JP2001296444A - Dispersion compensating optical fiber, optical transmission line and dispersion compensating module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dispersion compensating optical fiber capable of compensating wavelength dispersion and a dispersion slope of a non-zero dispersion shifted optical fiber by a short measure. SOLUTION: In an optical transmission system 1, an optical transmission line 30 is laid in a repeater section between a station 10 and a station 20. In the optical transmission line 30, a dispersion shifted optical fiber 31 is connected by welding to a dispersion compensating optical fiber 32. In the dispersion shifted optical fiber 31, wavelength dispersion DDSF is +2 ps/nm/km to +10 ps/nm/km, the dispersion slope SDSF is +0.04 ps/nm2/km to +0.12 ps/nm2/km and a transmission loss is nearly 0.20 dB/km at the wavelength of 1,550 nm. In the dispersion compensating optical fiber 32, wavelength dispersion DDCF is -40 ps/nm/km or below and the ratio (SDCF/DDCF) of wavelength dispersion DDCF to the dispersion slope SDCF is 0.005/nm or above at the wavelength of 1,550 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dispersion compensating optical fiber for compensating chromatic dispersion and dispersion slope of a dispersion-shifted optical fiber, an optical transmission line including the dispersion-shifted optical fiber and the dispersion-compensating optical fiber, and an optical transmission line including the same. The present invention relates to a dispersion compensating module in which a dispersion compensating optical fiber is wound into a coil and modularized.

[0002]

2. Description of the Related Art Wavelength division multiplexing (WDM)
n Multiplexing) In an optical transmission system that performs optical transmission, in order to further increase the speed and capacity of optical communication, the absolute value of the accumulated chromatic dispersion of the optical transmission line should be minimized in a wide signal light wavelength band. is important. In general, it is difficult to use an optical transmission line using only one type of optical fiber. Therefore, by constructing an optical transmission line by connecting a plurality of types of optical fibers, the accumulated chromatic dispersion of the optical transmission line over a wide band can be reduced. The absolute value is reduced.

For example, Japanese Unexamined Patent Publication No. 6-11620 discloses a standard single mode fiber (SMF) having a zero dispersion wavelength around 1.3 μm.
r) and a dispersion compensating fiber (DCF: Dispersion Compensating Fiber) for compensating chromatic dispersion at a wavelength of 1550 nm of this standard single mode optical fiber, and an optical transmission line configured by connecting these. A technique for reducing the absolute value of the accumulated chromatic dispersion in the 1.55 μm wavelength band is disclosed.

Further, US Pat. No. 5,838,867 discloses a non-zero dispersion shifted optical fiber (NZDSF: Non-Zero D) having a small positive chromatic dispersion at a wavelength of 1550 nm.
ispersion shift fiber) and a dispersion compensating optical fiber for compensating chromatic dispersion and dispersion slope at a wavelength of 1550 nm of the dispersion-shifted optical fiber, and a wavelength 1.55 of an optical transmission line formed by connecting these.
A technique for reducing the absolute value of the accumulated chromatic dispersion in the μm band is disclosed.

[0005] Here, the chromatic dispersion of a standard single mode optical fiber (SMF) at a wavelength of 1550 nm is represented by D
_The dispersion slope is represented by _SMF and represented by _SMF . The chromatic dispersion of the non-zero dispersion shifted optical fiber (NZDSF) at a wavelength of 1550 nm is represented by D _DSF and the dispersion slope is represented by S _DSF . The wavelength of the dispersion compensating optical fiber (DCF) is 1550 nm.
_Is represented by D _DCF and the dispersion slope is represented by S _DCF . At this time, in order to reduce the absolute value of the accumulated chromatic dispersion of the optical transmission line in a wide band including the wavelength of 1550 nm, a dispersion compensating optical fiber (which compensates for both the chromatic dispersion and the dispersion slope of a standard single mode optical fiber). hereinafter referred to as "SMF dispersion compensating optical fiber".), the ratio of the chromatic dispersion D _DCF and dispersion slope _{S DCF (S DCF / D DCF} )
, It is required substantially equal to a ratio between chromatic dispersion D _SMF of the single-mode optical fiber and the dispersion slope _{S SMF (S SMF / D SM} F). Also, a dispersion compensating optical fiber that compensates for both the chromatic dispersion and the dispersion slope of the dispersion-shifted optical fiber (hereinafter referred to as “DSF dispersion compensating optical fiber”)
In, the ratio of the chromatic dispersion D _DCF and dispersion slope S _DCF (S _{D CF}
/ D _DCF ) is required to be substantially equal to the ratio (S _DSF / D _DSF ) between the chromatic dispersion D _DSF and the dispersion slope S _DSF of the dispersion-shifted optical fiber.

[0006]

As compared with a standard single mode optical fiber, a dispersion shifted optical fiber has a larger ratio (S _DSF / D _DSF ) at a wavelength of 1550 nm. Therefore, compared with the dispersion compensating optical fiber for SMF, D
The dispersion-compensating optical fiber for SF needs to have a large ratio (S _DCF / D _DCF ) at a wavelength of 1550 nm.

The dispersion compensating optical fiber for SMF disclosed in Japanese Patent Application Laid-Open No. 6-11620 is a standard single mode optical fiber having a zero dispersion wavelength near 1.3 μm and a large chromatic dispersion at 1550 nm. Compensates for chromatic dispersion, and has negative chromatic dispersion having a large absolute value. Therefore, this dispersion compensating optical fiber for SMF is suitable for compensating the chromatic dispersion of a standard single mode optical fiber. However, this SM
The dispersion compensating optical fiber for F is not enough to compensate the dispersion slope.

