JPS60201305A - Polarization conservative optical fiber and its manufacture - Google Patents

Abstract

PURPOSE:To facilitate work and to prevent unnecessary residual stress from being generated by composing the optical fiber of a core made of a quartz rod having a higher refractive index than a jacket and a refractive index adjusting part surrounded with a stress inducing member. CONSTITUTION:The optical fiber consists of the jacket 10 with a refractive index n10, core 11 as an optical propagation path which is made of the quartz rod having the higher refractive index n11 than the refractive index n10, stress inducing member 12 with a refractive index n12, and refractive index adjusting part 13 with a refractive index n13 other than the core 11 and stress inducing member 12 in the jacket 10. Consequently, the stress inducing member 12 gives stress anisotropy to the core 11 to obtain birefringence. Further, the stress inducing member 12 with the refractive index n12 is present in the (x) direction of the core 11 with the refractive index n11, and the refractive index adjusting part 13 with the refractive index n13 is present at the part surrounded with the internal surface of the jacket 10, core 11, and stress inducing member 12 in the (y) direction of the core 11. Consequently, the refractive index of the periphery of the core 11 has anisotropy, and consequently birefringence is obtained as well.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a polarization maintaining optical fiber and a method for manufacturing the same.

(Conventional Comparison i) FIGS. 1A to 1C are cross-sectional views of structural examples of conventional polarization-maintaining optical fibers. In each of the optical fibers shown in these figures, stress is applied to the core and birefringence is imparted to the core, thereby causing the optical fiber to maintain single polarization. FIGS. 1A and 1B are structural cross-sectional views of elliptical clad and panda-shaped stressed single-polarization maintaining optical fibers, respectively. Among these polarization-maintaining optical fibers, the one shown in FIG. 1(A) has a core 1 with a refractive index of nl and a perfectly circular cross section, and a cladding 2 with a refractive index of n2 and an elliptical cross section. , a jacket 3 whose cross section is a perfect circle as a stress f1 applying member, and a B2O3 dope having a large coefficient of thermal expansion is used for the cladding 2, and the shape of the cladding 2 is made into an ellipse.
The birefringence is obtained by imparting stress anisotropy to. However, in an optical fiber with such a structure, the cladding 2 is
There is a difficulty in processing the cross section into an elliptical shape. The one shown in FIG. 1(B) is a B20 consisting of a core 4 with a refractive index of n and a stress applying member inserted into a hole drilled with a glass lathe.
．． It has a pair of doped stress applying parts 5 and a cladding 6 with a refractive index of n2, and in the same manner as described above, stress anisotropy is imparted to the core 4 to obtain the birefringence. The fabrication process for structured optical fibers is complicated. Figure 1 (C)
1 is a structural cross-sectional view of a non-axisymmetric single polarization maintaining optical fiber. The one in FIG. 1(C) has a core 7 with a refractive index of 111.
and a pit 8 formed of air or liquid with a low refractive index,
The core 7 has a cladding 9 with a refractive index of 12, and the pits 8 provide an extraordinary birefringence +J1, but there is a difficulty in processing the core 7. As described above, all of the conventional examples have difficulties in processing, and as a result, their manufacturing costs are high. In addition, stress is applied by drilling holes or doping with 8205, etc., and the residual stress caused by this stress application generates a photoelastic effect and gives birefringence, but unnecessary residual Since the structure makes it difficult to release stress, this unnecessary residual stress has a rather unfavorable effect on the light propagation characteristics of the optical fiber.

(Objective) The present invention has been made in view of the above-mentioned problems, and it is possible to reduce manufacturing costs by facilitating processing, and to improve light propagation characteristics by preventing unnecessary residual stress from occurring. The purpose of this research is to provide an excellent polarization maintaining optical fiber.

(Structure) FIG. 2 is a structural sectional view of a polarization-maintaining optical fiber according to an embodiment of the present invention. The optical fiber of the embodiment shown in FIG.
0 refractive index 11. . A core 11 that is made of a quartz rod having a higher refractive index of 11 (+ (However, this refractive index of 11.1 decreases continuously in the direction of the radius r) and serves as a light propagation path, and the core A core 11 and a jacket 10 are arranged on both sides of the core 11 symmetrically with respect to the central axis of the core 11 .
a stress applying member 12 with a refractive index n12 provided in contact with the inner surface of the core 11 in the jacket 10;
and a refractive index adjusting section 13 having a refractive index n13 other than the stress applying member 12. The refractive index adjusting section 13
is a gas with a low refractive index such as air (refractive index II +
3') or a liquid (refractive index, , , 311). The refractive index, .

