JPH03138607A - Production of fiber type coupler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a method for 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]

In this fusion drawing method, as shown in FIG. 5, part of the coating of two optical fibers is removed to form an exposed part (501).
After that, the exposed portions are twisted to make them come into close contact with each other, or are tightly fixed in parallel, and the bundled portions are stretched while being heated and fused with a burner or the like (502). At this 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 bonded and fixed 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 (see Figure 6). Therefore, if a constant branching ratio is required over a wide wavelength band, the top part of the branching ratio curve in Figure 6 should match the wavelength band used, and the branching ratio at this part (R
Ideally, it should be manufactured so that max) is the required branching ratio.

However, in the conventional method, the branching ratio is controlled by the length of stretching the two optical fibers μ, that is, the distance between the cores when they are stretched, to obtain predetermined coupler characteristics. However, in order to obtain a predetermined branching ratio at a predetermined wavelength, it is necessary to select an inclined portion that is far from the branching ratio at the top (Rmax in FIG. 6).

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

However, as shown in Figure 7, we found that there is a difference between the number of traverses (heating time) in which the burner is reciprocated in the optical axis direction of the optical fiber with respect to the heated area (exposed part) of the optical fiber, and the maximum branching ratio. It was discovered that there is a certain relationship between One of the findings is that when dividing the heating time into region A, where the heating time is short, and region B, where the heating time is long, with a heating time of approximately 120 times in terms of the number of traverses, the maximum branching ratio is traversal in region A. It decreases linearly as the number of traverses increases, and remains constant (stable state) in region B even if the number of traverses increases. Another problem is that the maximum branching ratio changes depending on the outer diameter difference between the two optical fibers, and especially in region B, the maximum branching ratio is determined only by the outer diameter difference (stable state!! 3). be.

The present invention focuses on the above two points, and an object of the present invention is to provide a method for manufacturing a fiber-type coupler that can obtain a coupler having an arbitrary constant branching ratio over a wide wavelength band with good reproducibility.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a method for manufacturing a fiber-type coupler, in which a plurality of optical fibers are stretched while being heated and fused at the exposed portion where the coating is removed, to form a coupler. It is characterized by using optical fibers with different outer diameters, and heating the exposed portions before stretching until the branching ratio becomes stable.

In this case, during the heating, it is preferable to use a heat source that partially heats the exposed portion, and to convert the preset time into the number of reciprocating movements of either the heat source or the exposed portion in the optical axis direction.

[Effect]

According to claim 1, by using optical fibers whose exposed portions have different outer diameters and heating the exposed portions before stretching until the branching ratio becomes stable, the maximum branching can be achieved due to the difference in the outer diameters of the optical fibers. Once the ratio is determined, a predetermined maximum branching ratio can be easily obtained without requiring delicate control of heating time.

Furthermore, if the heat source and the exposed portion are relatively reciprocated in the optical axis direction as in claim 2, even if the heat source can only partially heat the exposed portion, it becomes possible to heat the entire exposed portion, and
The heating time until the branching ratio reaches a stable state can be easily controlled by the number of reciprocating movements.

〔Example〕

First, an apparatus for manufacturing a fiber coupler embodying the present invention will be explained 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 through the clampers 3.3, and a part of the covering is removed from the clampers 3.3 to expose an exposed part F a 1 s F a
Optical fibers Fl (large diameter) and F2 (small diameter) having different outer diameters (cladding diameters) are fixed. Exposed part F
a l and F a 2 are fixed so as to be located between both clampers 3.3, and a burner 4, which is a heat source, is arranged directly below them. And both exposed parts FatSFa2
is heated by burner 4, and then both fine movement stages 2.
2 is stretched by minute movement in the opposite direction, and coupler C is formed. Further, the burner 4 is configured to be able to reciprocate between the heating regions of the exposed portions F a 1 and F a 2 in the optical axis direction by a reciprocating device 5, and the heating time is determined by the number of reciprocating movements, that is, the number of traverses. be done.

The exposed portions Fat, Fa2 of the two optical fibers Fl, F2 with different outer diameters are formed in advance by optical fibers F, F with different outer diameters.
or by processing the exposed portion Fa of either one of the optical fibers F1F of the same diameter to a smaller diameter by etching, stretching, or the like.