On the other hand, the dispersion compensating optical fiber for DSF disclosed in US Pat. No. 5,838,867 has a wavelength of 1
Both chromatic dispersion and dispersion slope of a non-zero dispersion shifted optical fiber having a small positive chromatic dispersion at 550 nm can be compensated. However, since the dispersion compensating optical fiber for DSF has a small absolute value of the chromatic dispersion, a long dispersion compensating optical fiber for DSF is required to compensate for both the chromatic dispersion and the dispersion slope of the non-zero dispersion shifted optical fiber. Becomes

For example, in Reference 1, "S. Bigo, et al.," 1.5
Terabit / s WDM transmission of 150 channels at 10 G
bit / s over 4x100km of TeraLight ^TM fiber ", ECOC'99,
The non-zero dispersion shifted optical fiber disclosed in "PD (1999)" has a chromatic dispersion of +8 ps / wavelength at a wavelength of 1550 nm.
nm / km and the dispersion slope is +0.06 ps / n
m ² / km. Reference 2 “DW Peckham, et a
l., "Reduced dispersion slope, non-zero dispersion
fiber ", ECOC'98, pp. 139-140 (1998)", the chromatic dispersion is +4 ps / nm / km and the dispersion slope is +0.046 ps / at a wavelength of 1550 nm. nm ² / km. The non-zero dispersion shifted optical fiber 80 disclosed in these documents
To compensate for both the chromatic dispersion of km and the dispersion slope, a dispersion compensating optical fiber for DSF having a length of 8 km to 16 km is required.

In general, a dispersion compensating optical fiber for DSF is liable to leak the fundamental mode light even with a slight bending.
Since the bending loss of the fundamental mode light is large, the transmission loss increases when the cable is laid and laid or wound around a coil to form a dispersion compensation module. Therefore, in an optical transmission system that performs optical communication by transmitting signal light to an optical transmission line configured by connecting a dispersion-shifted optical fiber and a DSF dispersion-compensating optical fiber, the transmission loss in the optical transmission line is large. Therefore, the relay section cannot be lengthened, and it is not possible to further increase the speed and capacity of the optical communication.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a dispersion compensation optical fiber capable of compensating chromatic dispersion and dispersion slope of a non-zero dispersion shift optical fiber in a short length. An optical transmission line including an optical fiber and a dispersion compensating optical fiber and having a small transmission loss, and a dispersion compensating module having a small transmission loss, wherein the dispersion compensating optical fiber is wound into a coil and modularized. I do.

[0012]

SUMMARY OF THE INVENTION A dispersion compensating light according to the present invention.
The fiber has a chromatic dispersion D at 1550 nm.
_DCFIs -40 ps / nm / km or less, and the chromatic dispersion D
_DCFAnd dispersion slope S_DCFAnd the ratio (S_DCF/ D_DCF) Is 0.
005 / nm or more. In addition,
More preferably, the dispersion compensating optical fiber according to
D_DCFIs -100 ps / nm / km to -40 ps / n
m / km and the chromatic dispersion D_DCFAnd dispersion slope S_DCFWhen
Ratio (S_DCF/ D_DCF) Is 0.005 / nm to 0.015
/ Nm. This dispersion compensating optical fiber
Is the chromatic dispersion D_DCFIs negative, the absolute value is large, and the wave
Long dispersion D_DCFAnd dispersion slope S_DCFAnd the ratio (S_DCF/
D_DCF) Is as above,
Dispersion-shifted light in a wide wavelength band including a wavelength of 1550 nm
Compensates fiber chromatic dispersion and dispersion slope in short length
Can be

The dispersion compensating optical fiber according to the present invention has an effective area of 20 μm ^{2 at} a wavelength of 1550 nm.
It is characterized by the above. In this case, generation of four-wave mixing can be suppressed, and deterioration of the waveform of the propagating signal light can be suppressed.

Further, the dispersion compensating optical fiber according to the present invention is characterized in that the cut-off wavelength is 1.2 μm to 1.8 μm (more preferably, 1.4 μm to 1.8 μm). The dispersion compensating optical fiber according to the present invention has a wavelength of 1
The transmission loss at 550 nm is 0.5 dB / km or less. In this case, since the cutoff wavelength is longer than the conventional one, the increase in bending loss can be suppressed, and the numerical range of the transmission loss is as described above. Or even if it is modularized, the loss is low.

Further, the dispersion compensating optical fiber according to the present invention comprises a central core region having a first refractive index and a first cladding surrounding the central core region and having a second refractive index smaller than the first refractive index. A region, a second cladding region surrounding the first cladding region and having a third refractive index larger than the second refractive index, and a fourth refractive index surrounding the second cladding region and being smaller than the third refractive index. And a third cladding region. The relative refractive index difference of the central core region with respect to the fourth refractive index of the third cladding region is 0.8% to 1.5%. Further, a difference in the relative refractive index of the first cladding region with respect to the fourth refractive index of the third cladding region is −0.4% or less. These cases are suitable for realizing a dispersion compensating optical fiber having the above characteristics.

Further, the dispersion compensating optical fiber according to the present invention is characterized in that the change in the ratio (S _DCF / D _DCF ) to the change in the outer diameter of the second cladding region by 2% is 10% or less. I do. In this case, it is easy to manufacture a dispersion compensating optical fiber having desired wavelength dispersion characteristics.

The optical transmission line according to the present invention has a wavelength of 1550n.
m, the chromatic dispersion is +2 ps / nm / km to +10 p
s / nm / km and the dispersion slope is +0.04 ps /
nm ^Two/Km~+0.12ps/nm^Two/ Dispersion which is / km
Shift optical fiber and connection with this dispersion shift optical fiber
And the dispersion compensating optical fiber according to the present invention described above,
It is laid in the joint section. This optical transmission
The path consists of a dispersion-shifted optical fiber and a dispersion-compensating optical fiber.
By connecting with an appropriate length ratio, the wavelength 1550n
m, the absolute value of the entire average chromatic dispersion is small,
The absolute value of the average dispersion slope of the body is also small. This allows
This optical transmission line has a wide wavelength band including a wavelength of 1550 nm.
Therefore, the absolute value of the average chromatic dispersion is small, and the optical transmission path is
The overall average transmission loss is also small.

In the optical transmission line according to the present invention, the deviation (= maximum value−minimum value) of the entire average chromatic dispersion in the wavelength band of 1535 nm to 1560 nm (C band) is 0.2 p.
s / nm / km or less. More preferably, the deviation of the entire average chromatic dispersion in the wavelength band of 1535 nm to 1600 nm (C band and L band) is 0.2 ps / nm / km or less.
In this case, an optical transmission system that performs optical communication by propagating signal light through such an optical transmission line has a wide wavelength band including a wavelength of 1550 nm (a wavelength band including at least the C band and further including the L band). ), The average transmission loss of the optical transmission line is small, the absolute value of the average chromatic dispersion is small, and optical transmission at a high bit rate is possible. Therefore, in this optical transmission system, the relay section can be lengthened, and the speed and capacity of optical communication can be further increased.

