JPH0216508A - Optical fiber coupler and production thereof - Google Patents

Abstract

PURPOSE:To obtain the optical fiber coupler having a low loss and an excellent temp. characteristic by constituting said coupler of a full coating-removed part where the coating of the optical fiber is removed fully over a prescribed length and a half coating-removed part where one side of the coatings on both sides is removed over a prescribed length. CONSTITUTION:The coating-removed part 15 consisting of the full coating- removed part 13 and the half coating-removed part 14 is constituted to the optical fiber 16. The optical fiber coupler 11 can, therefore, be constituted without generating a bend of a small radius of curvature in a base optical fiber 17. The generation of a small bend in the radius of curvature of the bare optical fiber 17 is obviated and the deterioration of performance by a temp. change is not generated. The temp. characteristic of the optical fiber coupler is improved in this way.

Description

Detailed Description of the Invention [Industrial Field of Application J This invention relates to an optical fiber coupler that is used not only for branching optical signals in an optical fiber communication system but also for optical fiber sensors and the like. This is a related story.

"Prior Art" FIG. 5 is a diagram showing an example of a conventional optical fiber coupler, and reference numeral 1 indicates the optical fiber coupler.

This optical fiber coupler 1 includes a bare optical fiber 2 and a coating 3.
The optical fibers exposed from the coated removed portions 5 formed on each of the two or more optical fibers 4 subjected to ! l! line 2
The fused portion 6 is formed by fusion-stretching.

As a method for forming this fused portion 6, first, a predetermined length of a part of the coating 3 of the optical fiber is removed, and two optical fibers 4 with bare optical fibers 2 exposed are prepared as shown in FIG. like,
The positions of the respective coating removed portions 5 are aligned and overlapped.

Next, as shown in FIG. A fixing part 7 is formed to bind each bare optical fiber 2 using adhesive or thread so that the center portions of the HQ2 overlap.

Then, as shown in FIG. 8, the optical fiber i! between these fixing parts 7.7 is connected. The l wire 2.2 is heated with a high temperature heating source 8 such as an oxyhydrogen flame to fuse the two bare optical fibers 2 together,
Further, each optical fiber 4 is separated and stretched to form a fused portion 6. The stretching ratio of the fused portion 6 is adjusted as appropriate so that the manufactured optical fiber coupler l has a predetermined branching ratio.

The optical fiber coupler 1 configured in this manner can perform optical coupling such as branching of transmitted light and merging of light at the fused portion 6 where the two bare optical fibers 43a2 are fused and stretched.

"Problem to be Solved by the Invention" However, in such a conventional optical fiber coupler, the fixed part 7 and the coated removed part 5 of the bare optical fiber 2 are
There is a problem in that bends with a small radius of curvature occur at the end portions of the optical fiber couplers or in their vicinity, resulting in deterioration of excess loss characteristics, which is one of the important characteristics of optical fiber couplers.

In addition, there was a problem in that the bending that occurs in the bare optical fiber 2 makes the optical fiber coupler 1 mechanically unstable against temperature changes, leading to deterioration of temperature characteristics.

The present invention was made in view of the above circumstances, and an object thereof is to provide an optical fiber coupler with low loss and excellent temperature characteristics.

[Means for Solving the Problems] As a means for achieving the above-mentioned [1], the optical fiber coupler according to the present invention includes two or more optical fibers in which a part of the coating of the coated optical fiber is formed with a coating removed portion. An optical fiber coupler in which a fused portion is formed by overlapping each other and fusion-stretching each bare optical fiber from the portion where the coating is removed,
The above-mentioned coating removed portion is composed of a fully coated removed portion where a predetermined length of the entire coating of the optical fiber is removed, and a half coated portion where only one side of the coating on both sides is removed for a predetermined length.

In addition, as a method for manufacturing an optical fiber coupler configured in this way, two or more optical fibers each having a coating layer are coated with a completely removed portion where a predetermined length of the coating of the optical fiber is removed, and a portion where the coating is completely removed. Forming a covering removed part consisting of a half-removed part where one side of the covering on both sides is removed by a predetermined length,
Next, it is preferable to overlap the bare optical fibers exposed from the removed portions of the respective optical fibers, and then fuse and stretch the overlapped bare optical fibers to form a fused portion.

"Operation" The part where the coating of the optical fiber is removed is composed of a completely removed part where the entire coating of the optical fiber is removed for a predetermined length, and a half-covered part where only one side of the coating on both sides is removed for a predetermined length. However, by overlapping the coated portions of two or more optical fibers, bends with a small radius of curvature will not occur in the bare optical fibers.

In addition, two or more optical fibers having the above-mentioned coat removed portions are stacked with the bare optical fibers exposed from each coat removed portion, and then the overlapped bare optical fibers are fused and stretched to form the fused portion. By forming this, it is possible to manufacture an optical fiber coupler without bending the bare optical fiber with a small radius of curvature.

