JPH02123308A - Production of optical fiber coupler - Google Patents

Abstract

PURPOSE:To easily produce the optical fiber coupler of a low loss and high performance by holding plural pieces of optical fibers to be welded in a contact state by means of a holder having grooves to hold plural pieces of the optical fibers, then welding and stretching these optical fibers by heating. CONSTITUTION:Two or more pieces of the optical fibers 11 to be welded are held in the grooves 13 of the holder 12. The respective optical fibers 11 arrayed in the contact state by the holder 12 are welded by heating and are further stretched. The need for fixing the optical fibers 11 by yarn and adhesive agent is, therefore, eliminated and the production process is simplified. There is no need for twisting the optical fibers 11 with each other and the need for a precise device for twisting the fibers is eliminated; in addition, the optical characteristics of the resulted optical fiber coupler are improved. The polarization maintaining optical fiber coupler having the excellent optical characteristics and particularly polarization characteristics and the high performance is easily produced in this way.

Description

Detailed Description of the Invention "Industrial Application Field" This invention is useful for branching an optical signal incident on one optical fiber to another optical fiber boat, or for branching an optical signal incident on two optical fibers. The present invention relates to a method of manufacturing an optical fiber coupler used for coupling.

``Prior Art'' Conventionally, fused and stretched type optical fiber couplers are known as optical fiber couplers used for coupling or branching optical signals.

FIGS. 11 to 16 are diagrams for explaining a conventional method of manufacturing an optical fiber coupler. In order to manufacture a 2-to-2 type optical fiber coupler made up of two optical fibers by the conventional method, first, a predetermined length of the front 12 of the optical fiber 1 is removed as shown in FIG. 11. Then, a coating removal portion is formed in which the bare optical fiber 1a is exposed. As the optical fiber 1, an optical fiber used in normal optical communication such as a quartz-based singulomote fiber is used, and an optical fiber made by adding one or more layers of limbs N to a bare optical fiber or a bare optical fiber is used. Optical fiber cores are preferably used.

Next, the two optical fibers 1 with the coating removed are placed in parallel as shown in Fig. 12, twisted several times as shown in Fig. 13, and the twisted parts are exposed to an oxyhydrogen flame or the like. An optical fiber coupler is created by heating and fusing with a high-temperature heating source and stretching as necessary to form a fused and drawn portion.

In another method, after arranging two optical fibers l in parallel, - as shown in FIG.
Attach each bare optical fiber 1 to both ends of a using thread or adhesive.
After that, as shown in FIG. 15, a high-temperature heating source 4 is used to heat between each of the fixed parts 3 to fuse each optical fiber 1. And if necessary, it is stretched in the direction of the arrow in the figure. Through these fusion and stretching operations, a fused and stretched portion 5 is formed, and an optical fiber coupler 6 is created. Further, in the optical fiber coupler 6 thus obtained, it is preferable that the removed portion of each optical fiber l be reinforced with a case 7 to protect the fused and stretched portion 5, as shown in FIG.

"Problems to be Solved by the Invention" However, the conventional method for manufacturing an optical fiber coupler has the following problems.

In the method of twisting parallel optical fibers and then fusion-stretching, the manufacturing process becomes complicated due to the twisting process, and it is also necessary to twist multiple fibers evenly in the fiber axis direction. Therefore, a precise twisting device is required.

Further, by twisting a plurality of optical fibers, twisting stress is applied to the optical fibers, which may deteriorate the optical coupling characteristics of the optical fiber coupler, leading to an increase in excess loss and deterioration of polarization characteristics.

On the other hand, the method of fixing both ends of the exposed bare optical fiber with thread or adhesive requires detailed features and precision equipment when forming the fixed part, which reduces work efficiency and reduces the fiber optic coupler. There was a problem that led to high prices.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a manufacturing method that can easily manufacture a low-loss, high-performance optical fiber coupler.

[Means for Solving the Problems] As a means for achieving the above object, the present invention provides a method for manufacturing an optical fiber coupler in which a part of two or more optical fibers is fused and stretched to form a fused and stretched portion. The plurality of optical fibers to be fused are held in contact by a grooved holder for holding the plurality of optical fibers, and then the plurality of optical fibers are heated and fused, This is a method for producing a 4-filter fiber capacitor characterized by further stretching.

"Function" Multiple optical fibers to be fused are held in the groove of the holder, and the holder heats and fuses the multiple optical fibers that are in contact with each other. There is no need to fix the fiber with thread or adhesive, simplifying the manufacturing process.

In addition, there is no need to twist the optical fibers together, making it unnecessary to use a precise device for twisting, and the resulting optical fiber coupler also has good optical properties.

"Example" FIGS. 1 to 3 are for explaining an example of the method of the present invention.