The dispersion compensating module according to the present invention is characterized in that the dispersion compensating optical fiber according to the present invention is wound into a coil and modularized. The dispersion compensation module in which the dispersion compensation optical fiber is modularized compensates for the chromatic dispersion and dispersion slope of the dispersion shift optical fiber laid in the relay section, and the dispersion shift optical fiber and the dispersion compensation optical fiber are By setting the appropriate length ratio, at a wavelength of 1550 nm, the absolute value of the entire average chromatic dispersion is small, and the absolute value of the entire average dispersion slope is also small. As a result, the entire dispersion-shifted optical fiber and the dispersion compensation module have a small absolute value of the average chromatic dispersion and a small average transmission loss in a wide wavelength band including the wavelength of 1550 nm.

The dispersion compensation module according to the present invention has a dispersion compensation amount of -640p at a wavelength of 1550 nm.
When s / nm, the wavelength band is 1535 nm to 156 nm.
The total loss at 5 nm is 7 dB or less, and more preferably, the wavelength band is 1535 nm to 1610 n
m, the total loss is 7 dB or less. The dispersion compensating module according to the present invention has a wavelength 1
When the dispersion compensation amount at 550 nm is -320 ps / nm, the total loss is 3 dB or less in a wavelength band of 1535 nm to 1565 nm, and more preferably, the total loss is 3 dB or less in a wavelength band of 1535 nm to 1610 nm. There is a feature. An optical transmission system having this dispersion compensation module has a wavelength of 155.
In a wide wavelength band including 0 nm (a wavelength band including at least the C band and further including the L band), the average transmission loss is small, the absolute value of the average chromatic dispersion is small, and high bit rate optical transmission is possible. . Therefore, in this optical transmission system, the relay section can be lengthened, and the speed and capacity of optical communication can be further increased.

The dispersion compensating optical fiber according to the present invention has a wavelength
At 1550 nm, the chromatic dispersion D _DCFIs -40ps /
nm / km or less, and the chromatic dispersion D_DCFAnd dispersion slope
S_DCFAnd the ratio (S_DCF/ D_DCF) Is 0.005 / nm or more
And the effective area is 20 μm ^TwoIt is characteristic that it is above
And This dispersion compensating optical fiber has a wavelength of 1550 nm.
Over a wide wavelength band, including
Scatter and dispersion slope can be compensated for on a short scale.
Signal light, which suppresses the generation of four-wave mixing
Can be suppressed from deteriorating.

The dispersion compensating optical fiber according to the present invention has a wavelength
At 1550 nm, the chromatic dispersion D _DCFIs -40ps /
nm / km or less, and the chromatic dispersion D_DCFAnd dispersion slope
S_DCFAnd the ratio (S_DCF/ D_DCF) Is 0.005 / nm or more
And that the transmission loss is 0.5 dB / km or less.
Features. This dispersion compensating optical fiber has a wavelength of 1550.
Wavelength of dispersion shifted optical fiber in a wide wavelength band including nm
Long dispersion and dispersion slope can be compensated for on a short scale.
Not only cabled or modularized
However, the loss is low.

[0023]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1 is a schematic configuration diagram of an optical transmission system 1 including an optical transmission line 30 according to the present embodiment. The optical transmission system 1 includes an optical transmission line 3 in a relay section between a station (transmitting station or relay station) 10 and a station (receiving station or relay station) 20.
0 is laid. The optical transmission line 30 is formed by fusion-splicing a dispersion-shifted optical fiber 31 and a dispersion-compensating optical fiber 32. In this optical transmission system 1,
The multi-wavelength signal light in the 1.55 μm band transmitted from the station 10 propagates through the dispersion-shifted optical fiber 31 and the dispersion-compensating optical fiber 32 to reach the station 20 and is received by the station 20, or At 20, the light is amplified and sent further downstream.

The dispersion-shifted optical fiber 31 has a wavelength of 155
It is a silica-based optical fiber having a small positive chromatic dispersion at 0 nm. This dispersion-shifted optical fiber 31 has a chromatic dispersion D _DSF of +2 ps / wavelength at a wavelength of 1550 nm.
nm / km to +10 ps / nm / km, and the dispersion slope S _DSF is +0.04 ps / nm ² / km to +0.12.
ps / nm ² / km and the transmission loss is 0.20 dB /
km.

The dispersion compensating optical fiber 32 according to the present embodiment
Is at a wavelength of 1550 nm of the dispersion-shifted optical fiber 31.
Silica Base Compensates for Chromatic Dispersion and Dispersion Slope
Optical fiber. This dispersion compensating optical fiber 32
Is the chromatic dispersion D at a wavelength of 1550 nm._DCFIs -4
0 ps / nm / km or less, and the chromatic dispersion D_DCFAnd dispersion
Slope S_DCFAnd the ratio (S_DCF/ D_DCF) Is 0.005 /
nm or more. More preferably, the dispersion compensating optical fiber
The beam 32 has a chromatic dispersion D at a wavelength of 1550 nm. _DCF
Is -100 ps / nm / km to -40 ps / nm / km
And the chromatic dispersion D_{D CF}And dispersion slope S_DCFAnd the ratio (S
_DCF/ D_DCF) Is 0.005 / nm to 0.015 / nm
is there. The dispersion compensating optical fiber 32 has a wavelength
20 μm effective area at 50 nm^TwoThat's it,
The cutoff wavelength is from 1.2 μm to 1.8 μm (more preferably
Is 1.4 μm to 1.8 μm), and the wavelength is 1550 nm.
, The transmission loss is 0.5 dB / km or less.

The dispersion compensating optical fiber 32 having such characteristics has a wavelength of 1550, because the numerical ranges of the chromatic dispersion D _DCF and the dispersion slope S _DCF are as described above.
In a wide wavelength band including nm, the dispersion-shifted optical fiber 31
Can be compensated for in a short length. In addition, the dispersion compensating optical fiber 32 suppresses the generation of four-wave mixing and the deterioration of the waveform of the signal light to be propagated because the numerical range of the chromatic dispersion is as described above and the effective area is sufficient. can do. Further, in the dispersion compensating optical fiber 32, since the numerical range of the cutoff wavelength is as described above, an increase in bending loss can be suppressed, and the numerical range of the transmission loss is as described above. Accordingly, even when the cable is used, the optical transmission line 30 has low loss.

