shown in table 5.The dispersion wavelength characteristic that table 13 expression is measured 3 kinds of optical fiber that study.

Table 5

	Disperse			Disperse to tilt	???Aeff	??λc	??λ 0	Bending loses
									???1460nm	???1550nm	???1625nm	??1550nm	??1550nm	??22m	??1550nm
	??#5-1	????5.32	????7.02	????7.07	????0.0087	????45		??933								??1340	????5
??#5-2							????4.32		????5.75	????5.51	????0.0054	????45	??925	??1352	????8
	??#5-3	????5.81	????7.71	????7.95	????0.0100	????45		??945								??1335	????2

From table 5 and result shown in Figure 13 as can be seen, the optical fiber that refractive indices 1～Δ 4, index α, diameter a～d is set at the #5-1～#5-3 of above-mentioned value manufacturing all is 2～8 (ps/nm/km) at the whole wavelength band territory of 1460～1625nm of S-wave band, C-wave band, L-wave band dispersion value, disperses to tilt to be to the maximum 0.01 (ps/nm ²/ km), also very little, the maximum difference of dispersion value is below 3 (ps/nm/km).(dispersion value in 1460～1530nm) band territories is all more than 2 (ps/nm/km) at the S-wave band in each optical fiber of embodiment 3 like this.Therefore the optical fiber of the #5-1～#5-3 interference that can avoid four light waves to mix as can be seen.As shown in table 5 in addition, the optical fiber cable cut-off wavelength λ of #5-1～#5-3 _cAll below 950nm, actual effect core cross-sectional area Aeff is at 40 (μ m ²) more than.Because actual effect core cross-sectional area Aeff is at 40 (μ m ²) more than, so can suppress the impairment that non-linear phenomena causes.

But refractive indices 1～Δ 4, index α, the diameter a～d of embodiment 3 regulations are the values on analog basis, disperse to wait also inconsistent with the value shown in the table 4 sometimes in the actual optical fiber of making.For example bending loses (dB/m) is below 5 (dB/m) with Simulation result, and the numeric ratio of the optical fiber of making simulation big wishes refractive indices 1～Δ 4, index α, diameter a～d are set under the situation of above-mentioned value below 10dB/m.

3 kinds of optical fiber that study have been measured flashlight transmission loss (dB/km) and the polarized wave form of mode field diameter MFD (μ m), 1550nm in the flashlight of 1550nm and disperseed PMD (ps/  km).It the results are shown in the table 6.

Table 6

	????MFD	Transmission loss	???PMI
				??1550nm	????1550nm
	#5-1	????7.5				????0.218	??0.029
#5-2			????7.5	????0.254	??0.043
	#5-3	????7.5				????0.207	??0.049

As shown in table 6, the mode field diameter of optical fiber that refractive indices 1～Δ 4, index α, diameter a～d is set at the #5-1～#5-3 of above-mentioned value is that 7.5 μ m, transmission loss are that 0.207～0.254 (dB/km), polarized wave form are separated into below 0.029～0.049 (the ps/  km), all be extraordinary scope, particularly have the polarized wave form and be dispersed in the following characteristics of 0.1 (ps/  km).The optical fiber of #5-1～#5-3 can disperse the polarized wave form to limit very for a short time, and the transmission quality that can suppress in the WDM transmission worsens.The optical fiber zero of the #5-1～#5-3 wavelength X of loosing in addition ₀All below 1360nm.Therefore optical fiber promptly uses Raman's amplification that the problem of interfering with exciting light does not take place yet, and can expand the transport tape territory of Raman's amplification to the S-wave band.

From the such result of #5-1～#5-3 as can be seen, the optical fiber of embodiment 3 disperses to tilt to realize to disperse the wavelength planarization by reducing, the accumulation that can be suppressed at long wave one side disperses, avoiding four light waves to mix the band territory of generation to the expansion of shortwave direction, the whole wavelength band territory that this result expands the band territory that can transmit 1460～1625nm of S-wave band, C-wave band, L-wave band to.

Example 1 to the optical communication system of embodiments of the invention 3 describes below.Figure 14 is the diagram of structure of optical communication system of the example 1 of expression embodiments of the invention 3.The optical communication system 310 of the example 1 of embodiment 3 is to make optical transmission pathway with the optical fiber of embodiment 3, is provided with decentralized Raman amplifier 311, makes the S-wave band, concentrated light amplifier 317,318, the dispersion compensation apparatus 320 of the flashlight amplification at least one wavelength band territory in the C-wave band, L-wave band.

The optical fiber 301 of optical transmission pathway is in the flashlight transmission direction, a side is provided with demultiplexer 315 and multiplexer 316 every certain intervals in the upstream of profile Raman amplifier 311, in the downstream of profile Raman amplifier 311 side, be provided with dispersion compensation apparatus 320.

Profile Raman amplifier 311 has the set demultiplexer 314 of optical fiber 301 of the exciting light source 312 that excites S-band signal light and optical transmission pathway.313 pairs of demultiplexers of exciting light source 312 usefulness optical fiber 314 connect, and the rear of the flashlight of usefulness S-wave band is to excitation.

Concentrated light amplifier the 317, the 318th, be separately positioned on 2 with demultiplexer 315 and optical fiber 319 that multiplexer 316 is connected on germanium optical fiber amplifier (EDFA), each concentrated light amplifier 317 is for being used for C-band signal light, and concentrated amplifier 318 is for being used for L-band signal light.