The manufacturing process of coupler C using the above-mentioned apparatus will be explained in detail with reference to FIG.

In step 301, optical fins Fl having different outer diameters,
Part of the covering of F2 is removed to form exposed parts Fat and Fa2, and these exposed parts Fat and Fa2 are brought into close contact and attached to the clamper 3.3. In this case, the exposed portion F a 1 ,
F a 2 may be twisted together.

In steps 302 and 303, the burner 4 is reciprocated by the reciprocating device 5 while the exposed portion FalSF is brought into close contact with the burner 4.
Heat and fuse a2. At that time, the heating time is determined by the number of traverses of the burner 4 based on a constant moving speed, and is heated until the branching ratio reaches a stable state, that is, the number of traverses shown in Fig. 7 is about 120 times or more. Heating is performed up to area B.

In steps 304 and 305, the clamper 3.3 is slightly moved in directions opposite to each other in the optical axis direction to remove the exposed portion Fat.
, Fa2 is stretched. 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 portion Fat s Fa2 is stopped to form the coupler C.

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

If heating is performed to the B region shown in FIG. 7 before stretching in this way, the maximum branching ratio is determined by the difference in the outer diameter of both optical fibers Fl and F2, and this is used as the necessary branching ratio at a predetermined wavelength during stretching. By doing so, it is possible to stably obtain a coupler C having characteristics such that the required branching ratio is the maximum branching ratio.

Next, based on FIG. 4, experimental results of the fiber coupler according to the above embodiment will be explained. In this experiment, two optical fibers Fl and F2 with outer diameters of 125.0 μm and 111.3 μm, respectively, were used, and their coatings were removed over a length of 25 mm to form exposed portions Fat and Fa2. Then, clampers 3.3 are fixed on both sides of the exposed parts Fal and Fa2 so that they are in close contact with each other, and this is heated with a burner 4 having a diameter of Q and 5 mm and using 15 cc/min of propane and 30 cc/min of oxygen as combustion gas. I did it like that.

For heat fusion using burner 4, the traverse length is 8 mm.)
Rubber speed is 3mm/s, number of rubbers is 12
0 times, and 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, in contrast to curve A showing the characteristics of the conventional coupler under the above-mentioned equivalent conditions, curve B shows the characteristics of coupler C of this example, and the wavelength 1 .5
It can be seen that the branching ratio is stable over several hundred nm around 5 μm.

Furthermore, when the branching ratio was measured using 10 couplers C produced under the same conditions as in the above experiment, the branching ratio of each coupler C was within ±2% of the desired branching ratio, It was confirmed that a coupler C having good reproducibility and a constant branching ratio over a wide wavelength band could be obtained.

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 burner 4 is reciprocated, but the fine movement stage 2.2 may be reciprocated.

〔Effect of the invention〕

As described above, according to the present invention, the maximum branching ratio can be easily obtained without requiring strict control of the heating time, and the necessary branching ratio selected at the time of stretching matches the maximum branching ratio. This has the effect that a coupler having a constant branching ratio characteristic over a wide wavelength band around the used wavelength can be manufactured with good reproducibility.

[Brief explanation of the drawing]

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, the difference in outer diameter of the optical fiber, and the maximum branching ratio. 4... Burner, 5... Reciprocating device, F 1. F2
...Optical fiber, Fal, Fa2...Exposed part, C.
...Coupler. Figure 21 Flow of manufacturing method Figure 3 Uno Roku Senju Figure Figure Prior art Figure Bar 1 Trabase TgJ ((times) 2\-Atrano ) The number of times and the outer circle of the heavenly fiber is here.

Claims (1)

[Claims] 1. A method for manufacturing a fiber-type coupler, in which a plurality of optical fibers are stretched while being heated and fused at the exposed portions of the optical fibers where the coating is removed, to form a coupler, each exposed portion 1. A method of manufacturing a fiber coupler, which uses optical fibers having different outer diameters and which comprises heating the exposed portion of the fiber before stretching until the branching ratio becomes stable. 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.