JPH0351808A - Manufacture of fiber type coupler - Google Patents

Abstract

PURPOSE:To obtain the coupler which has an optional constant branch ratio in a wide wavelength band by heating exposed parts before drawing for a preset time. CONSTITUTION:A couple of clamper 3 is set opposite each other across fine adjusting stages 2 provided on a machine base 1 and an optical fiber F whose jacket is removed partially to have the exposed parts Fa is fixed in the clampers 3. The exposed part Fa is positioned between both the clampers 3 and a burner 4 as a heat source is arranged right below the exposed parts. Both the exposed parts Fa are heated by the burner 4 for the preset time and then drawn by the reverse-directional movement of both the fine adjusting stages 2. Consequently, the coupler C which has the constant branch ratio characteristics over a wide wavelength range nearby in-use wavelength can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention involves forming a coupler by stretching a plurality of optical fibers while heating and fusing them at the exposed portions of the optical fibers where the coating is removed. This invention relates to a method of manufacturing a fiber coupler using a so-called fusion drawing method.

[Conventional technology]

A fiber coupler is a device that splits and couples light between multiple optical fibers, and melt-drawing is currently considered the most suitable method for manufacturing single-mode fiber couplers (“Recent optical fiber "Coupler Technology", Obtronics (1988) No. 5, p. 125), :0
) As shown in Fig. 5, the fusion drawing method involves removing part of the coating of two optical fibers to form an exposed part (501), and then twisting the exposed parts to bring them into close contact with each other. Alternatively, the bundled portions are tightly fixed in parallel and stretched while being heated and fused using a burner or the like (502). that time,
The light entering from one end of the optical fiber is measured at the other end to detect the optical branching ratio (step 503), and the stretching is stopped when a predetermined branching ratio is obtained (step 504). Finally, it is fixed and adhered to a protective member to produce a fiber coupler (step 505).

[Problem to be solved by the invention]

By the way, couplers made by the fusion-stretching method use evanescent waves that propagate within the optical fiber to branch light, but since the strength of the evanescent waves strongly depends on the wavelength of the light, the splitting of the coupler The ratio also depends on the wavelength (6th
(see figure). Therefore, if a constant branching ratio is required over a wide wavelength band, the top part of the branching ratio curve in Fig. 6 should match the wavelength band used, and the branching ratio of this part (Rmax in Fig. 6) should be ) must be manufactured so that it has the required branching ratio.

On the other hand, in the conventional method, the branching ratio is controlled by the length to which the two optical fibers are drawn, that is, the distance between the cores when they are drawn, to obtain predetermined coupler characteristics. According to this, when trying to obtain a predetermined branching ratio at a predetermined wavelength, the branching ratio at the top (R
I had no choice but to choose a sloped section far away from max).

For this reason, it has been extremely difficult to obtain a coupler that has a constant branching ratio over a wide wavelength band around the wavelength used.

However, we discovered that there is a certain relationship between the heating time before stretching and the branching ratio. This discovery is based on the relationship between the maximum branching ratio and the number of traverses (heating time) in which the burner is reciprocated in the optical axis direction of the optical fibers in the heating region of a bundle of multiple optical fibers, as shown in Figure 7. There is a certain relationship between the two, and the maximum branching ratio can be easily obtained by active heating before stretching.

The present invention has focused on this, and an object of the present invention is to provide a method for manufacturing a fiber-type coupler that obtains a coupler having an arbitrary constant branching ratio over a wide wavelength band.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention provides a method for manufacturing a fiber-type coupler in which a coupler is formed by stretching a plurality of optical fibers while heating and fusing them at the exposed portion where the coating of the optical fiber is removed. It is characterized by heating the previously exposed part for a preset time.

In this case, a heat source that partially heats the exposed portion is used for the heating, and a preset time is converted into the number of reciprocating movements of either the heat source or the exposed portion in the optical axis direction. is preferred.

[Effect]

According to the present invention, by actively heating the exposed portion before drawing, unlike the conventional method in which the branching ratio is simply controlled by the proximity distance between cores, multiple optical fibers existing individually are gradually integrated. Any state in the process of increasing can be selected, and the maximum branching ratio can thereby be easily controlled. Then, by selecting the necessary branching ratio for the wavelength used by stretching, it is possible to automatically select the maximum branching ratio for the wavelength used.

Further, as in claim 2, by relatively reciprocating the heat source and the exposed portion in the optical axis direction, even if the heat source can only partially heat the exposed portion, it is possible to heat the entire exposed portion. , the heating time can be controlled by the number of reciprocating movements.

〔Example〕

First, a fiber coupler manufacturing apparatus in which the present invention is implemented will be described based on FIGS. 1 and 2.