Dispersion compensation apparatus 320 has 3 dispersion-compensating fibers 323,325,327 that are connected between demultiplexer 321, multiplexer 322, demultiplexer 321 and the multiplexer 322.3 dispersion-compensating fibers 323,325,327 are respectively the dispersion-compensating fiber that S-wave band, C-wave band, L-wave band are used, and the light amplifier 324,326,328 of compensating signal light loss is arranged in each band setting.

The optical communication system 310 of the example 1 of embodiment 3 is used profile Raman amplifier 311 as the optical fiber of optical transmission pathway use embodiment 3.Therefore optical communication system 310 utilizes the maximum power that makes input optical fibre 301 to reduce, and can be suppressed at the signal distortion that the non-linear phenomena that generates in the optical fiber 301 causes reliably.

Wherein Raman's amplifier has the concentrated amplifier except above-mentioned profile, uses in the WDM transmission under the concentrated amplifier situation, can not ignore the influence of the non-linear phenomena that produces in the optical fiber.The optical communication system 310 of this example 1 uses the actual effect core cross-sectional area Aeff of wavelength 1550nm at 40 (μ m ²) above optical fiber.Therefore optical communication system 310 is promptly used under the situation of concentrated Raman amplifier, by carrying out WDM transmission, the signal distortion that can avoid non-linear phenomena to cause.

Example 2 to the optical communication system of embodiments of the invention 3 describes below.Figure 15 is the diagram of structure of optical communication system of the example 2 of expression embodiments of the invention 3.The optical communication system 330 of the example 2 of embodiment 3 is to make the flashlight rear of 312 pairs of C-wave bands of exciting light source and S-wave band to excitation in the optical communication system 310 of example 1.

Therefore optical communication system 330 is compared with the optical communication system 310 of example 1, there is no need to be provided for the concentrated light amplifier 17 of C-band signal light because as long as the L-wave band with concentrated light amplifier 18 just can, can reduce component count.

By using the optical fiber of present embodiment 3, disperse owing to can reduce accumulation, for example under the situation about using with transmission speed 10Gbit/s, the dispersion compensation apparatus 20 shown in Figure 14, Figure 15 of expression example 1 and example 2 structures, not needing.Therefore as shown in figure 16, can reduce the parts of structure.Its advantage also has in addition: even surpass under the situation of high-speed transfer of 40Gbit/s, the grade differential that uses the optical fiber of this embodiment 3 also can disperse, design use single-mode optical fiber is enough in the dispersion-compensating fiber in the dispersion compensation apparatus so be placed on, and there is no need to be provided with new dispersion-compensating fiber.Embodiment 4

Below with figure explanation embodiments of the invention 4.The refractive index distribution curve of (a) expression optical fiber embodiment 4 of the present invention of Figure 17, (b) of this figure represents this profile of optic fibre structure.

Refractive Index Profile o curve as embodiment 4 can have various refractive index curve, and structure is more simple in embodiment 4, and the design of refractive index structures, control are easily adopted the refractive index curve shown in (a) of Figure 17.

The optical fiber of embodiment 4 covers core 11 with clad 7, above-mentioned core 11 is made of the glassy layer of forming different multilayers (4 layers) between adjacent (the 1st glassy layer the 1, the 2nd glassy layer the 2, the 3rd glassy layer the 3, the 4th glassy layer 4) at least, and these glassy layers become concentric garden shape.Clad with respect to above-mentioned 4 layers of glassy layer be as the refraction index profile benchmark the layer, be benchmark with it.

The largest refractive index of the 1st glassy layer 1 of the optical fiber innermost layer of embodiment 4 and from the inboard largest refractive index of the 3rd several the 3rd layer glassy layers 3 is than the refractive index height of clad 7, the minimum refractive index of the 2nd several the 2nd layer glassy layers 2 is lower than the refractive index of clad 7 from the inboard.The refractive index profile shape of the 1st glassy layer 1 is the α power.

Optical fiber the 1st glassy layer 1 of embodiment 4 for the refringence of clad 7 be defined as/when Δ the 1, the 2nd glassy layer 2 was defined as Δ the 2, the 3rd glassy layer 3 and is defined as Δ 3 for the refringence of clad 7 for the refringence of clad 7, the pass was Δ 1＞Δ 3＞Δ 2.

The diameter that the diameter that the diameter of the 1st glassy layer is defined as a, the 2nd glassy layer is defined as b, the 3rd glassy layer is defined as c.

In the refractive index curve of embodiment 4, there is no particular limitation for the value of the value of each refractive indices 1, Δ 2, Δ 3 and each diameter a, b, c, wishes to be suitable for these values at following scope embodiment 4.

Just refractive indices 1 is more than 0.3%, below 0.8%, refractive indices 2 is more than-0.6% ,-below 0.05%, refractive indices 3 is more than 0.05%, below 0.4%.Diameter is a benchmark than with diameter a, scope dictates be diameter than b/a more than 1.5, below 2.2, diameter than c/a more than 2.2, below 3.5.

The dispersion value of the fiber optic wavelength 1550nm of embodiment 4 is more than the 4ps/nm/km, and wavelength 1460nm～1625nm has at least the dispersion of the wavelength band of part setting to tilt to be 0.05ps/nm ²/ km following on the occasion of (being preferably 0.025ps/nm ²/ km following on the occasion of).

