JPH0727927A - Production of liquid core optical fiber - Google Patents

Abstract

PURPOSE:To freely design the shape of an optical fiber and to decrease the thickness of a clad layer by forming a transparent layer as the clad layer of the optical fiber on the inner surface of a pipe or tube. CONSTITUTION:A transparent layer 2 is formed on the inner surface of a pipe 1 of any form. In this case, the transparent layer is obtd. by coating the inner surface of the pipe 1 with a resin soln. and hardening the resin. Then, the one end of the pipe 1 is sealed with a transparent plug 4, the inside of the pipe 1 is filled with a transparent liquid 3, and the other end is sealed with a transparent plug 4. By using a hardening-type liquid as the transparent liquid, the core liquid can be hardened, or instead of the transparent liquid, a transparent rod may be inserted. By this method, a clad layer can be formed for a pipe of any form. Further, any of metal pipes or plastic pipes can be used and the shape of the pipe is not specified but may be a circle or square, or with large diameter or small diameter, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid core optical fiber, and more particularly to a method of manufacturing a liquid core optical fiber used for optical energy transmission.

[0002]

2. Description of the Related Art A liquid core optical fiber (see FIGS. 3 and 4) in which a low refractive index transparent plastic pipe or tube is used as a cladding material and a transparent liquid is used as a core has been used up to now (hereinafter, simply referred to as a pipe). The pipe and the tube shall be collectively referred to even when stated). Fluorine resins such as FEP and PFA (both having a refractive index of 1.33) have been mainly used for the pipes used as the cladding material of these optical fibers in view of the refractive index. These resins are crystalline and therefore have a rather poor transparency, and a thick resin has a drawback of being cloudy, and a completely transparent fluororesin has been demanded.

In general, these fluororesins are thermoplastic resins and are characterized by having a very high melting point. When processing a fluororesin, it is common to heat it to 300 ° C. or higher and then extrude it into a pipe, and it is difficult to process it by another method. In extrusion molding, there are restrictions on the shape, size and wall thickness of the pipe.
There was a drawback that it was difficult to obtain an arbitrary pipe. Further, the FEP and PFA tubes currently on the market have a thickness of 1 mm or more, and consume a lot of materials. Since the material cost of the fluororesin is high, the price of the molded pipe is very high, which is a drawback. Further, a material having a low hardness such as silicone rubber cannot obtain sufficient strength as a pipe and is difficult to use as a clad material.

It is a necessary condition that the transparent liquid has a higher refractive index than the pipe to be used. For example, an aqueous solution obtained by adding sodium chloride or potassium chloride to water, an organic solvent such as ethylene glycol, a polymer such as silicone oil, etc. It is used.

An optical fiber can be obtained by putting a transparent liquid in a pipe serving as a clad material and plugging both ends with transparent windows. The material of the plug is transparent and it is required that its refractive index is close to that of the liquid serving as the core, but a rod or plate made of quartz glass, optical glass, PMMA resin or the like is used.

[0006]

In the conventional liquid core optical fiber, a transparent low refractive index plastic pipe or tube is used as a clad material. However, due to restrictions in manufacturing the plastic pipe, the pipe shape and pipe There was a limit to the size. Further, since the clad material is formed into a pipe, it is necessary to use a pipe that is mechanically strong and has a certain thickness to obtain sufficient strength as a pipe. Could not be used. Further, in the conventional liquid core optical fiber, since the clad material is thick, the amount of the material used is large and the cost is high.

[0007]

SUMMARY OF THE INVENTION The present invention relates to any material,
By forming a transparent layer that can serve as a clad layer of an optical fiber on the inner surface of a shaped pipe or tube, it becomes possible to obtain a liquid core optical fiber having a shape that cannot be obtained by the conventional extrusion molding method. Further, since the inner surface of the pipe is coated, the coating layer can be made of a material having low strength, and can be a thin film.

As a method for forming the transparent layer on the inner surface of the pipe or tube, the transparent resin is obtained by coating the liquid resin before curing in the pipe and curing it. Silicone resin as a transparent liquid resin,
Acrylic resins, fluorine-containing silicone resins, fluorine-containing acrylic resins, etc. are widely known. After coating the inner surface of the pipe with these resins, they are cured by heat curing or light curing to obtain a transparent layer. Recently, an amorphous perfluoro fluorine resin (Teflon AF: manufactured by DuPont, Cytop: manufactured by Asahi Glass Co., Ltd.) having properties similar to those of FEP and PFA resins has been developed. Since it is amorphous, it has excellent transparency and a refractive index of 1.33 or less. These resins are special perfluorinated solvents (Fluorinert: Sumitomo 3M)
It is possible to dissolve it in, and after forming a solution, a pipe is coated and the solvent is evaporated to obtain a clad layer similar to FEP and PFA.

The material of the pipe or tube by the above method is not particularly limited and can be freely selected, and the cladding layer can be formed in any shape of pipe. Metal pipes, plastic pipes, etc. can be used freely, and the shape is not particularly limited, such as circular, rectangular, large diameter, small diameter.

Since the clad layer is formed by solution coating, the thickness of the clad layer can be controlled from a very thin film to a sufficient thickness by controlling the coating thickness. In particular, thin films can be easily made, so less material is consumed,
It is possible to provide an inexpensive liquid core optical fiber with low manufacturing cost. After forming the clad layer in the pipe, the core liquid is filled. Examples of the core liquid include transparent organic solvents, transparent liquid polymers and aqueous solutions.