In this manufacturing equipment, a fine movement stage 2.2 is installed on the machine base 1.
A pair of clampers 3.3 are opposed to each other via a pair of clampers 3.3, to which optical fibers F, F, whose coatings have been partially removed to form exposed portions Fa, are fixed. The exposed portion FaSFa is fixed so as to be located between both clampers 3.3, and a burner 4, which is a heat source, is arranged directly below it. Then, both exposed portions Fa%Fa are heated by the burner 4, and then stretched by minute movement of both fine movement stages 2.2 in opposite directions, thereby forming the coupler C. The burner 4 is configured to be able to reciprocate in the optical axis direction between the heating regions of both exposed portions Fa by a reciprocating device 5, and the heating time is determined by the number of reciprocating movements, that is, the number of traverses.

This manufacturing process will be explained in detail with reference to FIG.

In step 301, the coatings of the optical fibers F, F are partially removed to form exposed portions Fa, Fa, and the exposed portions Fa, Fa are brought into close contact and attached to the clamper 3.3. In this case, the exposed portions Fa may be twisted together.

In steps 302 and 303, the burner 4 is reciprocated by the reciprocating device 5 while the exposed parts Fa and Fa are brought into close contact with each other.
Heat and fuse. At this time, the heating time is determined by the number of traverses of the burner 4 based on a constant moving speed.

In steps 304 and 305, the clamper 3.3 is slightly moved in directions opposite to each other in the optical axis direction, so that the exposed portion Fa,
Stretch Fa. Further, in step 305, the light branching ratio is monitored by measuring the light incident from one end of the optical fiber F at the other end during the stretching process. Note that heating during stretching is performed at a low temperature that does not allow fusion to proceed.

In step 306, when a predetermined branching ratio is obtained, the stretching and heating of the exposed portions Fa and Fa are stopped to form the coupler C.

In step 307, the coupler C is connected to a protective member (not shown).
Fixed to.

By going through such a process, the maximum branching ratio can be obtained by heating before stretching while traversing the burner 4, and by stretching this to the necessary branching ratio at a predetermined wavelength, the necessary branching ratio can be made the maximum branching ratio. A coupler C having the following characteristics can be obtained.

Next, based on FIG. 4, experimental results of the fiber coupler according to the above embodiment will be explained. In this experiment, the diameter was 0.5
Propane 30cc/min/oxygen 3 using mm burner 4
0 cc/min was used as the combustion gas. After removing the coating of the two optical fibers F and F over a length of 25 mm, this exposed portion Fa is formed.

Using clamper 3.3 on both sides of Fa, both exposed parts FaSF
Fix it by making sure that the parts a are in close contact with each other. The traverse length of the heat fusion using the bar 4 is gmm.

Traverse speed: 3mm/s, number of traverses: 5
It was 5 times. The stretching was stopped at a branching ratio of 80% at a wavelength of 1.55 μm.

According to this experiment, as shown in FIG. 4, curve A shows the characteristics of the conventional coupler under the same conditions as described above, while curve B shows the characteristics of coupler C of this example, and the wavelength 1.
It can be seen that the branching ratio is stable over several hundred nm before and after 55 μm.

In this embodiment, the burner 4 is used as a heat source, but a heat source using electrical resistance may also be used. Furthermore, in the case of a heat source such as the burner 4 that can heat the whole body instead of partial heating, it goes without saying that the heat source may be directly controlled by the heating time without reciprocating the heat source.

Further, in this embodiment, the bar 4 is moved back and forth, but the fine movement stage 2.2 may be moved back and forth.

Further, the two optical fibers FSF may have the same diameter or may have different diameters.

〔Effect of the invention〕

As described above, according to the present invention, since the required branching ratio selected at the time of stretching matches the maximum branching ratio, it is possible to manufacture a coupler having a constant branching ratio characteristic over a wide wavelength band around the wavelength used. have

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an overview of a fiber coupler manufacturing apparatus embodying the present invention, FIG. 2 is an enlarged side view of the exposed portion, and FIG. 3 is a flow diagram showing the manufacturing process of the fiber coupler. Figure 4 is a wavelength characteristic diagram of the coupler obtained from the experimental results of this example, Figure 5 is a flow diagram showing the manufacturing process of a conventional fiber type coupler, Figure 6 is a characteristic diagram of branching ratio and wavelength. FIG. 7 is a diagram showing the relationship between the number of traverses and the maximum branching ratio. 4...Burner, 5...Reciprocating device, F...Optical fiber, Fa...Exposed part, C...Coupler.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a fiber coupler, in which a plurality of optical fibers are stretched while being heated and fused at the exposed portion of the optical fiber where the coating is removed, to form a coupler, comprising: A method for manufacturing a fiber coupler, characterized by heating an exposed portion for a preset period of time. 2. When heating, a heat source that partially heats the exposed portion is used, and a preset time is converted into the number of reciprocating movements of either the heat source or the exposed portion in the optical axis direction. A method for manufacturing a fiber coupler according to claim 1.