The cut-off wavelength of the fiber lengths 2m of embodiment 4 is at (preferably below 1450nm) below the 1550nm, and zero is loose wavelength at (preferably below 1400nm) below the 1450nm, and the transmission loss of wavelength 1385nm is below 1.5dB/km.

The wavelength actual effect core cross-sectional area that fiber optic wavelength 1460nm～1625nm of embodiment 4 has at least a part to set is 40 μ m ²～60 μ m ²(be preferably 45 μ m ²Below), the bending loses of the diameter 20mm of wavelength 1550nm is below the 5dB/m, the polarized wave form of wavelength 1550 is separated into below the 0.08ps/  km.

The inventor determines the structure of embodiment 4 substantially at first in order mainly to be to carry out wavelength segmentation multiplexing in C-wave band band territory, has carried out following research.

(flashlight of wavelength 1530nm～1565nm) carries out under Raman's amplification situation to C-wave band band territory, the excitation of the minimal wave length (1530nm) of general C-wave band is suitable for wavelength 1420nm～1430nm, and the long wavelength's (1565nm) of general C-wave band excitation is suitable for wavelength 1455nm～1465nm.Wish that excitation light power loss deviation (maximum of loss value and minimum value poor) in each wavelength region may is in ± 10% this moment.

Just the loss deviation in the wavelength region may of each exciting light source of optical fiber is ± 10% with interior, and for the amplification that WDM flashlight integral body is obtained stipulating, it is just passable only to adjust exciting light source intensity.In contrast, the loss deviation greater than ± 10% situation under, the intensity of adjusting exciting light source is not only in above-mentioned adjustment, sometimes the wavelength interval of a plurality of exciting light sources also must be adjusted, exciting light source not only has to preestablish towards the periodical angle, because the kind of exciting light source increases, the problem of cost also appears.

The relation of the loss deviation of the transmission loss of the characteristic curve of Figure 18 (a) expression wavelength 1385nm (the loss peak value that the hydroxyl concentration in the optical fiber causes) and 1420nm～1430nm, the characteristic curve b of this figure represents the relation of the loss deviation of the transmission loss of wavelength 1385nm and 1455nm～1465nm.Loss when in such cases, the loss deviation is respectively the wavelength change 10nm in wavelength band territory changes.

Can clearly be seen that from characteristic curve a, the b of Figure 18, consider the dependence of transmission loss and wavelength, for the transmission loss Deviation Control of wavelength 1420nm～1430nm and 1455nm～1465nm in ± 10%, just in this case, loss when making wavelength change 10nm changes in ± 10%, can be controlled at below the 1.5dB/km in the transmission loss of wavelength 1385nm.

(a) expression of Figure 19 is controlled at the transmission loss of wavelength 1385nm under the following situation of 1.5dB/km, the dependence of fiber loss and wavelength, under the situation of transmission loss of (b) expression wavelength 1385nm of Figure 19 greater than 1.5dB/km, the dependence of fiber loss and wavelength.

Figure 20 is illustrated in and makes in the optical fiber shown in Figure 17 on the other hand, from the 1st glassy layer 1 to the 3rd glassy layer, 3 usefulness vapour deposition processes (VAD method) synthetic after, the mother metal outer surface of clear glassization with fluoric acid amount of pruning and the optical fiber that obtains in this way relation in the transmission loss of wavelength 1385nm.Therefore by surface etching is removed more than the 1mm, the transmission loss of wavelength 1385nm is reduced to below the 1.5dB/km.

As mentioned above, the optical fiber of embodiment 4 utilizes to be removed above-mentioned surface etching more than the 1mm, and the transmission loss of wavelength 1385nm is reduced to below the 1.5dB/km.Therefore the optical fiber of embodiment 4 uses the fiber loss deviation in ± 10% in the transmission in excitation wavelength band territory.

The amplification coefficient of Raman's amplification is owing to the actual effect core cross-sectional area with optical fiber is inversely proportional to, and actual effect core cross-sectional area is excessive, causes the efficient of Raman's amplifier to reduce.At least the actual effect core cross-sectional area that makes a part set the wavelength band territory among the fiber optic wavelength 1460nm～1625nm of present embodiment is 60 μ m ²Below.Therefore also can suppress the reduction of Raman's amplifier efficient when the optical fiber of embodiment 4 adopts a kind of Raman's amplification of profile and constant type.

The actual effect core cross-sectional area of optical fiber is too small, causes the flashlight deterioration to become greatly owing to modulate (SPM) mutually because of self-alignment with the non-linear phenomena that mutual position is modulated (XPM) mutually, and the optical fiber of embodiment 4 makes actual effect core cross-sectional area at 40 μ m ²More than therefore the optical fiber of embodiment 4 can suppress that self-alignment is modulated mutually and the position flashlight deterioration that causes of modulation mutually mutually.

When the C-of carrying out band transmission was arranged again, the words that the dispersion value of wavelength 1550nm is very little can cause the interference that four light waves mix.The optical fiber of embodiment 4 makes the dispersion value of wavelength 1550nm more than 4ps/nm/km.Therefore the optical fiber of embodiment 4 can suppress the flashlight waveform distortion that interference that four light waves mix causes.

In order to carry out the single-mode action with the C-band transmission, the optical fiber of embodiment 4 makes cut-off wavelength below 1550nm.Therefore the optical fiber of embodiment 4 can carry out the single-mode action with the C-band transmission.

Cut-off wavelength is the smaller the better, considers the technology such as fiber optic applications Raman's amplification that make embodiment 4, preferably makes cut-off wavelength below 1450nm.