In such a configuration, the core 11 is
Not only can stress anisotropy be imparted to the stress anisotropy to impart birefringence to it, but also a stress imparting member 12 having a refractive index n12 is present in the X direction of the core 11 having a refractive index n+1, In addition, in the X direction of the core 11, the refractive index adjustment part 13 with a refractive index of n13 exists in the area surrounded by the inner surface of the core 10, the core 11, and the stress applying member 12, so that the Anisotropy will occur in the surrounding refractive index, which will also cause birefringence. Therefore, in the optical fiber of this embodiment, birefringence occurs in the X direction and the X direction, and the light propagation characteristics within the optical fiber are greatly improved.

Next, the refractive index distribution within the jacket 10 will be explained with reference to FIG. FIG. 3(A) shows the refractive index adjusting section 13.
is the refractive index +13. It shows the refractive index distribution when . In the figure, r(x) on the horizontal axis is a coordinate axis indicating the X direction in FIG. 2 from the center of the core 11, and n on the vertical axis is a coordinate axis indicating the refractive index. FIG. 3(B) shows the refractive index distribution when the refractive index adjusting portion 13 is a gas having a refractive index of n13. FIG. 3(C) shows that the refractive index adjustment section 13 has a refractive index of
It shows the refractive index distribution when it is a liquid of I.

Therefore, in the optical fiber of this embodiment, since the core 11 and the stress applying member 12 are simply placed inside the jacket 10, there is no need for drilling as in the conventional example.
Moreover, the above-mentioned unnecessary residual stress can be removed by being released from the refractive index adjustment section 13 made of gas, liquid, or the like. Therefore, the optical fiber in this embodiment can be easily processed and has excellent light propagation characteristics.

In addition, although the refractive index of the core 11 in the above embodiment was changed continuously, it can be implemented in the same way even if it is changed stepwise. Also, core 1
1 and the stress applying member 12 do not necessarily have to be circular.

The optical fiber having the above configuration is manufactured by the following procedure.

That is, as shown in FIG. 4, after heating and fusing at least a portion of the core base material 21 and the stress-applying base materials 22 disposed on both sides of the core base material 21, the core base material 21 is heated and fused. 21 and the stress-applying base material 22 are inserted into the jacket tube 20 in at least a part of the combination base material formed by inserting the stress-applying base material 2 into the jacket tube 20 and the stress-applying base material 2 inscribed therein.
2 is heated and fused to form a starting base material 24, and the starting base material 2
4 to form an optical fiber. The refractive index adjusting section 13 surrounded by the inner surface of the optical fiber jacket 10, the core 11, and the stress applying section 12 formed in this manner may be left as a space or may be filled with a material having a refractive index of 1 to 1.6 as necessary. Fill. As a method for heat-sealing the core base material 21 and the stress-applying base material 22 and the stress-applying base material 22 and the jacket quartz tube 20, for example, one end is gripped using a glass lathe, and a burner or the like is used. All you have to do is heat the area to be fused.

(Effects) As described above, according to the present invention, there is a jacket, a core made of a quartz rod that is provided concentrically with the jacket and has a higher refractive index than the jacket, and It consists of a stress-applying member provided symmetrically on both sides thereof so as to be in contact with the jacket 7 and the jacket F, respectively, the inner surface of the jacket, and a refractive index adjusting portion surrounded by the core and the stress-applying member. There is no need for drilling, elliptical processing, etc., and unnecessary residual stress is not generated by the refractive index adjustment section, etc., making processing easier and making it possible to obtain optical fibers with excellent light propagation characteristics. It became.

