JPS587966B2 - Hikari Densouyo Glass Fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for connecting glass fibers for optical transmission.

In the field of optical communications, connecting glass fibers for optical transmission is a practically important issue.

Conventionally, the following three methods have been considered for connecting glass fibers for optical transmission: (i) connecting fibers in a ■-shaped groove; (ii) connecting fibers within a sleeve; and (iii) connectors.

However, these methods have advantages and disadvantages.

For example, the disadvantage of (1) is that there are restrictions on the materials in which the V-shaped groove can be formed, and it is particularly difficult to form highly accurate ■-shaped grooves on glass materials; There is a difference between the inner diameter of the sleeve and the outer diameter of the fiber, and a perfect match cannot be obtained. It becomes necessary.

In addition, conventionally, in addition to this, Fig. 1 a to d and Fig. 2 a,
A connection method as shown in b has also been proposed.

In Figures 1 a to d, 1 is porous glass that shrinks when heated, 2 is a hole provided in porous glass 1, A, B are fibers, 3A, 3B, 3 are cladding, 4
A, 4B, 4 are cores, and 5 is a heater.

Here, porous glass refers to U.S. Patent No. 3,859,0
73 and No. 3,864,113, and may be a porous glass made by appropriate soot generation conditions by flame hydrolysis.
It may be a porous glass made by the process of melting a phase-splitting glass, separating the phase by heat treatment, and removing a soluble portion by leaching, as known by Vycoh et al.

In short, any material that shrinks significantly when heated at high temperatures is sufficient.

Further, the holes 2 are formed by inserting a refractory material when soot is generated or melted and pulling out the refractory material when the glass is completed, or after the porous glass is produced.

Further, the shape of the hole 2 is preferably circular or polygonal.

Figures 1a, b, and c show that fibers A and B, each having a transmission core of 4A and 4B and a cladding of 3A and 3B, are inserted into the holes 2 of the porous glass 1 made in this manner and are butted together. ing.

Note that this porous glass adsorbs a large amount of moisture on its surface, so for example, in the case of borosilicate glass, the moisture content is 200 to 30%.
It is necessary to use a material that has been treated at an appropriate temperature such as 0° C. and then placed in a low moisture atmosphere such as a vacuum atmosphere after the treatment.

FIG. 1d shows the set prepared as shown in FIG. 1a being heated to a high temperature by a heater 5 to shrink and crush the hole 2 shown in FIG. 1a.

This heater may be an electric furnace, a flame, or anything else.

For example, SiO2 15%, B2O3 30%, Na2O
When porous glass made by melting → phase separation → elution of borosilicate glass with a composition of 5% was gradually heated to 300℃ and held for about 4 hours, it was heated to a high temperature of 900 to 1150℃. By doing this, the 15th to 35th sections also contract.

As porous glass shrinks in this way, fiber A,
B is fixed with its end faces abutting each other.

When heating at this high temperature, attention must be paid to the fact that the strength of the fiber generally weakens when the surface is exposed to high temperatures.

For example, the surface of the fiber that is not covered by the porous glass should not be heated to too high a temperature.

In FIGS. 2a and 2b, a porous glass 2 with a refractive index close to that of the optically active portion is used.

In this case, a thin glass portion 2 having a refractive index similar to that of the cores 24A and 24B is formed between the fibers A and B.
You can also put 6 in between.

In a variation of this method, only the thin layer of glass 26 is
The refractive index of the core portion is the same as that of the core portion, and the other portions may be made of a different porous glass.

The connection methods shown in Figures 1a to d and Figures 2a and b use porous glass to connect the fibers, so the lifespan of the connections can be extended even in hot locations. (because the expansion coefficients of the fiber and porous glass can be made almost equal), and the structure of the connection part can be simplified and miniaturized. However, it is possible to simply shrink the porous glass. Since the fibers are connected by the same method, there are problems with the strength and reliability of the connection part.

