JPH01219802A - Manufacture of optical fiber core - Google Patents

Abstract

PURPOSE:To remove the unevenness of the peripheral surface of a core and to reduce optical transmission loss by drawing a core forming polymer together with a plastic hollow body while charging the core forming polymer in the plastic hollow body. CONSTITUTION:While the core forming polymer 2a is charged in the plastic hollow body 1a before or after the plastic hollow body 1a is hardened, the core forming polymer 2a is drawn axially together with the plastic hollow body 1a, and then the core forming polymer is cross-linked with the core forming polymer. Consequently, even if the inner peripheral surface of the plastic hollow body 1a has unevenness, the unevenness of the inner peripheral surface is drawn sufficiently to eliminate projections and recesses, so the unevenness of the peripheral surface of the core forming polymer 2a which contacts the inner peripheral surface of the plastic hollow body 1a is removed effectively to reduce the optical transmission loss greatly.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing an optical fiber core made of an elastomer exhibiting rubber-like elasticity, which can effectively reduce optical transmission loss.

(Prior Art) A conventionally known method for manufacturing an optical fiber core made of an elastomer that exhibits rubber-like elasticity through crosslinking is disclosed, for example, in Japanese Patent Laid-Open No. 61-55611.

This method involves injecting a liquid transparent material that exhibits rubber-like elasticity after hardening into the space of a flexible hollow tubular body, and then hardening the transparent material to form a core. It becomes possible to manufacture optical fiber cores at low cost.

(Problem to be Solved by the Invention) However, in such conventional techniques, the presence of irregularities on the inner circumferential surface of the flexible hollow tubular body, which is formed by extrusion molding in most cases, creates a problem in the space. Since unevenness is also formed on the circumferential surface of the core that is heated and hardened, there is a problem in that the optical transmission loss becomes considerably large. Since the core is formed only by curing, there are problems in that it is extremely difficult to manufacture a narrow core and it is also impossible to manufacture a long core.

In order to solve this problem with the prior art, a method has been proposed in which an elastomer optical fiber core is manufactured by flowing a liquid polymer for core formation through an extrusion die and crosslinking the liquid polymer during the flow. Although this method has the advantage of effectively removing irregularities on the peripheral surface of the core and making it possible to manufacture small diameter cores and long cores relatively easily, it is difficult to use liquid polymers. In relation to viscosity, flow conditions, etc.
Another problem was that it was extremely difficult to maintain the diameter of the core at a predetermined value over its entire length, as well as to properly control the core diameter.

The present invention advantageously solves these problems of the prior art, and allows the core diameter to be made substantially uniform over its entire length while sufficiently removing irregularities on the circumferential surface of the core. The present invention provides a method for manufacturing an optical fiber core in which the core diameter can be extremely easily controlled.

(Means for Solving the Problems) The method for manufacturing an optical fiber core of the present invention particularly includes:
Before or after the plastic hollow body is cured, the core forming polymer is stretched in the axial direction together with the plastic hollow body while the inside thereof is filled with the core forming polymer, and then the core forming polymer is crosslinked. It is.

(Function) According to this method, even if the plastic hollow body that functions like a core mold has irregularities on its inner peripheral surface, the core-forming polymer can be filled into the inside of the hollow plastic body.
By stretching a plastic hollow body, the unevenness existing on its inner circumferential surface is sufficiently stretched, and both the valleys and peaks are almost or completely erased. The unevenness is also very effectively removed from the peripheral surface of the core-forming polymer that contacts the inner peripheral surface of the core, and as a result, optical transmission loss is significantly reduced compared to the prior art.

Also here, by stretching the plastic hollow body and the core-forming polymer by means of a drawing die or other action, the core diameter can be precisely maintained at a predetermined value over its entire length, and the core diameter can be adjusted very easily. It can be any required value.

(Example) The present invention will be explained below based on illustrated examples.

FIG. 1 is a process diagram showing one embodiment of the present invention.
Figure 1a shows a pre-shaped plastic hollow body having the required inner diameter and length.

Here, this plastic hollow body is made of thermoplastics such as polyethylene, polypropylene, ethylene-propylene copolymer, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, nylon, urethane, polyethylene terephthalate, etc. It can be constructed by forming it into a tubular shape by extrusion molding, and preferably, a mold release agent is applied to the inner circumferential surface of the tube in advance.

