JPS6011250A - Fiber for optical transmission and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a single-mode fiber for optical transmission with no absorption loss by heating a porous aggregate of fine particles consisting of an SiO2 core contg. GeO2 and an SiO2 clad in an atmosphere contg. F and by carrying out drawing. CONSTITUTION:Fine particles for a core 3 and a clad 4 are deposited at once on a rotating rod in the axial direction with plural burners 1, 2 to manufacture a porous base material consisting of an SiO2-GeO2 glass core and an SiO2 clad by a flame hydrolysis method. The base material is made transparent by heating at about 1,500 deg.C in an atmosphere of He+Cl+SF6 in an electric furnace. The size of the base material is about 45phiX200mm.. Fluorine can be well infiltrated into the clad and core while the base material is in a porous state. The transparent base material is drawn to 10mm.phi, coated with a pure quartz pipe as a jacket, and drawn to obtain a fiber of 125mum outside diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a fiber for single mode optical transmission using the VAD method and a method for manufacturing the same.

[Background technology]

The single mode optical transmission fiber using the conventional VAD method is
As shown in Fig. 1, a fine particle aggregate (porous base material) consisting of a core 3 and a cladding 4 is formed by a plurality of burners 1.2.
GeC14 is made by a process of simultaneously depositing GeC14 in the rotating axial direction, then turning it into transparent vitrification in a He atmosphere containing chlorine gas, stretching it, covering it with a quartz pipe, and drawing it. as raw material, 5rC for cladding
As a result, the resulting glass composition has a core of S+C12GeO2 and a cladding of S+02, with a refractive index distribution as shown in FIG. On the other hand, in recent years, a structure as shown in FIG. 3 has been proposed as a new refractive index distribution structure for a fiber for single mode optical transmission. (The Be1l SystemTe
chnicalJournal VoC61, A2.
(See pages 262-266, 1982) As shown in Figure 4, the glass composition of the fiber according to this proposal is that the core is GeO3-S i02 and the cladding is S.
102-F-P2O5, and the manufacturing method is M
It is based on the CVD method.

In the structure shown in Fig. 4, the core glass composition is made of 5i02GeO2, but this glass composition is unstable in terms of glass structure, which causes absorption due to defects appearing in the ultraviolet absorption spectrum. peaks and radiation,
It is clear from the coloring etc.

It goes without saying that defects in the glass structure have a negative effect even in the near-infrared wavelength band in which optical transmission fibers are used.

Next, the presence or absence of addition of P2O5 in the composition of the cladding will be described. In the conventional MCVD method, in order to avoid manufacturing difficulties such as shrinkage of quartz tubes due to high temperatures, it was essential to add P2O, which provides physical properties of low viscosity.

However, P2O5 is unnecessary from an optical point of view, and on the contrary, a P atom with a coordination number of 5 is unstable in a glass structure and is said to be unfavorable optically.

[Disclosure of the invention]

Based on the viewpoints explained above, the present invention is an optical transmission unit with a novel structure in which the core contains G e O2 and F and the cladding contains only F without adding P2O5, with the refractive index distribution shown in FIG. The purpose is to provide a one-mode fiber and a method for manufacturing the same, and as shown in FIG.
One of the characteristics is that the composition of SiO3 and cladding is S+02F, and F is contained in the SiO3, core, and cladding.

In addition to loss, a single mode fiber has dispersion as a characteristic, and shortening the ultraviolet absorption edge tends to bring about favorable results in dispersion characteristics as well.

Currently, the most commonly used wavelength in optical communication systems is 1.
．． At 3 μm, the total dispersion of a single mode fiber at this wavelength is the refractive index profile shown in Figures 2 and 3.

In the case of , it is known that the value is finite, and the wavelength at which the total dispersion becomes zero is longer than 1.3 μm.

The total dispersion of a single mode fiber is determined by the sum of the material dispersion and the structural dispersion, and the material dispersion is unique to the glass composition due to the wavelength dependence of the refractive index of 1, that is, τ. By incorporating F to shorten the ultraviolet absorption edge, -! -! ! -i! l! The reason why the wavelength of -0 becomes shorter than cdλ2 is based on the theoretical basis that the wavelength dependence of absorption and refractive index' are not independent of each other, but are linked by Kramers-Kronig (mathematically known as Hilbert transform). . Therefore, by incorporating F into the core,
The wavelength at which the total dispersion is zero is the actual wavelength used 1, 3
It is closer to μm and the total dispersion of 1.3μ77Z is less. For these reasons, including F together with GeO□ in the core composition is advantageous for both loss and dispersion.

Next, regarding the composition of the cladding, for the reason already mentioned, it does not contain P2O5 and only F is contained in 5io2.

Next, the manufacturing method of the present invention will be explained.