The present invention has improved the above-mentioned drawbacks, and its purpose is to improve the strength and reliability of the connection.

Examples will be described in detail below. FIGS. 3A to 3D are explanatory diagrams of an embodiment of the present invention, and the following description will be made with reference to FIGS. 3A to 3D.

First, the glass fibers 31A, B are made of a glass that is easy to weld with the glass of the fibers and the porous glass 33, has a low melting temperature, and, if necessary, has a refractive index similar to that of the photoactive portion in the fiber. Insert it into the pipe 32 consisting of.

(Fig. 3 a or b) These are placed in a pipe 33 made of porous glass and heated.

A hole 34 may be provided in which the necessary glass 32 melts and melts.

(FIG. 3C) As a result of heating, the porous glass 33 contracts and becomes as shown in FIG. 3D.

In these methods, it is also possible to use various combinations of tapered pipes made of porous glass.

Furthermore, other glass powder or the like having a coefficient of expansion close to that of these glasses may be packed between the porous glass and the fibers.

Alternatively, the entire porous glass may be molded with resin or the like.

In the explanations so far, the connection of individual fibers has been explained, but these connection methods are also possible even if a large number of holes are provided in the porous glass.

Next, examples of the present invention will be described using specific numerical values.

StO2 55%, GeO2 10%, B2 O3 27%
, 6% Na2O, and 2% Al2O3 was melted at 1400°C, and this glass was wound around a 600μmφ platinum wire to make a 5mmφ thick rod.
After that, the platinum was pulled out and the inner diameter was 600μmφ and the outer diameter was 5m.
A porous glass tube with a diameter of 200 mm and a length of 200 mm was prepared.

This porous glass tube was heat-treated at 550° C. for 50 hours to cause phase separation, and then eluted with 3N-HCI (100° C.) to make it porous.

This bolus glass tube was gradually heated to 300'C to dehydrate it.

Next, B2 O3 20%, Ge O2 20%, SiO2
Created by melting and spinning 60% glass, inner diameter 150 μmφ, outer diameter 500 μmφ, length 1
A 00 mm glass tube was placed inside the porous glass tube.

Next, two fibers each having a diameter of 130 μm were inserted into the glass tube and brought together.

Next, the outside of this porous glass tube was heated to 1100° C. to shrink it.

At this time, the B2O3-GeO2-SiO2 glass melted and flowed out through the pores of the porous glass tube.

Very good results were obtained, with a transmission loss of 0.2 dB at the connection location of the fiber made in this manner.

As explained above, the present invention provides a method for connecting fibers inserted into holes provided in porous glass and porous glass.
A glass layer with a low melting temperature that is easy to weld with fibers is provided, and then the porous glass is heated.
When heated, the glass layer melts and fuses with the fibers to weld them together, so compared to the conventional method shown in FIGS. 1a to d and 2a and b, the connection part It has the advantage of improving reliability and strength.

[Brief explanation of the drawing]

1A to 1D and 2A and 2B are explanatory diagrams of a conventional example, and FIGS. 3A to 3D are explanatory diagrams of an embodiment of the present invention. A, B, 31A, 31B are fibers, 1, 21, 33
is porous glass, and 2 and 34 are holes. 3A, 3B, 3, 23
A, 23B is clad, 4A, 4B, 4, 24A, 24
B is a core, 5, 25, 35 are heaters, 26 is a glass membrane,
32 is a glass pipe.

Claims (1)

[Claims] 1. Two optical transmission glass fibers are arranged in abutted relation to each other in a hole provided in the porous glass, and the optical transmission glass fiber is welded between the porous glass and the optical transmission glass fiber. A glass layer having a low melting temperature that is easy to melt is provided, and then the outer periphery of the porous glass is heated to melt the glass layer, shrink the porous glass, and fix the optical transmission glass fiber. A unique method for connecting glass fibers for optical transmission.