"Embodiment" The first CQG is a diagram showing an embodiment of the invention described in claim 1, and reference numeral II is an optical fiber coupler.

This optical fiber coupler 11 has a coating I2 for light) γ
A coating removed portion 14, which is formed by removing a predetermined length of only one side of the coating I2 on both sides, is formed on a part of the fiber. 15 are superimposed, and each bare optical fiber I7 exposed from the completely removed portion 13 is fused and stretched to form a fused portion I8. .

The coating half removed portion 14 is the coating 12 of the optical fiber 1G.
A parallel removed portion where half of one side of is removed and each bare optical fiber 17 overlaps within the coating 12! 9 and a tapered surface portion 20 in which a tapered surface is formed by gradually increasing the coating 12 from the parallel removed portion 19 to a state where the coating 12 is not removed.

Further, in the vicinity of both ends of the two overlapping bare optical fibers 17 exposed from the completely removed portion 13, there are fixing parts 21 in which each bare optical fiber 17 is fixed using adhesive or thread. It is provided.

'' As the bipedal optical fiber 16, various optical fibers can be used, such as a single-mode optical fiber, a multi-mode optical fiber, or a stress-applied polarization-maintaining optical fiber made of silica glass, multicomponent glass, etc. Optical fiber wires or cored optical fibers, which are such bare optical fibers coated with one or more layers of synthetic resin such as silicone resin or nylon, are used.

In the optical fiber coupler 1■, the bare optical fibers 17 of each of the two optical fibers 16 are fused and stretched at the fusion part 18, where optical coupling such as branching of transmitted light and merging of light is performed. be able to.

In this way, 11 optical fiber couplers were grown! The coating is removed from the fully-removed portion 13 of the optical fiber 16 in which a predetermined length of the covering 12 of the optical fiber 16 is removed, and the half-removed portion 14 of which a predetermined length of only one side of the coating 12 on both sides is removed. Since the portion 15 is formed, the bare optical fiber 17 of each of the two optical fibers 16 is the parallel removed portion of the fully coated portion 13 and the partially coated portion I4. 9, and are gradually separated from the parallel removal section 19 at the tapered surface section 20, and the two optical fibers 16 are separated from the terminal end of the tapered surface section 20.
Divided into.

Therefore, bending with a small radius of curvature does not occur in the bare optical fiber I7, and the optical fiber coupler 11 can have a low loss.

In addition, the optical fiber coupler 1! does not bend with a small radius of curvature in the bare optical fiber I7 and does not deteriorate in performance due to temperature changes. temperature characteristics can be improved.

Further, since the bare optical fiber 17 is not bent with a small radius of curvature, the dimension of the fused portion I8 can be shortened in the length direction.

In the previous example, the half-covered portion I4 was composed of the parallel removed portion and the tapered surface portion 20, but only one of these can be used as the half-covered portion! 4 may be configured.

Furthermore, in the previous example, the configuration was made using two optical fibers I6, but for example, by arranging a plurality of optical fibers 16 in the horizontal direction to form an array type coupler hv1, two or more optical fibers can be used. 16 may be used to configure an optical fiber coupler.

Next, the invention set forth in claim 2 will be explained in detail.

FIGS. 2 to 4 are for explaining the invention set forth in claim 2 in detail.

To manufacture the optical fiber coupler II according to this example, first, a part of the coating 12 of the optical fiber is removed to form a removed portion I5, and the bare optical fiber 17 is removed as shown in FIG. An optical fiber 16 with a portion exposed is produced.

This coating removal portion 15 is a coating I2 as shown in FIG.
A fully covered part 13 in which a predetermined length of the entire part of the covering 12 is removed, and a half covered part I4 in which a predetermined length of only one side of the covering 12 on both sides of the covered part 12 is removed are provided.
Reference numeral 4 includes a parallel removed portion I9 in which half of one side of the coating 12 of the optical fiber 16 is removed, and a tapered surface portion 20 in which the coating 12 gradually increases from the parallel removed portion I9.

Next, the coat-removed portions 15 of the two optical fibers I6 having the coat-removed portions I5 are superimposed, and the two bare optical fibers exposed from the coat-removed portions 13 are then stacked together as shown in FIG. A fixing part 21 is formed near both sides of I7 by binding these bare optical fibers 17 with adhesive or thread.

At this time, the bare optical fiber 17 of each optical fiber I6
overlaps the parallel removed portion 19 of the completely removed portion 13 and the partially removed portion 14, gradually separates from the parallel removed portion 19 at the tapered surface portion 20, and from the end of the tapered surface portion 20 two beams of light are formed. This results in a state where the fibers are divided into 16 fibers.