An optical transmission line 30 in which a dispersion-shifted optical fiber 31 and a dispersion-compensating optical fiber 32 are connected at an appropriate length ratio.
At a wavelength of 1550 nm, the absolute value of the overall average chromatic dispersion is small, and the absolute value of the overall average dispersion slope is also small. Thus, the optical transmission line 30 has a wavelength of 1550 nm.
, The absolute value of the entire average chromatic dispersion becomes small in a wide wavelength band including Further, the optical transmission path 30 has a small average transmission loss as a whole. The deviation of the average chromatic dispersion of the entire optical transmission line 30 is:
It is preferably 0.2 ps / nm / km or less in a wavelength band of 1535 nm to 1560 nm (C band), and more preferably 0.2 ps / nm / km or less in a wavelength band of 1535 nm to 1600 nm (C band and L band). is there. The optical transmission system 1 that performs optical communication by propagating signal light through such an optical transmission path 30 has a wavelength of 1550 nm.
In a wide wavelength band (including at least the C band and also including the L band), the average transmission loss of the optical transmission line 30 is small, the absolute value of the average chromatic dispersion is small, and the optical transmission at a high bit rate is performed. Is possible. Therefore, the optical transmission system 1 can lengthen the relay section,
The speed and capacity of optical communication can be further increased.

FIG. 2 is a schematic configuration diagram of an optical transmission system 2 in which a dispersion-shifted optical fiber 31 is laid as an optical transmission line and a dispersion-compensating optical fiber 32 is provided in the station 20 as a dispersion-compensating module. In this optical transmission system 2, a dispersion-shifted optical fiber 31 is laid as an optical transmission line in a relay section between a station (transmitting station or relay station) 10 and a station (receiving station or relay station) 20. . In this optical transmission system 2, the wavelength 1.55 μm transmitted from the station 10 is used.
The m-band multi-wavelength signal light propagates through the dispersion-shifted optical fiber 31, which is an optical transmission line, and reaches the station 20, where the signal is optically amplified by the optical amplifier 21 and the dispersion compensating light as a dispersion compensating module. The dispersion is compensated by the fiber 32, further amplified by the optical amplifier 22, and thereafter received or sent further downstream.

The dispersion-shifted optical fiber 31 used as an optical transmission line in the optical transmission system 2 of FIG. 2 is a dispersion-shifted optical fiber 31 used as a part of the optical transmission line in the optical transmission system 1 of FIG. It has the same features as described above. The dispersion compensating optical fiber 32 used as a dispersion compensating module in the optical transmission system 2 of FIG. 2 is different from the dispersion compensating optical fiber 32 used as a part of the optical transmission line in the optical transmission system 1 of FIG. They have similar features. However, in the optical transmission system 2 shown in FIG. 2, the dispersion compensating optical fiber 32 is wound around a bobbin in a coil shape to be modularized and provided in the station 20.

The dispersion compensating optical fiber 32 having the above-described characteristics has a wavelength of 1550 due to the numerical ranges of the chromatic dispersion D _DCF and the dispersion slope S _DCF as described above.
In a wide wavelength band including nm, the dispersion-shifted optical fiber 31
Can be compensated for in a short length. In addition, the dispersion compensating optical fiber 32 suppresses the generation of four-wave mixing and the deterioration of the waveform of the signal light to be propagated because the numerical range of the chromatic dispersion is as described above and the effective area is sufficient. can do. Further, in the dispersion compensating optical fiber 32, since the numerical range of the cutoff wavelength is as described above, an increase in bending loss can be suppressed, and the numerical range of the transmission loss is as described above. Therefore, even if it is modularized, the loss is low.

A dispersion-shifted optical fiber 3 as an optical transmission line
1 and a dispersion compensating optical fiber 3 as a dispersion compensating module
By setting each of the lengths to an appropriate length, the absolute value of the average chromatic dispersion and the absolute value of the average dispersion slope are small at a wavelength of 1550 nm. As a result, the dispersion-shifted optical fiber 31 and the dispersion-compensating optical fiber 32 as a whole have a small absolute value of the average chromatic dispersion in a wide wavelength band including the wavelength of 1550 nm, and a small average transmission loss. The deviation of the overall average chromatic dispersion is preferably 0.2 ps / nm / km or less in a wavelength band of 1535 nm to 1560 nm (C band), and more preferably a wavelength band of 1535 nm to 1600 nm (C band and L band). Is 0.2 ps / nm / km or less.

The dispersion compensating optical fiber 32 as the dispersion compensating module preferably has a total loss of 7 dB in a wavelength band of 1535 nm to 1565 nm (C band) when the amount of dispersion compensation at a wavelength of 1550 nm is -640 ps / nm. Below, more preferably the wavelength band 15
The total loss is 7 dB or less between 35 nm and 1610 nm (C band and L band). The dispersion compensating optical fiber 32 as a dispersion compensating module has a wavelength of 155.
When the dispersion compensation amount at 0 nm is -320 ps / nm, the wavelength band is preferably 1535 nm to 1565 nm.
The total loss in the (C band) is 3 dB or less, and more preferably the total loss in the wavelength band of 1535 nm to 1610 nm (C band and L band) is 3 dB or less.

This optical transmission system 2 has a wavelength of 1550n.
In a wide wavelength band including m (a wavelength band including at least the C band and also including the L band), the average transmission loss is small, the absolute value of the average chromatic dispersion is small, and high bit rate optical transmission is possible. . Therefore, the optical transmission system 2 can lengthen the relay section, and can further increase the speed and capacity of optical communication.

FIG. 3 is a view for explaining a preferred example of the refractive index profile of the dispersion compensating optical fiber 32 according to the present embodiment. As shown in this figure, the dispersion compensating optical fiber 32
Is a central core region including the optical axis center (refractive index n ₁ , outer diameter 2
a), a first cladding region surrounding this central core region (refractive index n ₂ , outer diameter 2b), and a second cladding region surrounding this first cladding region (refractive index n ₃ , outer diameter 2c)
And a third cladding region (refractive index n ₄ ) surrounding the second cladding region. The magnitude relation of each refractive index is
_{n 2 <n 4 <n 3} < a n _1. The dispersion compensating optical fiber 32 has a relative refractive index difference Δn _{1 in} the central core region of 0.8% to 1.0 with reference to the refractive index n ₄ of the third cladding region.
5%, and the relative refractive index difference Δn _{2 of} the first cladding region is −
0.4% or less. Note that represents the relative refractive index difference of the second cladding region when the refractive index n ₄ of the third cladding region as a reference and the [Delta] n _3.

With such a refractive index profile, the dispersion compensating optical fiber 32 has a wavelength of 1550 nm.
At m, the chromatic dispersion D _DCF , the ratio (S _DCF / D _DCF ), the effective area, the cutoff wavelength, and the transmission loss fall within the above numerical ranges. The dispersion compensating optical fiber 32 having such a refractive index profile is based on silica glass, and GeO ₂ is added to the central core region, and the
F element is added to the cladding region, and G is added to the second cladding region.
It is preferred to add eO ₂ . By doing so, the refractive index profile shown in FIG. 3 can be realized, and the wavelength 1550 of the dispersion compensating optical fiber 32 can be realized.
The transmission loss in nm can be reduced.

Next, a specific example of the dispersion compensating optical fiber 32 according to the present embodiment will be described. Each of the dispersion compensation optical fiber DCF1 of the first embodiment and the dispersion compensation optical fiber DCF2 of the second embodiment described below has a refractive index profile shown in FIG.

The dispersion compensating optical fiber DCF1 of the first embodiment
Is the relative refractive index difference Δn of the central core region. ₁To 1.2%,
Relative refractive index difference Δn of the first cladding region_TwoWith -0.50%
And the relative refractive index difference Δn of the second cladding region._Three0.20%
And each of the central core region and the second cladding region
The outer diameter ratio (2a / 2c) is 0.30, and the first clad
The ratio of the outer diameter of each of the region and the second cladding region (2b
/ 2c) was set to 0.60. And this second
In one embodiment, the dispersion compensating optical fiber DCF1 is
When the outer diameter 2c of the storage region is 17.7 μm, the wavelength 1
At 550 nm, the chromatic dispersion D_DCFIs -62.4ps
/ Nm / km and the dispersion slope S_DCFIs -0.44
ps / nm^Two/ Km and an effective area of 24.4 μm^Two
And the bending loss at a bending diameter of 20 mmφ is 10 dB / m.
And the transmission loss is 0.30 dB / km,
The off wavelength was 1224 nm. In addition, wavelength 1550
in nm (S_DCF/ D_DCF) Is 0.0071 / nm
Met.

The dispersion compensating optical fiber DCF2 of the second embodiment
Is the relative refractive index difference Δn of the central core region. ₁Is 1.3%,
Relative refractive index difference Δn of the first cladding region_TwoWith -0.50%
And the relative refractive index difference Δn of the second cladding region._Three0.23%
And each of the central core region and the second cladding region
The outer diameter ratio (2a / 2c) is 0.27, and the first clad
The ratio of the outer diameter of each of the region and the second cladding region (2b
/ 2c) was set to 0.55. And this second
The dispersion compensating optical fiber DCF2 of the second embodiment is
When the outer diameter 2c of the storage region is 19.0 μm, the wavelength 1
At 550 nm, the chromatic dispersion D_DCFIs -80.4ps
/ Nm / km and the dispersion slope S_DCFIs -0.59
ps / nm^Two/ Km and an effective area of 23.9 μm^Two
And the bending loss at a bending diameter of 20 mmφ is 4 dB / m.
With transmission loss of 0.33 dB / km and cut-off
Wavelength was 1576 nm. In addition, wavelength 1550n
m (S_DCF/ D_DCF) Is 0.0073 / nm
there were.

FIG. 4 is a graph showing the relationship between the chromatic dispersion at a wavelength of 1550 nm and the dispersion slope of the dispersion compensating optical fiber of each embodiment. Here, the relationship between the chromatic dispersion D _DCF and the dispersion slope S _DCF when the outer diameter 2c of the second cladding region of the dispersion compensating optical fiber of each embodiment is changed is shown. As can be seen from this graph, each of the dispersion compensating optical fibers DCF1 and DCF2 has a chromatic dispersion D _DCF of approximately −60 even if the outer diameter 2c of the second cladding region changes.
Within the range of ps / nm / km to -10 ps / nm / km, the ratio ( _Sd) of the chromatic dispersion D _DCF to the dispersion slope S _DCF
DCF / D _DCF ) is small. The dispersion compensating optical fiber DCF1 of the first embodiment has an outer diameter 2c of the second cladding region 2c.
2.5% change in ratio (S _DCF / D _DCF ) to% change
It is as follows. Further, the dispersion compensating optical fiber D of the second embodiment
CF2 has a ratio (S _DCF / D _DCF ) change of 9.0% or less with respect to a change of 2% of the outer diameter 2c of the second cladding region. If this way, a change in the ratio (S _DCF / _D D _CF) against 2% change in the outside diameter 2c of the second cladding region is 10% or less, the dispersion compensating optical fiber having a desired wavelength dispersion characteristics Easy to manufacture.

FIG. 5 is a graph showing the wavelength dependence of the bending loss of the dispersion compensating optical fiber of each embodiment at a bending diameter of 140 mmφ. Here, the outer diameter 2c of the first cladding region of the dispersion compensating optical fiber DCF1 of the first embodiment is set to 17.7 μm.
m, and the outer diameter 2c of the second cladding region of the dispersion compensating optical fiber DCF2 of the second embodiment was 19.0 μm. As can be seen from this graph, each of the dispersion compensating optical fibers DCF1 and DCF2 has a small bending loss in a wavelength range of 1610 nm or less.

Therefore, the dispersion compensating optical fiber DCF1
And the DCF 2, the dispersion compensating optical fiber 3 as a part of the optical transmission line 30 of the optical transmission system 1 shown in FIG.
2 as well as a dispersion compensating optical fiber 32 as a dispersion compensating module of the optical transmission system 2 shown in FIG. Can be compensated for.

FIG. 6 is a graph showing the wavelength dependence of the chromatic dispersion of the dispersion compensating optical fiber of each embodiment. even here,
The outer diameter 2c of the first cladding region of the dispersion compensating optical fiber DCF1 of the first embodiment is set to 17.7 μm, and the outer diameter 2c of the second cladding region of the dispersion compensating optical fiber DCF2 of the second embodiment is set to 27.7 μm.
c was set to 19.0 μm. This figure also shows one example of the wavelength dependence of the chromatic dispersion of the dispersion-shifted optical fiber NZDSF.

FIG. 7 is a graph showing the wavelength dependence of the average chromatic dispersion of the entirety where the dispersion compensating optical fiber and the dispersion shift optical fiber of each embodiment are connected. To compensate for the chromatic dispersion at a wavelength of 1550 nm of the dispersion-shifted optical fiber NZDSF having a wavelength dispersion characteristic and having a length of 80 km shown in FIG.
A length of 0.3 km was required, and the dispersion compensating optical fiber DCF2 of the second embodiment required a length of 8.0 km.

The dispersion compensating optical fiber DSF1 of the first embodiment
In the case where the optical fiber and the dispersion-shifted optical fiber NZDSF were connected, the deviation of the entire average chromatic dispersion was 0.2 ps / nm / km or less in the wavelength band of 1535 nm to 1600 nm (C band and L band). Second Embodiment Dispersion Compensating Optical Fiber DSF2 and Dispersion Shifting Optical Fiber NZ
The wavelength band connected to DSF is 1535nm ~
At 1560 nm (C band), the deviation of the entire average chromatic dispersion was 0.2 ps / nm / km or less. Therefore, these can perform optical transmission with a relay distance of 400 km at a bit rate of 40 Gb / s.

When the dispersion compensating optical fiber DCF1 of the first embodiment having a length of 10.3 km is wound with a bending diameter of 140 mmφ to form a dispersion compensating module, the dispersion compensation amount at a wavelength of 1550 nm is -640 ps / nm. In a wavelength band of 1535 nm to 1610 nm (C band and L band), the maximum value of the total loss is 4.1 dB (＠wavelength 1
530 nm). When the dispersion compensating optical fiber DCF2 of the second embodiment having a length of 8.0 km is wound with a bending diameter of 140 mmφ to form a dispersion compensating module, the wavelength is 1550 nm.
Is −640 ps / nm, and the wavelength band is 1535 nm to 1610 nm (C band and L band).
Band), the maximum value of the total loss was 4.4 dB (＠wavelength 1530 nm).

The dispersion compensating optical fiber D of the first embodiment
CF1 was wound at a bending diameter of 140 mmφ to form a dispersion compensation module, and the dispersion compensation amount at a wavelength of 1550 nm was −320.
When ps / nm is set, the wavelength band is 1535 nm to 161 nm.
At 0 nm (C band and L band), the maximum value of the total loss was 2.3 dB (＠ wavelength 1530 nm). The dispersion compensating optical fiber DCF2 of the second embodiment is
mmφ to make a dispersion compensating module, wavelength 1550n
When the dispersion compensation amount at m is -320 ps / nm, the maximum value of the total loss is 2.5 dB in the wavelength band of 1535 nm to 1610 nm (C band and L band).
(＠Wavelength 1530 nm).

As described above, the dispersion compensating optical fiber DCF1
And the DCF 2 can compensate for the chromatic dispersion and dispersion slope of the dispersion-shifted optical fiber NZDSF in a short wavelength and at a low loss in a wide wavelength band including a wavelength of 1550 nm.

Next, for comparison with the dispersion compensating optical fibers of the above embodiments, a dispersion compensating optical fiber of a comparative example will be described. FIG. 8 is a diagram illustrating the refractive index profile of the dispersion compensating optical fiber of the comparative example. The dispersion compensating optical fiber of this comparative example has a central core region including the center of the optical axis (refractive index n ₁ , outer diameter 2a) and a first cladding region surrounding the central core region (refractive index n ₂ , outer diameter 2b). And a second cladding region (refractive index n ₃ ) surrounding the first cladding region. The relationship between the refractive indices is n ₂ <n
₃ <is n _1. The relative refractive index difference Δn ₁ of the central core region is 1.2 with reference to the refractive index n ₃ of the second cladding region.
%, And the relative refractive index difference Δn _{2 of} the first cladding region is −
0.36% or less. The outer diameter 2a of the central core region and the first
The ratio Ra (= 2a / 2b) with respect to the outer diameter of the cladding region is equal to 0.
50.

FIG. 9 is a graph showing the relationship between chromatic dispersion and dispersion slope at a wavelength of 1550 nm of the dispersion compensating optical fiber of the comparative example. Here, the relationship between the chromatic dispersion D _DCF and the dispersion slope S _DCF when the outer diameter 2b of the first cladding region of the dispersion compensation optical fiber of the comparative example is changed is shown. The dispersion compensating optical fiber of this comparative example has a chromatic dispersion of −
In the range of 40 ps / nm / km or less, the bending characteristics are poor, and it cannot be used. Further, when the outer diameter 2c of the second cladding region changes, the ratio (S _DCF / D _DCF ) between the chromatic dispersion D _DCF and the dispersion slope S _DCF changes greatly.
For example, when the outer diameter 2b of the first cladding region is 10.0 μm, the chromatic dispersion D _DCF is −28 ps / nm / km, and the dispersion slope S _DCF is −0.081 ps / nm ₂ /
km, and the ratio (S _DCF / D _DCF ) changes by 17% when the outer diameter 2b changes by 2% from the center. Therefore, it is difficult to manufacture a dispersion compensating optical fiber having desired chromatic dispersion characteristics.

As compared with the dispersion compensating optical fiber of the comparative example, the dispersion compensating optical fiber according to the present embodiment (including the dispersion compensating optical fibers of the first and second examples) is as described above. Even in the range where the chromatic dispersion is -40 ps / nm / km or less, the material has excellent bending characteristics and can be used. Also, the dispersion compensating optical fiber according to the present embodiment, even if the outer diameter 2c of the second cladding region is changed, as long as it is within the range the chromatic dispersion D _DCF is constant, the wavelength dispersion D _DCF and dispersion slope S _DCF Of the ratio (S _DCF / D _DCF ) is small. Therefore, it is easy to manufacture the dispersion compensating optical fiber according to the present embodiment having desired wavelength dispersion characteristics.