The dispersion wavelength gradient (disperseing to tilt) of carrying out the multiplex optical fiber of wavelength segmentation is big, and wavelength respectively disperses grade differential (dispersion difference) to become big, and communication brings harm to high-capacity and high-speed.In contrast, the dispersion wavelength gradient of the multiplex optical fiber of wavelength segmentation can be reduced, the grade differential of each wavelength dispersion might be suppressed.

The dispersion that the optical fiber of embodiment 4 is set in the wavelength band at least a portion of wavelength 1460nm～1625nm tilts to be 0.05ps/nm ²/ km following on the occasion of.From then on this optical fiber disperse the relation of tilting value and above-mentioned dispersion value to consider, makes zero loose wavelength below 1460nm.This optical fiber can further suppress the dispersion grade differential of each wavelength, can further suppress to disperse the wave distortion that causes.

In embodiment 4, preferred optical fiber is that the dispersion that at least a portion of wavelength 1460nm～1625nm is set in the wavelength band tilts to be 0.025ps/nm ²/ km following on the occasion of.From then on this optical fiber disperse the relation of tilting value and above-mentioned dispersion value to consider, makes zero loose wavelength below 1400nm.This optical fiber can further suppress the dispersion grade differential of each wavelength, can further suppress to disperse the wave distortion that causes.

The bending loses of optical fiber is big, makes under the situation of optical fiber mode blocking use etc. and can produce harm.The optical fiber of embodiment 4 makes the bending loses of diameter 20mm of wavelength 1550nm below 5dB/m.Therefore, also can suppress to lose the problem of increase even the optical fiber of embodiment 4 for example is rolled into behind the spool modularization and is used for optical transmission pathway.Bending loses is the smaller the better, and bending loses is more little to obtain high confidence level more.

It is big that the polarized wave form is disperseed, and the difference of particularly polarization direction causes during high-speed transfer flashlight time of delay becomes big, and transmission has bad influence to signal.The optical fiber of embodiment 4 is dispersed in below the 0.08ps/  km polarized wave form of wavelength 1550nm.Therefore the influence of the optical fiber polarisation waveshape of embodiment 4 dispersion is also few, is applicable to Raman's amplification technology.

The inventor is undertaken by following mode the optimization of the refractive index curve of optical fiber with said structure, and the optical fibre refractivity curve of embodiment 4 is determined by above-mentioned.

Just for refractive index curve shown in Figure 17, the relation of each refractive indices 1, Δ 2, Δ 3 and optic fibre characteristic is studied, and the refractive indices of finding to make the 1st glassy layer 11 is greater than 0.8%, and above-mentioned dispersion tilts to be 0.050ps/nm ²/ km following on the occasion of with make actual effect core cross-sectional area at 40 μ m ²More than be difficult to realize simultaneously.Refractive indices 1 to 0.3% is little in addition, and it is big that bending loses becomes, more than 5dB/m.So the scope of refractive indices 1 is more than 0.3%, below 0.8%.

Refractive indices 1 has been obtained the constant alpha of disperseing when enlarging actual effect core cross-sectional area to tilt not increase in the scope more than 0.3%, below 0.8%, it is suitable more than 4 to judge.

The refractive indices 2 of finding the 2nd glassy layer 2 is greater than-0.05%, and above-mentioned dispersion is tilted greater than 0.050ps/nm ²/ km, refractive indices 2 to-0.6% is little, and actual effect core cross-sectional area is than 40 μ m ²Little.So the scope of refractive indices 2 is more than-0.6% ,-below 0.05%.

The diameter b that makes the 2nd glassy layer 2 disperses to tilt greater than 0.050ps/nm than 2.2 times also big of the diameter a of the 1st glassy layer 1 ²/ km, the diameter b that makes the 2nd glassy layer 2 is than 1.5 times also little of the diameter a of the 1st glassy layer 1, and actual effect core cross-sectional area is than 40 μ m ²Little.So that the scope of b/a more than 1.5, below 2.2.

Discovery makes the refractive indices 3 of the 3rd glassy layer 3 greater than 0.4%, and above-mentioned cut-off wavelength is greater than 1550nm, and refractive indices 3 is less than 0.05%, and above-mentioned dispersion is tilted greater than 0.050ps/nm ²/ km.So the scope of refractive indices 3 is more than 0.05%, below 0.4%.

The diameter c that makes the 3rd glassy layer 3 is than 3.5 times also big of the diameter a of the 1st glassy layer 1, and above-mentioned cut-off wavelength is greater than 1550nm, and the diameter c that makes the 3rd glassy layer 3 disperses to tilt greater than 0.050ps/nm than 2.2 times also little of the diameter a of the 1st glassy layer 1 ²/ km.So that the scope of c/a more than 2.2, below 3.5.

Embodiment 4 is to utilize to determine above-mentioned refractive index curve owing to be the optical fiber of above-mentioned demonstration excellent results, can realize that the C-wave band uses the multiplex optical fiber of wavelength segmentation of Raman's amplification technology.

The optical communication system of making optical transmission pathway of the optical fiber of embodiment 4 is to realize good optical communication system, can carry out high-quality wavelength segmentation multiplexing with Raman's amplifier etc.

Example to embodiment 4 describes below.As the example of embodiment 4, actual fabrication the optical fiber shown in the table 7.