In the method for manufacturing an optical fiber bacable according to this example, first,
Two optical fibers 11 with coat-removed portions are arranged in tandem, and both ends of the bare optical fibers 11a of the coat-removed portions are held by holders 12, as shown in FIGS. 1 and 2.

As the optical fiber 11, an optical fiber cable wire such as a quartz-based single moat fiber, which is a bare optical fiber for ordinary optical communication and is coated with a coating, is preferably used.

Further, as shown in FIG. 3, the holder 12 stores two vertically arranged bare optical fibers 11a in the groove 13,
By closing ti14, each bare optical fiber 11a
can be held in contact with each other. Note that the material of this holder 12 is not limited to transparent hard materials such as quartz and plastic, but opaque materials such as metal and ceramics can be used. In addition, the dimensions of the groove 13 should be such that each fiber comes into contact when storing the bare optical fiber 11a, and does not shift when the M14 is closed and fixed. desirable.

Next, the two bare optical fibers +1a connected in tandem between the two holders 12 are heated with a high-temperature heating source such as an oxyhydrogen flame to fuse the two fibers, and then the holders 12 are heated. The fused portion is stretched by uniformly pulling apart one or both of the parts 12. By this fusion-stretching operation, a fusion-stretching portion is formed in a part of the two optical fibers 11, and an optical fiber coupler is created.

In the manufacturing method according to this example, two optical fibers 11 to be fused are held in 113 of the holder 12, and each optical fiber II arranged in contact with the holder 12 is heated and fused, Furthermore, since the optical fiber can be stretched, there is no need to fix the optical fiber with thread or adhesive, which simplifies the manufacturing process. Furthermore, it is not necessary to twist the optical fibers together, making it possible to eliminate the need for a precise device for twisting, and to improve the optical properties of the resulting optical fiber coupler.

FIG. 4 is a diagram showing another example of the above-mentioned holder 12.

In the previous example, an optical fiber coupler was created by fusion-drawing a part of two optical fibers 11 to form a fusion-drawn part, but in the manufacturing method according to claim I, the number of optical fibers 11 is two. For example, as shown in FIG.
A 7:7 type optical fiber coupler constituted by seven optical fibers 11 can be obtained by storing the optical fibers 11 in a 7-by-7 optical fiber coupler by placing them in a contact state and then fusion-stretching them.

5 to 7 are diagrams for explaining other examples of the method of the present invention, and in this example, the method of the present invention is applied to a polarized fiber constructed using a stress-applied polarization-maintaining optical fiber. An example of application to a method for manufacturing a wave-holding optical fiber coupler is shown below.

In this example, two polarization-maintaining optical fibers 19 with coated removed portions are arranged in tandem, and as shown in FIG. Each is held by a holding body 20.

This polarization-maintaining optical fiber 19 consists of a core 1G, stress applying parts 21 arranged on both sides of the core 1G, and a cladding 1 surrounding them.
5, this optical fiber bare wire 19
A coated optical fiber is preferably used.

Further, the transparent holding body 20 is similar to the holding body 12 according to the previous example.
Similarly, a groove 22 for storing two parallel bare optical fibers +9a! 23 is set to H, the two bare optical fibers 19a are inserted into the groove 22, and the straight 23 is closed, so that the bare optical fibers 19a can be held in contact with each other. Note that the material of the transparent holder 20 is not limited to quartz glass, and may be a transparent hard material that can transmit visible light, such as transparent plastic.

Next, the polarization axes of each polarization-maintaining optical fiber 19 held by the transparent holder 20 are aligned. 7 to 9 are diagrams showing an example of the polarization axis alignment operation. In order to align the polarization axis of each polarization maintaining fiber 19, the transparent holder 20
A light source 24 is disposed below the transparent holder 20, and observation is performed using a microscope 25 from above the transparent holder 20. From the position of the core 16 and stress applying portion 21 of each bare optical fiber 19a observed through the transparent holder Check the misalignment of each polarization-maintaining optical fiber 19, and if, for example, the polarization axes C are misaligned by 1llI45 as shown in FIG. The polarization axis C is adjusted to be parallel as shown in FIG. 9 by rotating it as shown by the arrow in the figure. When observing the polarization-maintaining optical fiber 19 without transmitting light as shown in FIG.
eO! High refractive index core 16 made of doped S10°
appears shiny, and the stress applying portion 22, which has a low refractive index and is made of B and 03-doped Sin, appears black, and the direction of the polarization axis can be easily confirmed by microscopic observation.

Next, the two bare optical fibers 19a arranged in tandem in contact between the two transparent holders 20 are heated with a high-temperature heating source such as an oxyhydrogen flame to fuse the two bare fibers 19a. Then, by uniformly separating one or both of the transparent holders 20, the fused portion is stretched.