[0011]

The outline of the present invention is shown in FIGS. The transparent layer 2 is formed on the inner surface of the pipe 1 having an arbitrary shape. The forming method is not particularly limited, but there is a method of obtaining a transparent layer by coating a resin solution on the inner surface of the pipe and then curing the solution. Then, one end of the pipe is sealed with a transparent plug 4, the inside of the pipe is filled with the transparent liquid 3, and the other end is sealed with the transparent plug 4. By using a curable liquid as the transparent liquid,
It is also possible to cure the core liquid. Alternatively, it is possible to insert a transparent rod instead of the transparent liquid. In this way, a large-diameter optical fiber can be easily manufactured.

[0012]

【Example】

[Example 1] A silicon resin (made by Shin-Etsu Chemical: brand name OF) in a copper pipe (outer diameter 8 mm, inner diameter 6 mm, length 30 m)
106, refractive index 1.41, viscosity 2000 cps), and then silicone resin was poured out. The silicone resin remaining on the inner surface of the pipe is placed in a constant temperature bath at 150 ° C. and heated for 30 minutes.
A clad layer having a thickness of mm was formed.

A quartz glass plate (diameter 8 m) is attached to one end of the pipe.
m, thickness 2 mm) and sealed from the other end with ethylene glycol (refractive index 1.45). After fully filling the inside of the pipe and confirming that there were no bubbles, the other end was sealed with the same quartz glass plate. The liquid core optical fiber thus obtained was able to transmit sufficient light.

[Example 2] Fluorine-containing acrylate (made by Dainippon Ink Co., Ltd .: product name Defencer, refractive index 1.40) in a glass tube (outer diameter 30 mm, inner diameter 28 mm, length 2 m, refractive index 1.52). A viscosity of 1500 cps) was coated by dipping to a thickness of 0.2 mm. The coated fluorine-containing acrylate was cured by irradiating the glass tube with an ultraviolet irradiator (lamp, 3 kW, 80 W / cm ² ).

A quartz glass plate (diameter 30) is attached to one end of the glass tube.
mm, thickness 2 mm), and ethylene glycol (refractive index 1.45) was filled from the other end. After fully filling the inside of the pipe and confirming that there were no bubbles, the other end was sealed with the same quartz glass plate. The liquid core optical fiber thus obtained was able to transmit sufficient light.

Example 3 100 g of a transparent amorphous fluororesin (manufactured by Asahi Glass: trade name Cytop, refractive index: 1.34) was dissolved in 1000 g of a perfluoro solvent (Sumitomo 3M: trade name Fluorinert) to prepare a fluororesin. A solution was made. The fluororesin solution was poured into a urethane pipe (outer diameter 10 mm, inner diameter 8 mm, length 10 m) to uniformly coat the inner surface of the pipe. Then, it was dried at 100 ° C. for 24 hours to evaporate the solvent and form a transparent clad layer having a thickness of 0.05 mm.

One end of the glass tube was sealed with a quartz glass rod (diameter 8.5 mm, length 20 mm), and silicone oil (manufactured by Shin-Etsu Chemical: trade name Silicone HF, refractive index 1.41) was filled from the other end. . After fully filling the inside of the pipe and confirming that there were no bubbles, the other end was sealed with the same quartz glass rod. The liquid core optical fiber thus obtained was able to transmit sufficient light.

Example 4 100 g of a transparent amorphous fluororesin (made by Asahi Glass: trade name Cytop, refractive index 1.34) was dissolved in 1000 g of a perfluoro solvent (Sumitomo 3M: trade name Fluorinert) to give a fluororesin. A solution was made. The fluororesin solution was poured into a urethane pipe (outer diameter 10 mm, inner diameter 8 mm, length 10 m) to uniformly coat the inner surface of the pipe. Then, it was dried at 100 ° C. for 24 hours to evaporate the solvent and form a transparent clad layer having a thickness of 0.05 mm.

One end of the glass tube is sealed with a quartz glass rod (diameter 8.5 mm, length 20 mm), and the other end is covered with silicone resin (Shin-Etsu Chemical: trade name Silicone OF106,
The refractive index was 1.41). After fully filling the inside of the pipe and confirming that there were no bubbles, the pipe was heated at 80 ° C. for 5 hours to cure the silicone resin. Then, the other end was sealed with the same quartz glass rod. The liquid core optical fiber thus obtained was able to transmit sufficient light.

[0020]

According to the present invention, the manufacturing method of the liquid core optical fiber becomes easy. In addition, by selecting a base pipe that can use a soft and weak material such as silicone resin or rubber as the clad material, the shape of the optical fiber can be freely selected (large diameter, square, irregular shape). In addition, the thickness of the clad layer can be reduced, and the material cost can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view including an optical axis of a liquid core optical fiber according to the present invention.

FIG. 2 is a cross-sectional view perpendicular to the optical axis of the liquid core optical fiber according to the present invention.

FIG. 3 is a sectional view including an optical axis of a conventional liquid core optical fiber.

FIG. 4 is a sectional view of a conventional liquid core optical fiber perpendicular to the optical axis.

[Explanation of symbols]

 1: Pipe 2: Transparent layer 3: Transparent liquid 4: Transparent stopper 5: Transparent plastic pipe

Claims (3)

[Claims] 1. A liquid core light, comprising: forming a transparent layer capable of forming a clad for an optical fiber on the inner surface of a pipe or tube, and then enclosing a liquid inside the pipe or tube to form a core of the optical fiber. Fiber manufacturing method. 2. When forming a transparent layer that can be a clad on the inner surface of the pipe or tube of claim 1, a transparent liquid is coated on the inner surface of the pipe or tube and then cured to obtain a clad layer. Liquid core optical fiber manufacturing method. 3. A method of manufacturing a liquid core optical fiber according to claim 1, wherein an amorphous fluororesin is used as the transparent layer which becomes the clad.