JPH03107106A - Juncture of different diameter optical fibers and production thereof - Google Patents

Abstract

PURPOSE:To lessen the light loss of a juncture by diametrally reducing the front end of the core of the large-diameter optical fiber from which the clad is removed and fusion slicing the end face of the small-diameter optical fiber from which the clad at the end is removed to the diametrally reduced end face. CONSTITUTION:The front end of the plastic clad 2A of the large-diameter optical fiber 2 is removed to expose the front end of the glass core 2B. The front end of this core 2B is then pushed stepwise at every prescribed time into a container 9 filled with hydrofluoric acid 8 and is thereby dissolved; thereafter, the front end is washed to obtain the diametrally reduced core 5 which is reduced stepwise in diameter. The plastic clad 3A at the front end of the small-diameter optical fiber 3 is then removed to expose the front end of the glass core 3B. The front end face of this core 3B and the front end of the diametrally reduced core 5 are fusion-spliced concentrically to form the juncture 6. The diametrally reduced core 5, the fusion spliced part 6, and the exposed part of the large-diameter optical fiber 2 and the small-diameter optical fiber 3 are coated with a silicone resin or the like. The different diameter optical fibers are thus connected at the small light loss and with the simple construction in such a manner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a splice of 1112 large plastic nac glass core optical fibers having different core diameters and a method for manufacturing the same.

[Conventional technology]

Such a connection of two thick and thin plastic clad glass core optical fibers is used, for example, in an automatic solar light concentrating transmission device that utilizes natural sunlight as it is as light. Automatic solar light concentration and transmission equipment collects sunlight while facing the sun and automatically changes its angle, and sends it to the required location through an optical fiber cable.It has a wide range of applications, so it can reduce the overall cost. Its spread is being measured. By the way, in this solar automatic concentrating and transmitting device, due to the difference in circumference of the sun, it is necessary to input the light into an optical fiber having a large core diameter (for example, 8OOOLII11 diameter). Also, in order to make the intensity distribution of the emitted light uniform at the light emitting end, it is preferable to use an optical fiber with a thick core diameter.However, the price of the optical fiber is 2 times the core diameter.
Since the transmission distance increases in proportion to the multiplication factor, the transmission distance with a large diameter optical fiber becomes long (which increases the cost of the entire system. Therefore, by connecting two plastic clad glass core optical fibers with a thick diameter It is possible to transmit long distances using diameter optical fibers, reducing overall costs.

Conventionally, a ferrule shown in FIG. 4 has been known as a connection section between two thick and thin plastic clad glass core optical fibers of this type.

That is, the large-diameter optical fiber a and the small-diameter optical fiber b are fixed to ferrules c and d, respectively, and are butt-connected using an adapter e.

[Problem to be solved by the invention]

The butt connection using ferrules c and d described in the conventional technology is expensive because it is necessary to prepare one that matches the diameter of each optical fiber, and it is also difficult to connect from a large diameter optical fiber to a small diameter optical fiber. In the case of light incident on the optical fiber, there was a problem in that the optical loss due to the connection was large. In other words, in the case of light entering from a large diameter optical fiber to a small diameter optical fiber, the loss of butt connection reaches its limit when the light intensity per unit area is the same value, and as shown in Figure 4, the radius of the large diameter optical fiber a is If rl+radius of small diameter optical fiber b is r2,
The optical loss is, therefore, for example r+=400μ−9rz=
If it is 100 μs, the optical loss will be 12 dB or more,
This results in a large loss of light.

The present invention has been made in view of the above-mentioned problems of the conventional technology, and an object of the present invention is to provide a connection section for different types of optical fibers that is inexpensive and has low optical loss, and a method for manufacturing the same. It is something to do.

[Means to solve the problem]

In order to achieve the above object, the connecting portion of different types of optical fibers of the present invention is provided by removing the cladding of the large diameter optical fiber at the connecting portion of two thick and thin plastic clad glass core optical fibers having different core diameters. The tip of the core is gradually reduced in diameter, the end face of the small diameter optical fiber from which the cladding at the end has been removed is fusion spliced to the reduced diameter end face of the large diameter optical fiber, and the cladding removed portion of this joint is made of a material equivalent to the cladding. It has been recoated.

As a manufacturing method, there is a method in which the diameter-reduced core is formed by sequentially pushing the tip of the core after removing the cladding into hydrofluoric acid.