Figure 2 shows another example of such a plastic molded body.
It is shown in a perspective view with a part cut away, as shown in Figure 2(a).
The plastic hollow body 11a shown in FIG. It has a shape in which two tubular bodies each having a rectangular cross section are arranged laterally and integrated.

Both of these plastic hollow bodies 11a are shown here.

21a, although not shown, can also be applied to multiple structures having various other cross-sectional shapes in the same manner as shown in FIG. 1(a) in the steps described below.

Here, as shown in FIG. 1(b), such a plastic hollow body 1a is filled with a core forming polymer 2a without any gaps by a vacuum injection method, a pressure injection method, or the like.

In this way, as the core-forming polymer 2a filling the inside of the plastic hollow body 1a, butadiene polymer, fluorine polymer, siloxane polymer, etc. can be used, and among them, dimethylsiloxane polymer, phenyl group- or naphthyl group-containing polymer, etc. can be used. Preference is given to using siloxane polymers or compositions thereof.

In addition, various additives can be added to the core-forming polymer to give it a suitable curvature, and when it is crosslinked by heating, a crosslinking agent, a crosslinking catalyst, etc. can be added thereto. can also be added.

Thereafter, by using stretching rollers, shaping rollers, one or more drawing dies, etc., the core-forming polymer 2a is drawn together with the plastic hollow body 1a in a manner related to the inner diameter and length of the plastic hollow body 1a. As shown in Figure 1(C), the core-forming polymer 2a is stretched in the axial direction until it has a predetermined diameter and length, often to a length that is 10 times or more the original length. In addition, during such stretching, the plastic hollow body 1a is heated to an appropriate temperature depending on its material.

Furthermore, a stretched plastic hollow body 1b containing a stretched core-forming polymer 2b is provided for the crosslinking means, which can be a radiation source, an ultraviolet source, a heat source, etc.
By relatively displacing , from one end to the other,
The stretched core-forming polymer 2b is uniformly and sufficiently crosslinked over its entire length to form the required optical fiber core.

The optical fiber core manufactured in this manner is obtained by removing the stretched plastic hollow body 1b to form a single optical fiber core 2C as shown in FIG. By coating it with a clad using a known method, it can be used as an optical fiber. Here, the drawn plastic hollow body 1b can be removed by peeling, melting, dissolving, etc., and such removal can be done by applying a mold release agent to the inner peripheral surface of the plastic hollow body 1a. It becomes especially smooth.

Further, the cladding here can be formed of an elastomer or a non-elastomeric material, and the elastomeric cladding is preferably a crosslinked product of a liquid fluoropolymer, a fluorine-containing liquid siloxane polymer, or a liquid dimethylsiloxane polymer, and the non-elastomeric cladding is It is preferable to select polymethyl methacrylate, fluororesin, etc.

According to the optical fiber core manufactured as described above,
Even if the plastic hollow body 1a has unevenness on its inner peripheral surface, those unevenness can be almost or completely removed by converting the plastic hollow body 1a into the stretched plastic hollow body 1b. Therefore, the stretched core-forming polymer 2b is located inside the stretched plastic hollow body 1b and is regulated by the inner peripheral surface thereof.
Also, most or all of the irregularities will be removed from the circumferential surface. This results in a sufficiently smooth optical fiber core 2C and a significant reduction in optical transmission loss.

Moreover, here, by uniformly stretching the plastic hollow body 1a, the diameter of the optical fiber core 2c can be made substantially uniform over its entire length, and by simply adjusting the stretching rate, The core diameter can be controlled as desired.

In addition, according to this method, since the core-forming polymer 2a is injected into the plastic hollow body before stretching, the injection can be performed extremely easily and quickly.

FIG. 3 is a longitudinal sectional view showing another embodiment of the invention.

Here, by coextruding the core forming polymer 22a and the plastic hollow body forming polymer 23a from the core extrusion die 21 and the hollow body extrusion die 22, which are arranged concentrically with each other, an extruded core forming polymer 22b is produced. This is also a continuous rod-shaped body 24 enclosed in an extrusion-molded plastic hollow body 23b, and then
This rod-shaped body 24 is passed through a stretching device 25 and pulled out by a tension roller 26, thereby yielding a stretched structure 27 consisting of a stretched core-forming polymer 22c having a desired diameter and a stretched plastic hollow body 23c, Subsequently, the stretched structure 27 is passed through a crosslinking means 28 to continuously crosslink the stretched core-forming polymer 22C, thereby forming a long optical fiber core 22d exhibiting rubber-like elasticity.

