JPS5913644A - Manufacture of optical fiber retaining plane of polarization - Google Patents

Abstract

PURPOSE:To manufacture the titled optical fiber free from central slip at the core and having a sufficient ellipticity, by deforming a quartz tube having a film for cladding to a tube having an elliptical cross-section, forming a base material by a rod-in-tube system by using the deformed tube, and drawing the base material. CONSTITUTION:A film 2 of lower m.p. glass such as B2O3+SiO2 glass for outer cladding is formed on the inner wall of a quartz tube 1, and the tube 1 is deformed to an elliptical tube 4 having 15-40% ellipticity by heating while evacuating the tube 1. A film 5 of higher m.p. glass such as high purity SiO2 glass for inner cladding is formed on the outside of a rod 6 for a core, the rod 6 is put in the elliptical quartz glass tube 4 having the film 2, and they are united in a body by heating while evacuating the tube 4 in accordance with the desired ellipticity. The resulting base material is drawn to obtain an optical fiber retaining the plane of polarization. The ellipticity of the outer clad of the fiber is >=40%.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a polarization maintaining optical fiber.

About polarization maintaining optical fiber 1. L, JP-A-56-9
In Publication No. 9306 and Japanese Unexamined Patent Publication No. 57-3730B, the 7.4 pole-and-line 4M construction was disclosed in SuC.
3. Although detailed explanations of the functions of A and the like are omitted here, the functions of a3 and c1si J in this invention are the first.
If/i structure as shown in the figure, 11 is called a quartz jacket, 12 is called an I side side, 15 is called an inner cladding, and 16 is called a core.

A relatively reliable method for obtaining such a structure is disclosed in Japanese Patent Application Publication No. 2003-125222. Among them, there is the J CV D method as disclosed in the R publication.

By the way, when Jζ-C is manufactured using the above-mentioned inner ft CV D method, a second layer is placed in the center of the produced light) 71 ipa.
A center coloring phenomenon occurs as shown in Figures (a) and (b). This part corresponds to the middle heat of the core and plays an important role in light transmission, so it is necessary to avoid this phenomenon as much as possible.

A core rod without a center is manufactured using the sol-gel method, etc., and then exposed to light using the ) 7 There is a /j method for manufacturing fibers.

In fact, it is not possible to simply apply this method in the manufacture of polarization maintaining optical fibers that include layers with an elliptical cross section.

In order to obtain a predetermined bond length, it is essential to adjust the predetermined ellipticity to −(1q), and in the internal CVD method described above, J and However, with the rod-in-build method (
, 1. It is not necessarily possible to control the ellipticity uniquely depending on the relationship between the composition of the j lath and the woven material.

The reason for this [I think it will be gradually elucidated through research by Shun Yoima and will go to C] is that a film (4 + 1" rad is inserted into a cylindrical glass tube, heated while reducing pressure, and becomes solid. It is difficult to obtain the desired polarization preserving optical waveform.
It's impossible.

Furthermore, my NJ sword last ↑1 with an ellipticity of 5%! ! +! 7
A cylindrical core rod is inserted into it, and it is heated without being depressurized to make it solid. C is also a polarization-maintaining light beam with an ellipticity of b%), but the ellipticity must be controlled by reducing the pressure m. Haha, that's totally impossible. However, the generally required ellipticity of a polarization maintaining optical fiber is /1.0% or more.

In view of the above situation, the present invention aims to provide a method for producing a polarization-maintaining optical beam that has no center point in one horn and can have a desired ellipticity of 1rl by controlling the amount of pressure reduction. Dozu-ru.

The structure of the present invention will be specifically explained based on one embodiment with reference to the drawings.

In Figure 3, C, 1 has Ishiyata sis'i'X"-",
For example, outer diameter 18 mm M wall thickness 1. bmm degree 0 thing C
There is.

On the inner wall of this quartz glass tube 1, a low melting force glass film 2 with cracks 1 to 1 on the side 1 is formed.

This low melting film strength lath film 2 is B203-l Si 02 based glass or B2O3, [-11) 20s, Qe 02
The layer contains dopants such as 241i or more, and is structured so that the melting point of C is lower than that of other layers. The thickness of this film is about 5, for example, 200 μm.

The inside of the quartz glass tube 3 is depressurized and heated to form an elliptical tube with an ellipticity of 15%.

After A, this elliptical membrane ('J fi English crow tube/I is vertically
” Go offshore from Tsu 1 to G.