[Brief explanation of the drawing]

FIG. 1 (A), (B), and (C') show the conventional polarization-maintaining light 7.
FIG. 2 is a structural cross-sectional view of the fiber, and FIG. 3 is a structural cross-sectional view of a polarization-maintaining optical fiber according to an embodiment of the present invention.
C) is a diagram showing each refractive index distribution when the refractive index adjustment part of the optical fiber in FIG. 2 is other than gas or liquid, when it is gas, and when it is liquid. FIG. 10 is a jacket, 11 is a core, 12 is a stress applying part,'
13 is a refractive index adjusting section, and 24 is a starting base material. Applicant Tuck Electric Cable Co., Ltd. Agent Patent Attorney Kazuhide Okada 1st Section A) Figure 1 (C) Figure 3 IGA) Written Amendment to Procedures (Voluntary) May 21, 1980 Commissioner of the Patent Office Polarization Preserved light 7T fiber and its manufacturing method 3 Relationship with the person making the amendment 1f Representative of the patent applicant Ken Yu Oishi 6 11) Number of inventions increased by the amendment None 7 Subject of the amendment (1) Inventions in the specification Contents of amendments in the detailed explanation column (1) Specification (a) Page 2, line 15, 1 These figures” should be changed to [t
Correct as J%1Figure (A) CB) J. (b) From page 2, line 18, 1, figure 1...” to page 2
Correct the [... panda-shaped up to 1 in line 0 as follows. [Figure 1 (A) is an elliptical clad type, Figure 1 (B) is a bang type.'' (c) In the 4th line of page 5, [this jacket) 1 (IOJ] is replaced with ``this jacket) 10''. and correct it. (d) On page 5, pages 6-7, “This refractive index...
It is... "For example, in the case of a graded index core, this refractive index nl+ decreases continuously in the radial Y direction. ] and correct it. (E) The text from [and...] on page 5, line 16 to the end of line 20 of the same page is corrected as follows. It is preferable that the refractive index n13 in the Y direction satisfies the following formula. nz(r) is the refractive index at a distance from the center of the core. In the case of a system fiber, the maximum value of nzM is about 1.4 to 1.6, so n
zz must be less than or equal to that value. ” (to) Page 6, line 13, 1 Figure 3 (A>... Correct everything from what to the end of the second line of the next page as follows. [Figure 3 (A) shows the stress applied The figure shows the refractive index distribution when the portion 12 has a refractive index n12.In the figure, r(x
) is a coordinate axis indicating the X direction in FIG. 2 from the center of the core 11, and n on the vertical axis is a coordinate axis indicating the refractive index. Figure 3 (
In B), the refractive index adjusting section 13 has a refractive index n13 like that of air.
It shows the refractive index distribution in the Y direction when the gas is small. FIG. 3(C) shows a preferred embodiment, and the refractive index in the Y direction when the refractive index adjusting section 1 13 is a material having a refractive index, It, that satisfies the formula (1). It shows the distribution. ] (2) Drawings (a) Figure 3 (A), (B), and (C) will be corrected as shown in the attached drawings. Above Figure 3 (A) Figure 3 (B) Figure 3 (C) 1-→D (Y)

Claims (5)

[Claims] (1) A jacket, a core made of a quartz rod that is provided concentrically with the jacket and has a higher refractive index than the jacket, and a core and a jacket on both sides of the core symmetrically with respect to the central axis of the core. 1. A polarization-maintaining optical fiber comprising: a stress applying member provided in contact with the inner surface of the jacket, a core, and a refractive index adjustment section surrounded by the stress applying member. (2) The polarization-maintaining optical fiber according to claim 1, wherein the # assigned refractive index adjusting portion is made of a material having a refractive index of 1 to 1.6. (3) The polarization-maintaining optical fiber according to claim 1, wherein the refractive index adjusting section is a gas. (4) The polarization maintaining optical fiber according to claim 1, wherein the refractive index adjustment section is a liquid. (5) After heating and fusing at least a portion of the core base material and the stress-applying base materials arranged on both sides of the core base material, the core base material and the stress-applying base material are bonded together for the jacket. A small part of the combined base material inserted into the tube (in both parts, the jacket tube and the stress applying base material inscribed therein are heated and fused to form a starting base material, and the starting base material is used to form an optical fiber. A method for manufacturing a polarization-maintaining optical 7 fiber, characterized by drawing a line into a polarization-maintaining optical fiber.