And the optical fiber core 2 manufactured in this way
2d constitutes an optical fiber by removing the stretched plastic hollow body 23C and then applying a cladding to the peripheral surface thereof.

Optical fiber core 2 manufactured by such a method
2d can also have an extremely smooth peripheral surface by forming the continuous rod-shaped body 24 into a stretched structure 27 by the action of the stretching device 25, and can greatly reduce optical transmission loss.

A comparative example of optical transmission loss between an optical fiber core manufactured by the method of the present invention and an optical fiber core manufactured by a conventional method will be described below.

[Comparative example]

- Mono-addition reaction type phenylmethyl silicone rubber (phenyl group content 25%, viscosity approximately 30P) as an invention core forming polymer
) as a commercially available polyethylene tube (inner diameter 3.1φ, outer diameter 4.0φ, length 5m) as a plastic hollow body.
After being injected under reduced pressure, the polyethylene tube was drawn by passing it sequentially through five dies heated to about 80°C.

At this time, the inner diameter of the polyethylene tube, that is, the outer diameter of the core material, was 0.93 mm, and the stretching ratio was about 10 times.

Next, by post-vulcanizing this in an oven at 80°C for 1 hour, the phenylmethyl silicone rubber is crosslinked,
Further, by heat treatment in an oven at 180°C for 5 minutes, the phenylmethyl silicone rubber is secondary vulcanized, and at the same time, the polyethylene tube is melted and removed, resulting in a crosslinked elastomer optical fiber core with rubber-like elasticity of about 50 m. I got it.

Addition reaction type dimethyl silicone rubber (viscosity 30
Deep coating a cladding material consisting of P),
Thereafter, it was crosslinked in a heating furnace at 200°C to obtain an optical fiber.

The optical transmission loss of this optical fiber was measured and was approximately 50.
Ivy at 0 dB/km.

The time required to inject the core-forming polymer into the polyethylene tube as a hollow plastic body was 2 minutes.
It was 5m.

・Conventional product Phenylmethyl silicone rubber similar to that used in the invention product is injected under reduced pressure into a commercially available polyethylene tube (inner diameter 1φ, outer diameter 2φ, length 5m), and then post-vulcanization is performed in an oven at 80°C for 1 hour. The phenylmethyl silicone rubber is crosslinked by this process, and the phenylmethyl silicone rubber is further vulcanized by heat treatment for 5 minutes in an oven at 180°C, and the polyethylene tube is melted and removed to form a crosslinked rubber-like material. Obtain an elastic elastomer optical fiber core.

This core was coated with a cladding material in the same manner as the invention, and the cladding material was vulcanized to form an optical fiber.

The optical transmission loss of this optical fiber was measured and was approximately 70.
It was 00dB/km.

The time required to inject the core-forming polymer into the plastic hollow body was 1 hour and 15 m.

(Effects of the Invention) According to the present invention, in particular, the core-forming polymer is stretched together with the plastic hollow body while the inside of the plastic hollow body is filled with the core-forming polymer. It is possible to effectively remove surface irregularities and significantly reduce optical transmission loss, and to make the core diameter sufficiently uniform over the entire length of the core. Therefore, the core diameter can be controlled extremely easily.

[Brief explanation of the drawing]

Fig. 1 is a process diagram showing an embodiment of this invention, Fig. 2 is a perspective view showing another example of a plastic hollow body with a part cut away, and Fig. 3 shows another embodiment of this invention. FIG. la, 23b...plastic hollow body 1b, 23
c...Stretched plastic hollow body 2a, 22a...
Core forming polymers 2b, 22c...Stretched core forming polymers 2C, 22d...Optical fiber core 22b...Extruded core forming polymer 23a.
...Plastic hollow body forming polymer patent applicant Brideston Co., Ltd. Figure 1

Claims (1)

[Scope of Claims] 1. In manufacturing an optical fiber core made of an elastomer that exhibits rubber-like elasticity through crosslinking, the core-forming polymer is inserted into the plastic hollow body while the core-forming polymer is filled inside the plastic hollow body. 1. A method for producing an optical fiber core, which comprises stretching the core together with the core, and then crosslinking the core-forming polymer.