[Effect]

The core of the large-diameter optical fiber is sequentially reduced in diameter and fusion-spliced with the core of the small-diameter optical fiber, and is re-coated with a cladding equivalent material, so even when light enters from the large-diameter optical fiber to the small-diameter optical fiber. Since light passes through a smooth reflection path due to the reduced diameter core, optical loss is reduced. Moreover, it has a simple structure of fusion re-coating, and can be formed at low cost.

In the method for producing a reduced-diameter core by sequentially pressing into hydronic acid, a desired reduced-diameter shape can be obtained reliably and easily by controlling the speed of pressing and the like.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

Fig. 1 is a cross-sectional view showing the connecting portion of optical fibers with different diameters, Fig. 2 is a drawing showing the manufacturing process of the connecting portion of optical fibers with different diameters, and Fig. 3 is a diagram showing the manufacturing process of reduced diameter cores of various shapes. It is a graph diagram.

First, the structure of the connecting portion of the optical fiber with different diameters will be explained, and then the manufacturing method thereof will be explained.

In FIG. 1, a connecting section 1 of different diameter optical fibers includes a large diameter optical fiber 2, a small diameter optical fiber 3, a reduced diameter core 5 between them, a fusion splicing section 6, and a coating section 7 that covers these. It consists of.

The large diameter optical fiber 2 is a plastic clad glass core optical fiber consisting of a plastic clad 2A and a glass core 2B. Further, the small diameter optical fiber 3 is also a similar plastic clad glass core optical fiber. The glass core is usually made of quartz glass, but may also be made of multi-component glass or the like. Various plastics such as silicone resin, fluorine-containing resin, and polyurethane are used for the plastic cladding.

The plastic cladding 2A at the tip of the large-diameter optical fiber 2 is removed with a solvent such as alcohol, and the tip of the glass core 2B is reduced in diameter to form a reduced-diameter core 5. The small diameter optical fiber 3 also has a plastic cladding 3A at its tip.
has been removed.

Then, the end face of the reduced diameter core 5 and the end face of the glass core 3B are connected by a known fusion bonding means to form a fusion splicing portion 6. Note that, in order to reduce optical loss, it is preferable that the end surface diameter of the reduced diameter core 5 and the end surface diameter of the glass core 3B be approximately equal.

The reduced diameter core 5, the fusion splice 6, and the exposed portions of the large-diameter optical fiber 2 and the small-diameter optical fiber 3 are coated with a material such as silicone resin, fluorine-containing resin, or polyurethane, which has approximately the same function as a plastic cladding. be done.

In the connecting section 1 of different diameter optical fibers having the above configuration, the light from the large diameter optical fiber 2 is sequentially narrowed down and condensed by the reduced diameter core section 5, and then enters the small diameter optical fiber 3. do. Conversely, when light enters the large-diameter optical fiber 2 from the small-diameter optical fiber 3, its path is sequentially expanded by the diameter-reduced core portion 5. In the latter case as well as in the former case, the reduced diameter core portion 5 sequentially focuses the light along a smooth reflection path.
The degree of light loss due to transmission out of the core beyond the critical angle is reduced. Particularly in the latter case, that is, when light enters the large diameter optical fiber 2 from the small diameter optical fiber 3, there is almost no optical loss.

Next, a method for manufacturing the connecting portion 1 of optical fibers with different diameters will be explained with reference to FIG.

In FIG. 2(a), the tip of the plastic cladding 2A is removed, leaving the tip of the glass core 2B exposed. Next, in FIG. 2(b), the tip of the glass core 2B is pushed into the container 9 filled with hydrofluoric acid 8 step by step at predetermined time intervals, and since it dissolves more than the tip that has been immersed for a longer time, Figure 2 (c)
A reduced diameter core 5 whose diameter is reduced in stages as shown in FIG. In addition,
A method of sequentially pushing the material into the container 9 is preferable to a method of immersing the material into the container 9 and then pulling it up sequentially. That is, the generation of etching pits that tend to occur at the interface between hydrofluoric acid and air can be prevented by sequential pressing.