Table 7

	Disperse			Disperse to tilt	??MFD	??Aeff	Transmission loss		????λc	????λ 0	????PMD	Bending loses
													???1460nm	???1550nm	???1620nm	????1550nm	???1550nm	???1550nm	????1385nm	????1550nm	????1550nm
	??#7-1	????---	????4.8	????---	????0.0292	????7.8	????45.2	????1.185				????0.209										????1159	????1412	????0.045	????0.212
??#7-2									????---	????5.6	????---		????0.0293	????8.0	????47.8	????0.893	????0.207	????1446	????1393	????0.048	????0.021
	??#7-3	????---	????4.6	????---	????0.0444	????8.5	????54.5	????0.658				????0.202										????1070	????1448	????0.030	????4.300
??#7-4									????---	????7.7	????---		????0.0226	????7.6	????43.8	????1.457	????0.211	????1101	????1353	????0.053	????3.210
	??#7-5	????---	????8.8	????---	????0.0325	????7.7	????44.4	????0.303				????0.193										????1222	????1350	????0.057	????0.041
??#7-6									????2.0	????4.8	????6.6		????0.0252	????7.8	????45.2	????1.185	????0.209	????1159	????1402	????0.045	????0.212
	??#7-7	????2.2	????4.2	????5.0	????0.0156	????7.5	????42.6	????1.411				????0.206										????1156	????1396	????0.026	????4.018
??#7-8									????2.7	????4.9	????6.1		????0.0200	????7.6	????44.5	????0.983	????0.211	????1273	????1387	????0.027	????0.914

The unit of the dispersion value of table 7 is ps/nm/km, and the unit that disperses to tilt is ps/nm ²/ km, each value be under each project shown in the value of wavelength.

MFD represents that mode field diameter, Aeff represent actual effect core cross-sectional area in addition, loses to be transmission loss, and bending loses 20 φ represent the bending loses of diameter phi 20mm, the value of the wavelength shown under these projects of each value representation.The unit of MFD is μ m, and the unit of transmission loss is dB/km, and the unit of bending loses is dB/m, and the unit of Aeff is μ m ²

λ _cBe cut-off wavelength, λ ₀Be the diffusing wavelength of zero, their unit is nm.PMD represents the dispersion of polarized wave form, and its unit is ps/  km.

The characteristic curve a of Figure 21 represents that optical fiber #7-8 that table 7 studies is to disperseing the dependence of wavelength.Characteristic curve b, the c of this figure represents that respectively the dispersion value of wavelength 550nm is 4.9ps/nm/km, disperses to tilt to be 0.045ps/nm ²Optical fiber and the 0.060ps/nm of/km (identical) with the value of the #7-8 of table 7 ²The dispersion of the optical fiber of/km and the dependence of wavelength.

Shown in the characteristic curve a of Figure 21, the dispersiveness of the optical fiber that studies (#7-8) is not only C-wave band band territory (wavelength 1530nm～1565nm), comprise S-wave band band territory (wavelength 1460nm～1530nm), L-wave band (in the wideer scope of wavelength 1565nm～1620nm), dispersion value is+2～+ 8ps/nm/km.

If setting the dispersion in a part of wavelength band territory at least more than 4ps/nm/km, among wavelength 1460nm～1625nm, the dispersion value that makes wavelength 1550nm like this tilts to be 0.025ps/nm ²/ km following on the occasion of, in the wide scope from the S-band extension to the L-wave band, dispersion value can be for+2～+ 8ps/nm/km.Therefore the optical fiber (#7-8) that studies can suppress the mixing of four light waves in this wave-length coverage, realizes high-quality wavelength segmentation multiplexing.

The dispersion value of fiber optic wavelength 1550nm of characteristic curve C with Figure 21 is identical with the optical fiber that studies (#7-8), owing to disperse to tilt to be 0.060ps/nm ²/ km is about 3 times that the dispersion of the optical fiber (#7-8) that studies is tilted, and the absolute value of the dispersion value of S-wave band is too small, and the problem that four light waves mix takes place.This optical fiber produces because of disperseing to cause the problem of light distortion because the absolute value that disperses at the L-wave band is big.

Optical fiber with characteristic curve b of Figure 21 disperses to tilt to be 0.045ps/nm ²/ km, bigger than the optical fiber that studies (#7-8), the dispersion value of L-wave band becomes greatly a little, and still, the probability height that four light waves mix takes place in this zone in the absolute value of the dispersion value of S-wave band below 2ps/nm/km.But the optical fiber with characteristic curve b of Figure 21 is compared with the characteristic curve C shown in the same figure, has good dispersing characteristic.

The optical fiber (#7-6, #7-7, #7-8) that (a)～(c) expression table 7 of Figure 22 studies is to disperseing the dependence of wavelength.#7-6, #7-7 to study optical fiber also the same with #7-8, be in scope from the S-wave band to the L-wide waveband, make dispersion value be+2～+ 8ps/nm/km, can suppress the signal distortion that mixes and disperse to cause because of four light waves, can realize high-quality wavelength segmentation multiplexing.

This embodiment 4 is not limited to above-mentioned each example, can adopt various execution modes.For example in the above embodiments 4, core 11 has the 3-tier architecture of the 1st glassy layer the 1, the 2nd glassy layer the 2, the 3rd glassy layer 3, and optical fiber of the present invention also can have the core more than 4 layers.

In optical fiber of the present invention, the bending loses of optimal wavelength 1550nm, dispersion value, transmission loss still, also can depart from this scope slightly in the scope shown in the foregoing description 4.

Claims (60)

1. optical fiber, it is characterized by: the dispersion absolute value in the whole zone of wavelength from 1430nm to 1625nm is more than the 0.5ps/nm/km, below the 9ps/nm/km; The dispersion inclination absolute value of wavelength 1550nm is at 0.04ps/nm ²Below/the km; The mode field diameter of wavelength 1550nm is below the 7 μ m; Cable cut-off wavelength is less than 1430nm.

2. optical fiber as claimed in claim 1 is characterized by: the dispersion inclination absolute value of wavelength 1550nm is 0.03ps/nm ²Below/the km.

3. optical fiber as claimed in claim 2 is characterized by: the dispersion absolute value in the whole zone of wavelength from 1360nm to 1625nm is more than the 0.5ps/nm/km, below the 9ps/nm/km; Cable cut-off wavelength is below the 1360nm.

4. optical fiber as claimed in claim 1 is characterized by: the transmission loss of wavelength 1550nm is below the 0.25dB/km.

5. optical fiber as claimed in claim 1 is characterized by: the transmission loss of wavelength 1385nm is below the 1.0dB/km.

6. optical fiber as claimed in claim 1 is characterized by: the loss of wavelength 1385nm increases to below 10% under the hydrogen environment.

7. optical fiber as claimed in claim 1 is characterized by: the polarized wave form of wavelength 1550nm is separated into below the 0.5ps/  km.

8. optical fiber as claimed in claim 1 is characterized by: the polarized wave form of wavelength 1550nm is separated into below the 0.2ps/  km.

9. optical fiber as claimed in claim 1 is characterized by: the periphery of mandrel layers covers clad, and above-mentioned mandrel layers has the 1st glassy layer that forms at fiber optic hub and the 2nd glassy layer that covers this 1st glassy layer periphery at least; Above-mentioned the 1st glassy layer is that the refringence of benchmark is more than 0.6%, below 1.6% with above-mentioned clad; Above-mentioned the 2nd glassy layer is that the refringence of benchmark is a negative value with above-mentioned clad.

10. optical fiber as claimed in claim 9, it is characterized by: each layer made with quartz, and the 1st glassy layer will add germanium at least, and the 2nd glassy layer will add fluorine at least.

11. optical fiber as claimed in claim 10 is characterized by: each layer made with quartz, the 1st glassy layer will add germanium and fluorine at least, and the 2nd glassy layer will add fluorine at least.

12. optical fiber as claimed in claim 11 is characterized by: the amount that the amount of the 1st glassy layer interpolation fluorine and the 2nd glassy layer add fluorine much at one.

13. optical fiber as claimed in claim 9 is characterized by: the 1st glassy layer and the 2nd glassy layer are synthetic simultaneously.

14. optical fiber as claimed in claim 13 is characterized by: metalclad zone is since the zone more than 2 times of border to the 2 glassy layer diameters of the 2nd glassy layer; The 1st glassy layer and the 2nd glassy layer are synthetic simultaneously.

15. an optical transmission pathway is characterized by: in the optical fiber of claim 1, each is connected more than 1 with having the negative optical fiber that disperses to have the optical fiber that is just disperseing.

16. optical transmission pathway as claimed in claim 15 is characterized by: the average dispersion value of the optical transmission pathway of the wavelength that wavelength is set in from 1460nm to the 1625nm scope or the wavelength region may of setting or whole wavelength region may is almost nil.

17. optical transmission pathway as claimed in claim 16 is characterized by: optical fiber sends a side from flashlight and links reception one side, and many vertically are connected to form; The optical fiber of mode field diameter maximum is placed on the position except that the most close flashlight receives a side position in the above-mentioned multifiber.

18. optical transmission pathway as claimed in claim 16 is characterized by: the wavelength region may that wavelength is set in from 1460nm to the 1625nm scope or the average dispersion value of whole wavelength region may for-more than the 1.0ps/nm/km, below the 1.0ps/nm/km.

19. optical transmission system as claimed in claim 18 is characterized by: the exciting light source that sends the exciting light of the signal optical source of flashlight and output and flashlight different wave length is connected on the optical transmission pathway of carrying light signal.

20. an optical fiber is characterized by: dispersion value D is 2≤D≤8 (ps/nm/km) in wavelength 1400～1700nm, and wavelength dispersion has 1 extreme value at least in above-mentioned wavelength band territory.

21. optical fiber as claimed in claim 20 is characterized by: the dispersion value D of wavelength 1310nm is-4≤D≤4 (ps/nm/km).

22. optical fiber as claimed in claim 20 is characterized by: cut-off wavelength is below the 1550nm.

23. optical fiber as claimed in claim 20 is characterized by: the bending loses under the diameter 20mm is below the 5dB/km when wavelength 1550nm.

24. optical fiber as claimed in claim 20 is characterized by: actual effect core cross-sectional area is 40 μ m when wavelength 1550nm ²More than.

25. optical fiber as claimed in claim 20 is characterized by: be below the 0.1ps/  km when polarized wave form is dispersed in wavelength 1550nm.

26. optical fiber as claimed in claim 20 is characterized by: dispersion value is-2≤D≤2 (ps/nm/km) when wavelength 1310nm.

27. optical fiber as claimed in claim 20 is characterized by: the diffusing wavelength of zero is below 1350.