By this fusion-stretching operation, a fusion-stretched portion is formed in a portion of the two polarization-maintaining optical fibers 19, and a polarization-maintaining optical fiber coupler is created.

In the manufacturing method according to this example, by using the transparent holder 20, the polarization maintaining optical fiber I9 is used as the optical fiber.
When using the transparent holder 20, the polarization axis of the polarization-maintaining optical fiber 19 can be observed to accurately perform one-wave axis alignment. Therefore, it is possible to easily manufacture a polarization-maintaining optical fiber coupler with excellent optical properties, especially polarization properties.

(Manufacturing example 1) Core diameter 8 μm 1 Clad outer diameter 126 μm 1 Covering diameter 40
Using a silica-based single-mode fiber with a cutoff wavelength of 1.18 μm and a cutoff wavelength of 1.18 μm, first, a coat-removed portion of about 5 (lss) is formed in the center of the optical fiber, and two of these optical fibers are arranged in tandem. Both ends were held by a holder shown in Fig. 10. This holder had a width of 3.0 tam and a WII width of 126 μa+.
, i# depth is 240μ-, and the material is transparent glass.
child.

Next, the bare optical fibers between the holders were heated and fused using an oxyhydrogen burner, and further stretched to obtain an optical fiber coupler.

The obtained optical fiber coupler had an excess loss of 0.07 dB at the working wavelength of 1.3 μm.

It showed excellent performance with a branching ratio of 49.7% and polarization dependence of 0.15%.

(Manufacturing Example 2) A polarization-maintaining optical fiber coupler was produced using a stress-applied polarization-maintaining optical fiber. The fiber used has a core diameter of 8 μm.
, cladding outer diameter 125μm, coating diameter 400μm, cutoff wavelength 12μm1 Crosstalk -38dB/lOa
A + stress-applied polarization-maintaining optical fiber was used. 50s+
Two fibers with s-long coat removed parts are arranged in tandem, and both ends of the coat removed parts are held by holders shown in Figure 1θ, and the polarization axes of each fiber are shown in Figure 9. After that, each holder was heated and fused using a burner, and further stretched to obtain a polarization-maintaining optical fiber coupler. The obtained coupler has an excess loss of 0.3 dB, a branching ratio of 50.5%, and a crosstalk at a wavelength of 1.3 μm.
It showed excellent performance of 27 dB.

"Effects of the Invention" In the method for manufacturing an optical fiber coupler according to the present invention, two or more optical fibers to be fused are held in a groove of a holder, and each optical fiber arranged in contact with the holder is heated. Since the first fiber is fused and then stretched, the first fiber is not fixed with thread or adhesive, and the manufacturing process is simplified.

Furthermore, there is no need to twist the optical fibers together, making it possible to eliminate the need for a precise device for twisting, and to improve the optical properties of the resulting optical fiber coupler.

In addition, when using a polarization-maintaining optical fiber as the optical fiber, a transparent holder is used as the holder, and the polarization axis of the polarization-maintaining optical fiber is observed through the transparent holder to accurately align the polarization axis. be able to. Therefore, it is possible to easily manufacture a high-performance polarity-maintaining fiber coupler with excellent optical properties, especially polarization properties.

[Brief explanation of the drawing]

1 to 3 are diagrams for explaining an example of the method of the present invention, in which FIG. 1 is a plan view showing a state in which the tip fiber is held by a holder, FIG. 2 is a side view of the same, Figure 3 is the second
4 is a sectional view showing other examples of the holder shown in FIG. 3, and FIGS. 5 to 7 are for explaining other examples of the method of the present invention. FIG. 5 is a side view showing the state in which the polarization maintaining optical fiber is held by a holder, FIG. 6 is a sectional view taken along the line b-b of FIG. 5, and FIG. 7 is a view showing the polarization maintaining optical fiber. Side view for explaining the axis alignment operation, No. 8
9 and 9 show an example of adjusting the polarization axis, FIG. 10 is a perspective view of the holder used in the manufacturing example, and FIGS. 11 to 16 show the manufacturing process of a conventional optical fiber coupler in order of process. FIG. 11... Optical fiber, 12.18... Holder, 13
．． 17... Groove, 19... Polarization maintaining optical fiber 20.
...Transparent holding body, 22...groove.

Claims (1)

[Claims] A method for manufacturing an optical fiber coupler in which a part of two or more optical fibers is fused and stretched to form a fused and stretched part, the method comprising:
The plurality of optical fibers to be fused are held in contact by a holder having a groove for holding the plurality of optical fibers,
A method for manufacturing an optical fiber coupler, comprising: then heating and fusing the plurality of optical fibers, and further stretching the optical fibers.