Next, in FIG. 2(d), the plastic cladding 3A at the tip of the small diameter optical fiber is removed, and the glass core 3B is removed.
The tip is exposed. The end surface of the glass core 3B and the end surface of the reduced diameter core 5 are fused and connected so as to be concentric with each other to form a connecting portion 6. Next, as shown in FIG. 2(e), the reduced diameter core 5, the fusion splice 6, and the exposed portions of the large diameter optical fiber 2 and the small diameter optical fiber 3 are coated with silicone resin, fluorine-containing resin,
Covered with a material equivalent to plastic cladding such as polyurethane.

By the way, the shape of the diameter-reduced core 5 is not limited to the stepwise diameter-reduction shape, and there are various shapes such as a conical diameter reduction shape. Its form can be changed in various ways by appropriately selecting the relationship between the immersion time in hydrofluoric acid and the immersion length. That is, in FIG. 3, OA→
Stepwise dipping of B-+C results in a stepwise diameter-reduced core.

However, if the dipping is carried out linearly at a constant speed like 0→A-B-+D, a substantially conical diameter-reduced core is obtained. Further, if the dipping is performed slowly at the beginning and end and quickly at the middle, as in the case of 0→A→B−+E, a reduced diameter core with a concave center and a smooth connecting portion can be obtained. In order to reduce light loss, it is preferable to make the scent profile as loose and smooth as possible, but from the viewpoint of manufacturing, it is easy to reduce the diameter in stages.

By the manufacturing method explained above, a large-diameter optical fiber with a core diameter of 800 tt- is connected to a small-diameter optical fiber with a core diameter of 20 Qu. Optical loss was measured at the connection. The optical loss when light enters the small diameter optical fiber from the large diameter optical fiber is 11 dB or less, which is smaller than that using the ferrule described in FIG. 4. Further, the optical loss when light entered from the small diameter optical fiber to the large diameter optical fiber was less than IdB, which was good with almost no optical loss.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

In the connecting section of different diameter optical fibers of the present invention, the cladding of the large diameter optical fiber is removed and the tips of the cores are sequentially compressed at the connecting force section of two plastic clad glass core optical fibers having different core diameters. The end face of a small diameter optical fiber whose diameter has been increased and the cladding at the end portion removed is fusion spliced to the reduced diameter end face of the large diameter optical fiber, and the cladding removed portion of the spliced portion is recoated with a material equivalent to the cladding. Even when light enters from a large-diameter optical fiber to a small-diameter optical fiber, the light passes along a smooth reflection path through the reduced-diameter core, reducing optical loss and simplifying the structure. It can be mass-produced at a low price. As a result, it becomes possible to transmit long distances using a small diameter optical fiber connected to a large diameter optical fiber, which reduces the cost of the entire transmission system by using low cost small diameter optical fibers and low cost connections. For example, it can be used in Taiyo Kou's automatic concentrating and transmitting equipment.

The manufacturing method involves sequentially pressing the core tip of the large-diameter optical fiber after the cladding has been removed into phthalic acid, and by controlling the speed of pressing, etc., a desired diameter-reduced shape can be obtained. Since it can be obtained reliably and easily, it becomes possible to mass-produce products at low cost.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the connecting portion of different diameter optical fibers, Fig. 2 is a diagram showing the manufacturing process of the connecting portion of different types of optical fibers, and Fig. 3 is a graph showing the manufacturing process of reduced diameter cores of various shapes. FIG. 4 is a sectional view showing a conventional connecting portion of different types of optical fibers. The explanations of the main symbols in the figure are as follows. 1... Connection portion of different types of optical fibers, 2... Large diameter optical fiber, 2A... Plastic clad, 2B... Glass core, 3... Small diameter optical fiber, 3A... Plastic clad, 3 B -...Glass core, 5...Reduced diameter core, 6...Fusion splicing part, 7...Coating part, 8...Hydrofluoric acid.

Claims (2)

[Claims] (1) At the connection point between two thick and thin plastic clad glass core optical fibers with different core diameters, the cladding of the large diameter optical fiber was removed, the tip of the core was sequentially reduced in diameter, and the cladding at the end was removed. 1. A splicing section for optical fibers of different diameters, characterized in that an end face of a small-diameter optical fiber is fusion-spliced to a reduced-diameter end face of the large-diameter optical fiber, and a portion of the spliced part from which the cladding has been removed is re-coated with a material equivalent to the cladding. (2) The method for manufacturing a connecting portion of a different diameter optical fiber according to claim 1, wherein the reduced diameter core is formed by sequentially pushing the tip of the core into hydrofluoric acid after removing the cladding.