28. optical fiber as claimed in claim 20, it is characterized by: between adjacent layer, have and form different multilayers, in these layers, there are a plurality of glassy layers clad inboard as the refraction index profile benchmark, at this optical fiber the 1st glassy layer of inboard formation, the order refringence of the 2nd glassy layer, the 3rd glassy layer, the 4th glassy layer and above-mentioned metalclad refractive index laterally is defined as Δ 1, Δ 2, Δ 3, Δ 4 respectively, metalclad refringence is defined as 0, has the relation of Δ 1＞Δ 3＞Δ 4＞0＞Δ 2.

29. optical fiber as claimed in claim 28, it is characterized by: the 1st glassy layer of inboard formation is 0.3～0.7% with respect to metalclad refractive indices 1, the constant alpha of expression refractive index profile shape is more than 4, external diameter is 124 μ m～126 μ m, and the diameter of the 1st glassy layer is 7.0～10.0 μ m.

30. optical fiber as claimed in claim 28, it is characterized by: the 2nd layer the 2nd glassy layer that forms from the inboard is-0.6～-0.2% with respect to metalclad refractive indices 2, the 2nd layer diameter is 1.2～1.8 times of the 1st layer of diameter, the 3rd layer the 3rd glassy layer that forms from the inboard is 0.25～0.5% with respect to metalclad refractive indices 3, the 3rd layer diameter is 1.8～2.2 times of the 1st layer of diameter, the 4th layer the 4th glassy layer that forms from the inboard is that the 0.05～0.2%, 4th layer diameter is 2.0～2.7 times of the 1st layer of diameter with respect to metalclad refractive indices 4.

31. optical fiber as claimed in claim 20, it is characterized by: between adjacent layer, have and form different multilayers, in these layers, there are a plurality of glassy layers clad inboard as the refraction index profile benchmark, at this optical fiber the 1st glassy layer of inboard formation, the order refringence of the 2nd glassy layer, the 3rd glassy layer, the 4th glassy layer, the 5th glassy layer and above-mentioned metalclad refractive index laterally is defined as Δ 1, Δ 2, Δ 3, Δ 4, Δ 5 respectively, metalclad refringence is defined as 0, has the relation of Δ 1＞Δ 4＞Δ 5＞0＞Δ 3＞Δ 2.

32. optical fiber as claimed in claim 31, it is characterized by: the 1st glassy layer of inboard formation is 0.3～0.7% with respect to metalclad refractive indices 1, the constant alpha of expression refractive index profile shape is more than 4, external diameter is 124 μ m～126 μ m, and the diameter of the 1st glassy layer is 6.5～10 μ m.

33. optical fiber as claimed in claim 31 is characterized by: the 2nd layer the 2nd glassy layer that forms from the inboard is 1.2～1.8 times of the 1st layer of diameter for the-0.6～-0.2%, 2nd layer diameter with respect to metalclad refractive indices 2; The 3rd layer the 3rd glassy layer that forms from the inboard is-0.15～-0.05% with respect to metalclad refractive indices 3, and the 3rd layer diameter is 1.8～2.2 times of the 1st layer of diameter; The 4th layer the 4th glassy layer that forms from the inboard is that the 0.25～0.65%, 4th layer diameter is 2.0～2.7 times of the 1st layer of diameter with respect to metalclad refractive indices 4; The 5th layer the 5th glassy layer that forms from the inboard is that the 0.05～0.50%, 5th layer diameter is 2.2～3.0 times of the 1st layer of diameter with respect to metalclad refractive indices 5.

34. an optical communication system is characterized by: include optical transmission pathway and S-wave band profile Raman amplifier with the optical fiber of claim 20 record.

35. an optical fiber is characterized by: the dispersion value in the full wavelength band territory of 1460～1625nm is 2≤D≤8 (ps/nm/km), and the maximum difference of dispersion value is below 4 (ps/nm/km).

36. optical fiber as claimed in claim 35 is characterized by: the maximum difference of dispersion value is below 2 (ps/nm/km).

37. optical fiber as claimed in claim 35 is characterized by: cable cut-off wavelength is below the 1550nm.

38. optical fiber as claimed in claim 35 is characterized by: the bending loses of the diameter 20mm of wavelength 1550nm is below the 10dB/m.

39. optical fiber as claimed in claim 35 is characterized by: set at least in wavelength 1460nm～1625nm in a part of wavelength band territory, actual effect core cross-sectional area is 40 μ m ²More than.

40. optical fiber as claimed in claim 35 is characterized by: the polarized wave form of wavelength 1550nm is dispersed in below the 0.1ps/  km.

41. optical fiber as claimed in claim 35, it is characterized by: adjacent layer each other refractive index different be that the 1st glassy layer～the 4th glassy layer forms concentric garden in order from the inboard at least, this glassy layer arranged outside of at least 4 layers has the metalclad ring plate type as the refraction index profile benchmark, the refringence of above-mentioned the 1st glassy layer～the 4th glassy layer and above-mentioned metalclad refractive index is defined as Δ 1～Δ 4 respectively, is set at the relation of Δ 1＞Δ 4＞Δ 3＞Δ 2 respectively.

42. optical fiber as claimed in claim 41, it is characterized by: the constant alpha of the expression refractive index profile shape of the 1st glassy layer is more than 4, refractive indices 1 with respect to the clad maximum is set at 0.3～0.7%, and the diameter a of the 1st glassy layer sets 0.05～0.1 times of clad diameter for this reason.

43. optical fiber as claimed in claim 41 is characterized by: above-mentioned the 2nd glassy layer is set at-0.6～-0.2% with respect to metalclad refractive indices 2, and external diameter b is set at 1.3～1.8 times of diameter a of above-mentioned the 1st glassy layer.

44. optical fiber as claimed in claim 41 is characterized by: above-mentioned the 3rd glassy layer is set at-0.2～-0.05% with respect to metalclad refractive indices 3, and external diameter c is set at 1.9～2.4 times of diameter a of above-mentioned the 1st glassy layer.

45. optical fiber as claimed in claim 41 is characterized by: above-mentioned the 4th glassy layer is set at 0.1～0.55% with respect to metalclad refractive indices 4, and outside diameter d is set at 2.6～2.8 times of diameter a of above-mentioned the 1st glassy layer.

46. optical communication system, it is characterized by: the optical fiber of claim 35 record as optical transmission pathway, is equipped with profile Raman amplifier and makes the concentrated light amplifier of the flashlight amplification at least 1 wavelength band territory in the S-wave band, C-wave band, L-wave band in the wavelength band territory of 1460～1625nm.

47. an optical fiber is characterized by: the dispersion value of wavelength 1550nm is more than the 4ps/nm/km, sets the dispersion in a part of wavelength band territory among wavelength 1460nm～1625nm at least and tilts to be 0.050ps/nm ²/ km following on the occasion of, the cut-off wavelength of the long 2m of optical fiber is below the 1550nm, the diffusing wavelength of zero is below the 1460nm, the transmission loss of wavelength 1385nm is below the 1.5dB/km.

48. optical fiber as claimed in claim 47 is characterized by: the dispersion of setting a part of wavelength band territory among wavelength 1460nm～1625nm at least tilts to be 0.025ps/nm ²/ km following on the occasion of.

49. optical fiber as claimed in claim 48, it is characterized by: form different compound glass layers mutually by adjacent layer and constitute, at least glassy layer haves three layers in metalclad inboard, the largest refractive index of the 1st glassy layer of the most inboard formation of this optical fiber and from the largest refractive index of inboard several the 3rd layer the 3rd glassy layer of optical fiber, than above-mentioned metalclad refractive index height, lower than above-mentioned metalclad refractive index from the minimum refractive index of the 2nd several the 2nd layer glassy layer of optical fiber inboard.

50. optical fiber as claimed in claim 49 is characterized by: the constant alpha of representing the 1st glassy layer refractive index profile shape is more than 4, and the 1st glassy layer is more than 0.3%, below 0.8% with respect to metalclad refractive indices 1; The 2nd glassy layer with respect to metalclad refractive indices 2 be more than-0.6% ,-below 0.05%; The 3rd glassy layer is more than 0.05%, below 0.4% with respect to metalclad refractive indices 3; Diameter a with the 1st glassy layer is a benchmark, and the diameter of the 2nd glassy layer is more than 1.5, below 2.2 than b/a; Diameter a with the 1st glassy layer is a benchmark, the diameter of the 3rd glassy layer than c/a more than 2.2, below 3.5.

51. optical fiber as claimed in claim 47 is characterized by: the actual effect core cross-sectional area of setting a part of wavelength band territory among wavelength 1460nm～1625nm at least is 40 μ m ²Above 60m ²Below.

52. optical fiber as claimed in claim 51 is characterized by: the actual effect core cross-sectional area of setting a part of wavelength band territory among wavelength 1460nm～1625nm at least is 40 μ m ²Above 45m ²Below.

53. optical fiber as claimed in claim 47 is characterized by: the bending loses of the diameter 20mm of wavelength 1550nm is below the 5dB/m.

54. optical fiber as claimed in claim 47 is characterized by: the cut-off wavelength of long 2m is below the 1450nm.

55. optical fiber as claimed in claim 47 is characterized by: the polarized wave form of wavelength 1550nm is separated into below the 0.08ps/  km.

56. optical fiber as claimed in claim 47 is characterized by: the diffusing wavelength of zero is below the 1400nm.

57. optical fiber as claimed in claim 47, it is characterized by: form different compound glass layers mutually by adjacent layer and constitute, at least glassy layer haves three layers in metalclad inboard, the largest refractive index of the 1st glassy layer of the most inboard formation of this optical fiber and from the largest refractive index of inboard several the 3rd layer the 3rd glassy layer of optical fiber, than above-mentioned metalclad refractive index height, lower than above-mentioned metalclad refractive index from the minimum refractive index of the 2nd several the 2nd layer glassy layer of optical fiber inboard.

58. optical fiber as claimed in claim 57 is characterized by: the constant alpha of representing the 1st glassy layer refractive index profile shape is more than 2, and the 1st glassy layer is more than 0.3%, below 0.8% with respect to metalclad refractive indices 1; The 2nd glassy layer with respect to metalclad refractive indices 2 be more than-0.6% ,-below 0.05%; The 3rd glassy layer is more than 0.05%, below 0.4% with respect to metalclad refractive indices 3; Diameter a with the 1st glassy layer is a benchmark, and the diameter of the 2nd glassy layer is more than 1.5, below 2.2 than b/a; Diameter a with the 1st glassy layer is a benchmark, the diameter of the 3rd glassy layer than c/a more than 2.2, below 3.5.

59. an optical communication system is characterized by: the optical fiber of claim 47 record is applicable to makes optical transmission pathway.

60. optical communication system as claimed in claim 59 is characterized by: connect the Raman amplifier in the optical transmission pathway.

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