[0052]

As described above in detail, the dispersion compensating optical fiber according to the present invention has a chromatic dispersion D _DCF of -40 ps / nm / km or less (more preferably -100 ps / nm / km) at a wavelength of 1550 nm. ~ -40ps / n
m is / miles), the dispersion slope S _DCF chromatic dispersion D _{DC F}
(S _DCF / D _DCF ) is 0.005 / nm or more (more preferably 0.005 / nm to 0.015 / nm). With such characteristics, the dispersion compensating optical fiber according to the present invention can compensate the chromatic dispersion and dispersion slope of the dispersion-shifted optical fiber in a short wavelength in a wide wavelength band including a wavelength of 1550 nm.

The dispersion compensating optical fiber according to the present invention has an effective area of 20 μm ^{2 at} a wavelength of 1550 nm.
In the case described above, the occurrence of four-wave mixing can be suppressed, and the deterioration of the waveform of the propagating signal light can be suppressed. Further, it is preferable that the cutoff wavelength is 1.2 μm to 1.8 μm (more preferably, 1.4 μm to 1.8 μm), and the transmission loss is 0.5 μm at a wavelength of 1550 nm.
It is preferably at most dB / km. In this case,
Since the cutoff wavelength is longer than the conventional one, it is possible to suppress the increase in bending loss, and further, when combined with the fact that the numerical range of the transmission loss is as described above, when a cable or a module is used. However, the loss is low.

Further, the dispersion compensating optical fiber according to the present invention comprises a central core region having a first refractive index and a first cladding surrounding the central core region and having a second refractive index smaller than the first refractive index. A region, a second cladding region surrounding the first cladding region and having a third refractive index larger than the second refractive index, and a fourth refractive index surrounding the second cladding region and being smaller than the third refractive index. It is preferable to have a third cladding region having the same. Further, it is preferable that the relative refractive index difference of the central core region with respect to the fourth refractive index of the third cladding region is 0.8% to 1.5%, It is preferable that the relative refractive index difference of the first cladding region based on the refractive index of No. 4 is −0.4% or less. In these cases, a dispersion compensating optical fiber having the above characteristics can be easily realized.
In addition, it is preferable that the change in the ratio (S _DCF / D _DCF ) is not more than 10% with respect to the change in the outer diameter of the second cladding region by 2%. It is easy to manufacture a dispersion compensating optical fiber having the same.

The optical transmission line according to the present invention has a wavelength of 1550n.
m, the chromatic dispersion is +2 ps / nm / km to +10 p
s / nm / km and the dispersion slope is +0.04 ps /
nm ^Two/Km~+0.12ps/nm^Two/ Dispersion which is / km
Shift optical fiber and connection with this dispersion shift optical fiber
And the dispersion compensating optical fiber according to the present invention described above,
It is laid in the joint section. This optical transmission line uses dispersion shift
The optical fiber and the dispersion compensating optical fiber are connected at an appropriate length ratio.
At a wavelength of 1550 nm,
The absolute value of the average chromatic dispersion of the
The absolute value of the loop is also small. As a result, this optical transmission line
In a wide wavelength band including a wavelength of 1550 nm, the entire average wave
The absolute value of long dispersion is small, and the overall average transmission loss is also small.
No.

Further, in the optical transmission line according to the present invention, it is preferable that the deviation of the entire average chromatic dispersion in the wavelength band of 1535 nm to 1560 nm (C band) is 0.2 ps / nm / km or less. Has a wavelength band of 1535
The deviation of the total average chromatic dispersion from 0.2 nm to 1600 nm (C band and L band) is 0.2 ps / nm / km.
It is as follows. In this case, an optical transmission system that performs signal communication by propagating signal light through such an optical transmission line has a wavelength of 1 wavelength.
In a wide wavelength band including 550 nm (a wavelength band including at least the C band and also including the L band), the average transmission loss of the optical transmission line is small, the absolute value of the average chromatic dispersion is small, and the optical transmission at a high bit rate is performed. Is possible. Therefore, in this optical transmission system, the relay section can be lengthened, and the speed and capacity of optical communication can be further increased.

The dispersion compensating module according to the present invention is a module in which the above-described dispersion compensating optical fiber according to the present invention is wound into a coil shape to be modularized. The dispersion compensation module in which the dispersion compensation optical fiber is modularized compensates for the chromatic dispersion and dispersion slope of the dispersion shift optical fiber laid in the relay section, and the dispersion shift optical fiber and the dispersion compensation optical fiber are By setting the appropriate length ratio, at a wavelength of 1550 nm, the absolute value of the entire average chromatic dispersion is small, and the absolute value of the entire average dispersion slope is also small. As a result, the entire dispersion-shifted optical fiber and the dispersion compensation module have a small absolute value of the average chromatic dispersion and a small average transmission loss in a wide wavelength band including the wavelength of 1550 nm.

The dispersion compensation module according to the present invention has a dispersion compensation amount of -640p at a wavelength of 1550 nm.
When s / nm, the wavelength band is 1535 nm to 156 nm.
The total loss at 5 nm is preferably 7 dB or less, and more preferably, the wavelength band is 1535 nm to 1610 n.
At m, the total loss is 7 dB or less. The dispersion compensation module according to the present invention has a total loss of 3 dB in a wavelength band of 1535 nm to 1565 nm when the dispersion compensation amount at a wavelength of 1550 nm is −320 ps / nm.
Preferably, the wavelength band 1
Total loss is 3 dB or less from 535 nm to 1610 nm. The optical transmission system having the dispersion compensation module has a wide wavelength band including a wavelength of 1550 nm (a wavelength band including at least the C band and further including the L band).
Thus, the average transmission loss is small, the absolute value of the average chromatic dispersion is small, and optical transmission at a high bit rate is possible. Therefore, in this optical transmission system, the relay section can be lengthened, and the speed and capacity of optical communication can be further increased.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an optical transmission system including an optical transmission line according to an embodiment.