Next, the space between the fixing parts 21 is heated and fused using a high temperature heating source 22 such as an oxyhydrogen flame, and then stretched as shown in FIG. 4 to form a fused part I8. The stretching ratio of this fused portion 8 is the same as the optical fiber coupler to be manufactured! is adjusted as appropriate so that it becomes a predetermined branching ratio.

Through the above operations, the optical fiber coupler 11 having a configuration not shown in FIG. 1 is manufactured.

In the manufacturing method according to this example, the coating removed portion consists of a fully covered portion 13 in which the entire predetermined length of the coating 12 is removed, and a half covered portion 14 in which only one side of the coating I2 on both sides is removed by a predetermined length. Two optical fibers 1 forming 15
6, the bare optical fiber exposed from each coat removed portion 15! 7 are overlapped, and then the overlapped bare optical fibers 17 are fused and drawn to form a fused portion 18, thereby producing an optical fiber coupler 11 with a small radius of curvature and no bending in the bare optical fiber 7. Therefore, it is possible to obtain a high performance optical fiber coupler 11 with low loss and excellent temperature characteristics.

(Manufacturing example) Core diameter 8μm, cladding diameter 125μm, relative refractive index difference 0.
An optical fiber coupler having the same structure as that shown in FIG. 1 was prepared using an optical fiber having a coating diameter of 3%, a coating diameter of 400 μl, a working wavelength of 1.30 #m, and a cutoff wavelength of 1.28 μm.

Using the obtained optical fiber coupler, the temperature was varied from -20°C to +60°C, and the variation in excess loss was measured. As a result, it was confirmed that the fluctuation range was as low as 0.05 dB, and excellent temperature characteristics were obtained.

On the other hand, a conventional optical fiber coupler shown in FIG. 4 was manufactured using the same optical fiber as the previous one, and the variation in excess loss was measured by varying the temperature in the same manner as in the above-mentioned optical fiber coupler. As a result, the fluctuation range of conventional optical fiber couplers is 0.
．． It was 0.02 dB.

"Effects of the Invention" As explained above, the optical fiber coupler according to the invention as set forth in claim 1 has a coating removed part in the optical fiber consisting of a fully coated removed part and a half coated part. An optical fiber coupler can be constructed without bending the bare fiber with a small radius of curvature, and the loss of the optical fiber coupler can be significantly reduced.

Further, since bends with a small radius of curvature do not occur in the bare optical fiber, and the performance does not deteriorate due to temperature changes, the temperature characteristics of the optical fiber coupler can be improved.

Furthermore, since bends with a small radius of curvature do not occur in the bare optical fiber, the dimensions of the fused portion can be shortened in the length direction.

Further, in the method for manufacturing an optical fiber coupler according to claim 2, two optical fibers each having a coat-removed portion formed with the above-mentioned fully coated portion and a partially coated portion are exposed from each coat-removed portion. By overlapping the optical fibers and then fusion-stretching the overlapping bare optical fibers to form a fused part, the optical fibers can be bent without bending the optical fibers with a small radius of curvature. Since a fiber coupler can be manufactured, an optical fiber coupler with low loss and excellent temperature characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a side view of an optical fiber coupler showing one embodiment of the invention as claimed in claim 1, and FIGS. 2 to 4 are claims 2.
FIG. 2 is a side view of the optical fiber after the coating is removed, and FIG.
The figure is a side view showing a state in which two optical fibers are overlapped, FIG. 4 is a side view showing a state in which a fused portion is formed, FIG. 5 is a side view showing a conventional optical fiber coupler, and FIGS. 8th
The figure is a side view for explaining the manufacturing method of the optical fiber coupler shown in FIG. 5 in order of steps. II...Optical fiber coupler 12...Coating wire 3...Coating completely removed portion 14...Coating half removed portion...Coating removed portion...Optical fiber...Optical fiber bare wire... Fusion part.

Claims (2)

[Claims] (1) Two or more optical fibers with a coating removed part formed on a part of the coating of the coated optical fiber are overlapped, and the bare optical fibers exposed from the coating removed part are fused and stretched to fuse them. In the optical fiber coupler formed by forming a bonding part, the coating removed part includes a completely removed part in which a predetermined length of the optical fiber's coating is removed, and a predetermined length in which only one side of the coating on both sides of the optical fiber is removed. An optical fiber coupler comprising a semi-removed portion. (2) For two or more coated optical fibers, there is a fully-removed portion where a predetermined length of the optical fiber's sheath is removed, and a half-remove portion where a predetermined length of only one side of the sheath on both sides of the optical fiber is removed. Then, the bare optical fibers exposed from the coated removed parts of each optical fiber are overlapped, and then the overlapped bare optical fibers are fused and stretched to form a fused part. A method of manufacturing an optical fiber coupler, characterized in that: