JPH03255411A - Production of optical fiber coupler - Google Patents

Abstract

PURPOSE:To smoothly perform the drawing process by specifying the coating characteristic or the like of a multiple optical fiber. CONSTITUTION:A part of the coating of a multiple optical fiber 1 is removed to disclose a glass part 2a of the coated optical fiber, and the glass part 2a is fused and drawn. The multiple optical fiber 1 is used which has such structure that the force due to buckling for drawing is <20% of drawing tension. Thus, drawing is smoothly performed to produce optical fiber couplers of good reproducibility when the multiple optical fiber 1 is used to mass-produce optical fiber couplers.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing an optical fiber coupler, and particularly to a method of manufacturing an optical fiber coupler using a multicore optical fiber.

(Prior Art) Conventionally, in constructing an optical communication system, an optical data link network, etc., an optical branching device that distributes optical signals emitted from a light source at a desired ratio is an important component. One type of optical splitter is an optical fiber coupler, which usually removes a portion of the longitudinal coating of multiple optical fibers to expose the glass portion, and then twists or parallelizes the fibers. The most suitable method for manufacturing optical fiber couplers is the so-called fusion-stretching method, in which the fibers are fused together, heated and melted using a heat source such as an acetylene burner, and then stretched under constant tension. It is said that.

In this case, it is necessary to handle a plurality of optical fibers separately, which is not efficient. In view of this, our company is developing a manufacturing method that uses multi-core optical fibers to automate the manufacturing process and shorten working time.

A manufacturing method using a multicore optical fiber will be explained with reference to FIGS. 1 and 2.

FIG. 1 is an example of a manufacturing apparatus, and FIG. 2 is an explanatory diagram of the manufacturing process. In the figure, 1 is a double-core optical fiber, 2a,
2b is the glass part with the coating removed, 2 is the turnip body part, 3
4 is a stretching stage, 4 is a clamper, 5 is an optical fiber grip part, 6 is a heating source such as an acetylene burner, 7 is a fixing member, 8
is a protective member.

First, the twin-core optical fiber 1 is gripped by the gripper 5, and a part of its coating is removed to expose the glass portions 2a and 2b of the core, and then the clamper 4 supported by the stretching stage 3 is used to cover the fiber. (Fig. 2 (A)). Next, glass part 2
The glass portions 2a and 2b are fixed in a state in which they are in contact with each other by the fixing member 7 (FIG. 2(B)), and the glass portions 2a and 2b are heated and melted by the heat source 6 to be fused. After fusion, the fixing member 7 is removed, a constant tension is applied to the stretching stage while monitoring the branching ratio, and the fused portion is heated and stretched to form the turnip main body 2 (Fig. 2(C)). When the branching ratio is obtained, the heating and stretching are stopped, and the optical fiber coupler is manufactured by molding with the protective member 8 (FIG. 2(D)).

In such an optical fiber coupler manufacturing method, since it is necessary to grip the optical fiber with an optical fiber gripping part, the optical fiber is fixed at that part, and during stretching, the twin-core optical fiber 1 is drawn as shown by the dotted line in FIG. This causes bending.

This bending exerts a force against the stretching tension at the time of stretching, making it impossible to stretch smoothly and causing a decrease in the production yield of optical fiber couplers. It had become.

(Problems to be Solved by the Invention) In order to solve the above-mentioned problems, the present invention improves the multi-core optical fiber, particularly its coating characteristics, so that the drawing process can be carried out smoothly. The object of the present invention is to provide a method for manufacturing an optical fiber coupler.

(Means for Solving the Problems) The present invention involves removing a part of the coating in the longitudinal direction of a multi-core optical fiber to expose a glass portion of the optical fiber, and fusing and stretching the glass portion. This method of manufacturing an optical fiber coupler is characterized by using a multi-core optical fiber having a structure in which the force due to buckling of the multi-core optical fiber during stretching is 20% or less of the stretching tension.

Each fiber in a multicore optical fiber has a coated outer diameter of 140 to 200 μm (the outer diameter of the glass part is 125 μm).
m) can be used.

(for production) This will be explained using the twin-core optical fiber shown in FIG. 3 as an example.

In the figure, 21 is the glass part of the core wire, 22 is the primary coating of the core wire,
Reference numeral 23 denotes a secondary coating of the core wire, and 24 an outer sheath that combines two of the core wires 21 to 23 to form a twin-core optical fiber.

As shown in Figure 1, when holding both ends of this twin-core optical fiber and stretching the central part, when the optical fiber is stretched, a bend naturally occurs between the stretching stage and the gripped part. . This is a phenomenon called buckling, and the force P that opposes this bending is expressed by the following formula (published by Shokabo, Kinsen, edited by Mechanics of Optical Materials, "Mechanics of Materials" Revised Edition, No. 149)
page).

