JPH02266308A - Manufacture of optical coupler - Google Patents

Abstract

PURPOSE:To attain mass-production of optical couplers by using one optical glass fiber which is varied in its external diameter partially and periodically in the optical fiber lengthwise direction as at least one of optical glass fibers. CONSTITUTION:The optical glass fiber which is varied in its external diameter partially and periodically in the optical fiber lengthwise direction is used as at least one of optical glass fibers. For example, the small-external-diameter part (T1) and large-external-diameter part (T2) of, for example, an optical glass fiber 1 vary periodically and T1 < T2. Namely, the optical glass fiber 1 which is varied in external diameter partially and an optical glass fiber which has a normal external diameter are combined to obtain the optical coupler whose branch ratio is made constant to wavelength. Consequently, the manufacture time of the optical coupler is shortened extremely.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing an optical coupler used to branch and couple light propagating through an optical fiber.

(Prior Art) As an example of a conventional method for manufacturing an optical coupler, there is a "method for manufacturing a single mode evanescent wave optical coupler" disclosed in, for example, Japanese Unexamined Patent Publication No. 83-108311.

In this manufacturing method, two single mode optical fibers, a first and a second, are prepared, the first optical fiber is heated and stretched to reduce its outer diameter, and the first optical fiber and the second optical fiber are This is a method of manufacturing an optical coupler by holding optical fibers in a parallel state, heating and fusing them, and stretching them.

(Problem to be solved) In the conventional manufacturing method described above, it is necessary to prepare two optical fibers and reduce the diameter of one of them by heating and stretching it in advance, which takes manufacturing time during mass production. There is a problem.

Furthermore, if optical fibers are heated and stretched in advance, they will become tapered, but if the outer diameters of the fibers are not uniform, it will be extremely difficult to arrange them in parallel, heat fuse them, and stretch them, and as a result, the fusion will tend to be uneven. There is a problem in that excessive loss in the optical coupler is likely to occur.

(Means for Solving the Problems) The present invention solves the above-mentioned problems and provides a method for manufacturing an optical coupler that enables mass production of optical couplers. The purpose is to use a book whose outer diameter is partially and periodically changed in the longitudinal direction of the optical fiber.

FIG. 1 is a longitudinal sectional view of at least one optical fiber used in the method of manufacturing an optical coupler of the present invention.

In the drawing, (1) is an optical fiber glass, the outer diameter of which changes periodically between a small outer diameter part (r1) and a large outer diameter part (I2), and has a relationship of T<I2.

Also, the outer diameter of the T2 part d1 = 125±3 mm■, d2/d
t-1 is within the range of 5 to 10%.

FIGS. 2 to 4 are explanatory views of specific examples of the method for manufacturing the optical fiber shown in FIG. 1.

Figure 2 shows the capstan drawing line speed over time (periodically).
In this method, the outer diameter of the optical fiber glass is partially and periodically changed by changing the outer diameter of the optical fiber glass.

Optical fiber glass (1) is produced by melting a preform (10) with a heating device (11), taking it up with a capstan (12) and drawing it to a predetermined outer diameter. ) A coating layer is applied on top using a coating device (eye). In this specific example, in the above, the drawing speed (ma) of the capstan (12) is changed temporally (periodically) as shown in (II) of the same figure. Since the drawing speed (ma) and the outer diameter of the optical fiber glass (1) are proportional to the 1/2 power,
In order to keep the outer diameter difference between dl and d8 in the range of 5 to 10% in Fig. 1, it is possible to do so by changing the drawing speed of the capstan (12) by 1.1 to 1.2 times. Become.

At this time, check the outer diameter of the optical fiber glass (1) using an outer diameter monitor (
I3) while monitoring the capstan rotational speed (V)
This can be easily implemented by controlling the

FIG. 3 shows a method of partially and periodically changing the outer diameter of the optical fiber glass by providing a protrusion on a part of the circumference of the capstan.

That is, a protrusion (
12m). By using such a capstan (12), the capstan (I2
), the drawing speed is v1=2R, x as shown in (11) in the same figure.
・From r (rotation speed) periodically v, = 2 R*π・
r, the former being the large diameter part (Tg) and the latter being the small diameter part (Tl) in FIG. Note that (Is') is a roller that moves up and down as the capstan (12) rotates.

FIG. 4 shows a method of partially and periodically changing the outer diameter of the optical fiber glass by installing a group of guide rollers whose pass line length can be adjusted between the heating device and the capstan.

As shown in the drawing, the heating device (11) and the capstan (
A guide roller group (III) is installed between 12). This guide roller group (1B) is composed of two fixed rollers (le6) on the upper and lower sides, a movable roller (18b) located in the middle and movable left and right, and a capstan (
12) When the rotational speed v0 = 2πR-r (rotation speed) is constant, when the guide roller group (1B) is in the state A, the pass line is short and the tension is determined by the capstan (12), but the guide roller group When (I6) is in the state of B, the speed margin of the movable roller (1[ib) changes as shown in (0) in the same figure, the pass line becomes long and the tension becomes large. Thereby, the outer diameter of the optical fiber glass (1) changes periodically.