] i' I-Jt 6 is a lot manufactured by method C such as VAD payment with no center coating [Yes, for example, outer diameter 700μ
It has a thickness of about 7n C' and is coated in advance with a high melting point tunoras film 5 which becomes the inner cladding.

The high melting point glass film 5 is high purity SiO2 containing high purity 5iO2L)L, < is "", and the low melting point glass film 2
However, it does not need to have a higher melting point than the quartz glass tube 1 or the core rod 6.

In the state shown in FIG. 1, the base material is heated and integrated while reducing the pressure according to the desired ellipticity.

In this way, by setting the quartz glass pipe 3 to 15% ellipticity in advance and performing the rod inch lubricant, it is easy to control the amount of pressure reduction to create a base material with a circularity of 40% or more. 1q. (Although it is possible to make the ellipticity of the base material 40% or more, it is practically unnecessary.) In drawing the base material obtained in this way, , a polarization-maintaining optical fiber having a predetermined ellipticity can be easily obtained.

Furthermore, the invention further ellipsoidizes the film-coated quartz glass tube 3 to form an ellipsoidal film 4 with an ellipticity of 20%, and similarly inserts the covered quartz glass tube 3 (=J core lot G). Then, the mixture was heated under reduced pressure to obtain a base material.

In this case as well, it was possible to easily obtain a base material with an ellipticity of 40% or more.

To give an example, an elliptical membrane-coated quartz glass tube 4 with an ellipticity of 20% and an inner diameter of 2 mm is formed, a coated core rod 6 with an outer diameter of 700 μmm is inserted, and the inner pressure is reduced to -20 mm while standing vertically. - I20 and heated to obtain No. 1 material. A polarization-maintaining optical fiber obtained by drawing this base material had an ellipticity of /lO%C and a coupling length of /l mm r at a wavelength of 0.63 μmm.

The normally required ellipticity of polarization maintaining optical fiber is 40%.
Because of the above, the range of the ellipticity of the quartz glass tube 4 is 1! l)% to /IO%, more preferably IJ 20% to /IO%.

The ellipticity used in this specification refers to the ellipticity of the outer shape of the polarization-maintaining optical fiber and its base material (in other words, the outer cladding 12). 4. Smell (refers to the ellipticity of its external shape.

If the method of preparing this defense as explained above is used, the following remarkable effects will be produced.

(1) A is manufactured by the rod inch cope method without forming any part of the J CV D method.
There is no center ().

(2) Membrane f size quartz glass tube to ellipticity 15%・40
By controlling the amount of pressure reduction during solid integration, it is easy to achieve an ellipticity of 40%.
The above polarization maintaining optical fiber can be obtained.

(3) The high melting point glass film that becomes the inner cladding is not coated in advance on the two rods, and is formed on the inner wall of the low melting point glass film by the internal angle CV method. The selection range of the film composition can be expanded to a particularly low melting point, and an 11-wavefront preserving optical fiber with a large ellipticity can be easily obtained.

[Brief explanation of the drawing]

Figure 1 shows the polarization-maintaining light produced by the present invention.
Cross-sectional explanatory diagrams showing the fiber, Figures 2 (A) and (D) are line diagrams showing the refractive index distribution to explain the centerless () phenomenon, Figures 3 and 4 (31 One implementation of the present invention It is an explanatory diagram of J cross section showing an example. 1: Quartz glass tube, 2: Low melting point glass film, 3: Film q7
-I English glass tube, 4: Oval membrane A"115 English glass tube, 5: High melting point glass membrane, 6: Core rod.

Claims (1)

[Claims] 1? 1. A low melting point glass film 2 serving as an outer cladding is formed on the inner wall of the Ei quartz glass tube 1, and the inside of the quartz glass tube 3 is depressurized and heated. Cross section has an ellipticity of 15% to 4
A core rod 6 coated with a high melting point glass film 5 serving as an internal cladding is inserted into the elliptical quartz tube 4, and is integrated by reducing pressure and heating. A method for producing a polarization-maintaining optical fiber 2, characterized in that the obtained polarization-maintaining optical fiber is delineated to obtain a polarization-maintaining optical fiber whose outer cladding has an ellipticity of /IO% or more. Melting point glass film 2 is 13203
2. The method for producing a polarization-maintaining optical fiber according to claim 1, wherein the optical fiber is a glass fiber containing: 3 The high melting point glass film 3 that becomes the inner crat is l3203
2. The method for manufacturing a polarization-maintaining optical fiber according to claim 1, wherein the fiber is made of glass that does not contain.