However, L: distance between the optical fiber gripping part and the stretching stage 11 [m
m] E: Young's modulus [kg/mm'' = cross-sectional moment. In this case, the moment E and Young's modulus E of the composite are expressed by the following formula.

However, SL is the cross-sectional area of the i-th layer structural material of the twin-core optical fiber, EL is the Young's modulus of the i-th layer structural material of the twin-core optical fiber, and ■ is the cross section of the twin-core optical fiber. It is a moment.

Therefore, the cross-sectional area of the structural material of the twin-core optical fiber is Si
, Young's modulus E4, and moment of area E, the force P due to buckling can be suppressed to an appropriate value.

When the properties of the prototype optical fiber coupler were measured, it was found that when the force P due to buckling was less than 20% of the stretching tension, stretching could be carried out smoothly, and an optical fiber coupler with the desired characteristics could be manufactured. .

(Example) An example of a twin-core optical fiber having the structure shown in FIG. 3 will be described. The first layer is a quartz fiber with an outer diameter of 125 a
m + Young's modulus 7000 kg/mm2 The second layer is the primary coating, outer diameter 200 μm, Young's modulus 10 kg/mm2, the third layer is the secondary coating, outer diameter 250 um, Young's modulus 100
kg/mm2, the fourth layer is the outer coating, which has a Young's modulus of 100kg/mm2, and the outer diameter is 0.5mm.
Considering it as a circular cross section, and assuming that 1 is 400mm, E=944 [kg/mm2 I=5.2x
lO-3 [mm'], EI = 4.90 [kg/mm'' P = 0.6
2 [become g-co.

Since the stretching tension was 3 g, the buckling force P could be reduced to 20% or less compared to the stretching tension.

For comparison, when only the two core wires described above were used without using a two-core type, P=0.017 g.

From this, the second moment of area ■
It can be seen that is dominant. For these reasons,
In order to reduce the force opposing the drawing tension, it is effective to reduce the outer diameter of each core of the twin-core optical fiber.

At our company, the optical fiber has a cladding diameter of 125μm,
When using a normal 1.3 μm band single mode fiber with an MFD of 9.5 μm and a cutoff wavelength of 1°2 μm, a coated fiber with an outer diameter of 250 μm was used;
The outer diameter of the coating was reduced by using a layer-only coating with a Young's modulus of 30 kg/mm 2 .

The outer diameter of the coating is 140 μm, 180 μm, 200 μm,
We prototyped four types of optical fiber cores with a diameter of 230 μm, and coated these two cores with a material with a Young's modulus of 30 kg/mm, which is the same as the Young's modulus of the coating of the core wires, to create a twin-core optical fiber. The outer diameter of each twin-core optical fiber was 31
They were 0 μm, 400 μm, 420 μm, and 480 μm. Using these, we fabricated a prototype optical fiber coupler.

As for the stretching method, a stretching tension of 3 g was applied, a 5 mm heating area was stretched at a constant speed of approximately 13 mm/min using an oxyhydrogen burner, and the branching ratio was monitored to be 50% at 1.3 μm. I created Kabra.

In the stretching process, stretching could be performed smoothly. Also, the EI at this time is 1°74.2.96, respectively.
, 3.27, 4.31.

From these results, it was found that smooth stretching can be achieved when the force due to buckling of the multicore optical fiber during stretching is 20% or less of the stretching tension.

In addition, when using a normal 1.3 μm band single mode fiber with a cladding diameter of 125 μm, it was confirmed that the appropriate coating outer diameter of each fiber constituting the multicore optical fiber is 140 to 200 μm. .

(Effects of the Invention) As is clear from the above description, according to the present invention, when mass-producing optical fiber couplers using multi-core optical fibers, drawing is possible by using suitable twin-core optical fibers. This process can be carried out smoothly and has the effect of producing an optical fiber coupler with good reproducibility.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams of the manufacturing process of an optical fiber coupler, and FIG. 3 is a sectional view of an example of a twin-core optical fiber. DESCRIPTION OF SYMBOLS 1... Twin-core optical fiber, 2a, 2b... Glass portion from which coating has been removed, 2... Cobra main body, 3... Stretching stage, 4... Clamper, 5... Optical fiber Gripping portion, 6... heating source, 7... fixing member, 8... protection member.

Claims (1)

[Claims] A method for manufacturing an optical fiber coupler in which a part of the longitudinal coating of a multi-core optical fiber is removed to expose a glass part of the optical fiber core, and the glass part is fused and drawn. 1. A method for manufacturing an optical fiber coupler, characterized in that a multicore optical fiber having a structure in which the buckling force of the cored optical fiber is 20% or less of the stretching tension is used.