(Example) An optical fiber was prototyped and tested using the method shown in FIGS. 2 and 3 described above. The structure of the prototype optical fibre-noy was constructed by drawing a preform of a 1,3I band single mode optical fiber, which is normally used for optical communications. (Leg FD 1.5 m, cutoff wavelength 1.21 ■) In the method shown in Figure 2, 8
An experiment was conducted by changing the linear speed of the capstan so that the outer diameter of the optical fiber glass varied by 8% by 1 m at intervals of m.

Specifically, the linear speed of the capstan was set to 40■/
The feeding speed of the preform into the heating device (2.3 m/min) and the furnace temperature (2010° C.) were set so that the outer diameter of the optical fiber was 1251 min. Linear speed 47, which would give an 8% difference in outer diameter from cabtan speed 40-7 minutes
The change in outer diameter was measured using an outer diameter monitor. At a linear speed of 4711 minutes, the outer diameter was 113 to 1!7 μm, and a difference in outer diameter of about 8% could be obtained.

The results are shown in FIG. 5(a). In this method, the section where the outer diameter of the optical fiber glass becomes smaller is made longer.
Unless the length is 1 m or more, it is difficult to obtain a small and uniform optical fiber outer diameter.

The method shown in FIG. 3 was also tested using a preform similar to that shown in FIG. The shape of the capstan used is as follows.

2 Rs” 1000*m Ts=
2700-day 2 R2= 1lB8■■
T*=400 error-r=15rpi+ The results are as shown in FIG. 5(0).

In the method shown in FIG. 2, overshoot was observed when the outer diameter of the optical fiber glass was increased, but there is no problem in practical use. In the method shown in FIG. 3, it was possible to shorten the small outer diameter portion of the optical fiber, and it was also possible to stably produce a prototype.

The difference in outer diameter of optical fiber glass (the ratio of the outer diameter difference between the maximum diameter and the minimum diameter) is set to 8% by changing the fusion conditions during the manufacture of the optical coupler when it is in the range of 5 to 1G%. 90-50%
It is possible to create an optical coupler with a branching ratio of 0. Usually, a branching ratio of 110 to 50% is often required (,
With the above outer diameter difference, a branching ratio of 90 to 50% is achieved at a wavelength of 1.2 to
It is possible to keep it approximately constant between wavelengths of about L and S-■.

Furthermore, if markings are made using an inkjet printer or the like on the coating layer at the portion where the outer diameter changes, work efficiency during the production of the optical coupler will be improved.

(Effects of the Invention) As explained above, according to the method for manufacturing an optical coupler of the present invention, an optical fiber glass whose outer diameter is partially changed in the optical fiber manufacturing process and an optical fiber having a normal 125 g outer diameter are used. By combining fiber glasses, it is possible to obtain an optical coupler that keeps the branching ratio constant with respect to wavelength, compared to the conventional method of stretching optical fiber glass each time the optical coupler is manufactured.
The manufacturing time of optical couplers is significantly shortened, which is extremely effective for mass production of optical couplers.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of at least one optical fiber used in the method of manufacturing an optical coupler of the present invention. Figures 2 to 4 are explanatory diagrams of specific examples of the method for manufacturing the optical fiber shown in Figure 1. Figure (A) is a configuration diagram of the main part, and Figure (B) is a diagram of the capstan or movable roller. It is a relationship diagram between rotation speed and time (optical fiber length). 5(a) and 5(b) are both diagrams showing the relationship between the outer diameter of the optical fiber and the length of the optical fiber in the embodiment of the present invention. 1... Optical fiber glass, 2... Coating layer, 1G...
- Preform, 11... Heating device, 12... Capstan, 13... Outer diameter monitor, 14... Coating device, 15... Presser roller, 1... Guide roller group, 16a. ...Fixed guide roller, +6b...Movable guide roller. Multi-map (a) Wharf map

Claims (7)

[Claims] (1) A method for manufacturing an optical coupler in which a plurality of optical fiber glasses exposed by removing a part of the coating of the optical fiber are arranged in parallel, heat-fused, and stretched, wherein at least one of the optical fiber glasses is 1. A method of manufacturing an optical coupler, comprising using a book whose outer diameter is partially and periodically changed in the longitudinal direction of an optical fiber. (2) The method for manufacturing an optical coupler according to claim (1), characterized in that when drawing the optical fiber glass, tension is applied so that the optical fiber glass is partially and periodically stretched and reduced in diameter to change its outer diameter. . (3) The method for manufacturing an optical coupler according to claim (2), wherein the outer diameter of the optical fiber glass is partially and periodically changed by controlling the rotational speed of the capstan. (4) Manufacture of the optical coupler according to claim (2), characterized in that the outer diameter of the optical fiber glass is partially and periodically changed by using a capstan having a protrusion on a part of the circumference. Method. (5) A group of guide rollers that can adjust the length of the pass line is installed between the drawing furnace and the capstan, and the tension of the optical fiber glass is changed to partially and periodically change the outer diameter of the optical fiber glass. A method for manufacturing an optical coupler according to claim (2). (6) Claim (1) characterized in that the amount of variation in the outer diameter of the optical fiber glass is within a maximum range of 5 to 10%.
) to (5), the method for producing an optical fiber coupler. (7) The method for manufacturing an optical coupler according to any one of claims (1) to (5), characterized in that, in the periodic change in the outer diameter of the optical fiber glass, the maximum outer diameter of the optical fiber glass is 125±3 μm.