FIG. 2 is a schematic configuration diagram of an optical transmission system in which a dispersion-shifted optical fiber is laid as an optical transmission line and a dispersion-compensating optical fiber is provided in a station as a dispersion-compensating module.

FIG. 3 is a diagram illustrating a preferred example of a refractive index profile of the dispersion compensating optical fiber according to the embodiment.

FIG. 4 shows a wavelength 1550 of the dispersion compensating optical fiber of each embodiment.
4 is a graph showing the relationship between chromatic dispersion in nm and dispersion slope.

FIG. 5 is a bending diameter 140 of the dispersion compensating optical fiber of each embodiment.
4 is a graph showing the wavelength dependence of bending loss in mmφ.

FIG. 6 is a graph showing the wavelength dependence of chromatic dispersion of the dispersion compensating optical fiber of each embodiment.

FIG. 7 is a graph showing the wavelength dependence of the average chromatic dispersion of the entirety where the dispersion compensating optical fiber and the dispersion shift optical fiber of each embodiment are connected.

FIG. 8 is a diagram illustrating a refractive index profile of a dispersion compensation optical fiber of a comparative example.

FIG. 9 shows a wavelength of 1550 n of the dispersion compensating optical fiber of the comparative example.
7 is a graph showing the relationship between chromatic dispersion and dispersion slope at m.

[Explanation of symbols]

1, 2, optical transmission system, 10, 20, station, 30 transmission line, 31 dispersion-shifted optical fiber, 32 dispersion-compensating optical fiber.

Claims (20)

[Claims] 1. A chromatic dispersion D at a wavelength of 1550 nm.
_DCF is -40 ps / nm / km or less, and chromatic dispersion D
The ratio of the _DCF to the dispersion slope S _DCF (S _DCF / D _{D CF} ) is 0.
A dispersion compensating optical fiber having a wavelength of 005 / nm or more. 2. A wavelength dispersion D at a wavelength of 1550 nm.
_DCF is -100 ps / nm / km to -40 ps / nm /
km, and the ratio of the chromatic dispersion D _DCF to the dispersion slope S _DCF (S _DCF / D _DCF ) is 0.005 / nm to 0.015 / n.
2. The dispersion compensating optical fiber according to claim 1, wherein m is m. 3. The dispersion-compensating optical fiber according to claim 1, wherein the effective area at the wavelength of 1550 nm is 20 μm ² or more. 4. A cut-off wavelength of 1.2 μm to 1.8 μm.
2. The dispersion compensating optical fiber according to claim 1, wherein m is m. 5. A cut-off wavelength of 1.4 μm to 1.8 μm.
The dispersion compensating optical fiber according to claim 4, wherein m is m. 6. The transmission loss at a wavelength of 1550 nm is 0.5 dB / km or less.
The dispersion compensating optical fiber according to the above. 7. A central core region having a first refractive index;
A first cladding region surrounding the central core region and having a second refractive index less than the first refractive index;
A second cladding region surrounding the cladding region and having a third refractive index greater than the second refractive index, and a third cladding surrounding the second cladding region and having a fourth refractive index less than the third refractive index 2. The dispersion-compensating optical fiber according to claim 1, comprising a region. 8. A relative refractive index difference of said central core region, based on a fourth refractive index of said third cladding region, is equal to 0.
8. The dispersion compensating optical fiber according to claim 7, wherein the amount is 8% to 1.5%. 9. The method according to claim 7, wherein a relative refractive index difference of the first cladding region with respect to a fourth refractive index of the third cladding region is −0.4% or less. Dispersion compensating optical fiber. 10. An outer diameter of 2% of an outer diameter of the second cladding region.
The ratio (S _DCF/ D_DCFIs less than 10%
8. The dispersion compensating optical fiber according to claim 7, wherein
Ba. 11. At a wavelength of 1550 nm, chromatic dispersion is +2 ps / nm / km to +10 ps / nm / km, and dispersion slope is +0.04 ps / nm ² / km to +10 ps / nm / km.
An optical transmission characterized in that a dispersion-shifted optical fiber of 0.12 ps / nm ² / km and the dispersion-compensating optical fiber according to claim 1 connected to the dispersion-shifted optical fiber are laid in a relay section. Road. 12. A wavelength band of 1535 nm to 1560 nm.
The deviation of the total average chromatic dispersion is 0.2 ps / nm
12. The optical transmission line according to claim 11, wherein the distance is equal to or less than / km. 13. A wavelength band of 1535 nm to 1600 nm.
The deviation of the total average chromatic dispersion is 0.2 ps / nm
13. The optical transmission line according to claim 12, wherein the distance is not more than / km. 14. A dispersion compensating module, wherein the dispersion compensating optical fiber according to claim 1 is wound into a coil and modularized. 15. When a dispersion compensation amount at a wavelength of 1550 nm is −640 ps / nm, a wavelength band of 1535 is set.
The dispersion compensation module according to claim 14, wherein a total loss is 7 dB or less in a wavelength range from nm to 1565 nm. 16. A wavelength band of 1535 nm to 1610 nm
16. The dispersion compensation module according to claim 15, wherein the total loss is 7 dB or less. 17. When the dispersion compensation amount at a wavelength of 1550 nm is −320 ps / nm, a wavelength band of 1535 is used.
The dispersion compensation module according to claim 14, wherein a total loss is 3 dB or less in a wavelength range of from 1 nm to 1565 nm. 18. A wavelength band of 1535 nm to 1610 nm
18. The dispersion compensation module according to claim 17, wherein the total loss is 3 dB or less. 19. At a wavelength of 1550 nm, the chromatic dispersion D _DCF is -40 ps / nm / km or less, and the ratio (S _DCF / D _DCF ) of the chromatic dispersion D _DCF to the dispersion slope S _DCF is 0.005 / nm or more. And the effective area is 20 μm ²
A dispersion compensating optical fiber characterized by the above. 20. At a wavelength of 1550 nm, the chromatic dispersion D _DCF is -40 ps / nm / km or less, and the ratio (S _DCF / D _DCF ) between the chromatic dispersion D _DCF and the dispersion slope S _DCF is 0.005 / nm or more. And the transmission loss is 0.5 dB /
km or less.