Generally speaking, if F is introduced in the same process as 1siO□ synthesis, highly volatile fluoride gases such as HF and S+F4
The generation of 51o2 suppresses the nucleation of 51o2, reducing the glass formation rate, resulting in a method with extremely low productivity. Therefore, in the present invention, the core is made of 5i02 and GeO2 glass, and the cladding is made of 5i02 and
A porous base material made of i02 was prepared by a flame hydrolysis method, and it was heated in an electric furnace in an atmosphere of \He + C12 + SF6, where He: 101/min.

C12: 50cc/min, SF6 (100c1
00cc7 T transparent glass. At this time, the temperature is about 15
00'C, and the dimensions of the base material are approximately 45φX 200 mm.
Met. In such a porous base material state, the cladding and core were thoroughly infiltrated with F, and the outer diameter was 125μ77Z.
fiber.

For the optical fibers prototyped above, an ultraviolet absorption spectrum test was conducted on the optical fibers whose cores were made of glass composition 5i02GeO2 containing no F and those made of 5i02F GeO2 of the present invention.The results are shown in Figure 6. As can be seen, it is clear that the product according to the present invention has a low absorption rate.

The microscopic mechanism of the stabilization of the glass structure by adding and containing F is not yet clear, but oxides such as SiO2 and GeO2 react with MOx in the glass. 〈It is easy to become 2 and F
This is thought to be caused by the fact that the gas enters the glass as anions instead of oxygen.

Furthermore, the ease with which defects occur due to G e O 2 is also correlated with the radiation resistance characteristics, and it is expected that the radiation resistance characteristics will be improved by incorporating F.

Also, as shown in Figure 7, the refractive index distribution is core.

A decrease of 0.2% in the relative refractive index difference was observed for both the cladding and the cladding. 'fX, the loss of this optical fiber is 0.45 d
B/IAm (1.3μm) and zero dispersion wavelength is 1.30
It was 5 μyn.

〔effect〕

As explained above, by containing G e O2 and F in the core, and by containing only F in the cladding without P2O5, it is possible to create a single mode fiber for optical transmission with low absorption loss. you can get
By performing the transparent vitrification step in a fluorine atmosphere, F can be uniformly contained in the base material forming the core and cladding.

The formation of a porous base material by the VAD method is no different from the conventional process, and only requires a fluorine atmosphere for the transparentization process. Single mode fibers for optical transmission can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a method of manufacturing a porous preform for an optical transmission single-mode fiber using the conventional VAD method. FIG. 2 is a refractive index distribution diagram of a conventional optical fiber. FIG. 3 is a newly proposed refractive index distribution diagram. FIG. 4 is a glass composition diagram of an optical fiber structure corresponding to the distribution diagram of FIG. 3. FIG. 5 is a diagram of the glass composition of the present invention. FIG. 6 shows the ultraviolet absorption spectra of glasses with and without F. FIG. 7 is a refractive index distribution diagram of an embodiment of the present invention. I... Burner for core, 2... Burner for cladding,
3... Porous core part glass, 4... Porous clad part glass. 295 The purity of the drawings (no change in YF) 5 Government 1 drawing 72 drawings Δ Su 3 drawings 4 Δ 1 Sheet 6 drawings 3 liquids t (nm) Procedural amendment for drawing 7 (1K) July 3rd, 1982 Patent issued in 1982, Shinkin Paperback No. 117796 2 Name of Invention Kennan Optical transmission fiber and its manufacturing method 3 Relationship with the person making the amendment Case Patent applicant address 5-15 Kitahama, Higashi-ku, Osaka Address name (218) Sumitomo Electric Industries, Ltd. 6, Specification of the application subject to amendment 7, Attachment to the contents of the amendment, Application, Full text (by type)
Submit all. 7. Commissioner of the Japan Patent Office Kazuo Wakasugi1, Indication of the case, 1982 Patent Application No. 1177982, Name of the invention, Optical transmission fiber and its manufacturing method3, Person making the amendment, Relationship with the case, Address of the patent applicant. 5-15 Kitahama, Higashi-ku, Osaka Name (213)
) Sumitomo Electric Industries, Ltd. Representative President Satoshi Kawakami Department 4, Agent address 7th floor, Shin-Nakajima Building, 1-9-20 Nishinakajima, Yodoyo-ku, Osaka (Telephone: Osaka 304-8803) Name (7085)
) Patent Attorney Hide Aoki Submit the contents of the revised drawings (Figures 1 to 7) on separate sheets.

Claims (1)

[Claims] (+) 5i0 whose core contains both F and G e 02
2. A fiber for optical transmission, characterized in that the cladding is made of 5i02 glass containing F, and further has a jacket of pure silica glass on the outside of the cladding. (2) The core is GeO2'f! A porous fine particle aggregate made of 5102 glass containing c and a cladding made of 5i02 glass is prepared, and the porous fine particle aggregate is heated in an atmosphere containing F to cause the core and cladding to contain F. A method of manufacturing an optical transmission fiber, which comprises finally drawing the fiber.