JPS58184905A - Production of single polarization optical fiber - Google Patents

Abstract

PURPOSE:To prevent the deterioration in polarization characteristics owing to oscillation, bending and twisting by forming a secondary coating layer of a thermoplastic resin continuously by extrusion coating on the outside circumferential surface of a primarily coated single mode optical fiber which is beforehand formed while said fiber is kept applied with required twisting. CONSTITUTION:A single mode optical fiber strand 1 which is produced by coating the strand with a silicone resin is let off from a rotary spool 3 and is passed through the inside of a feed capstan 4, a wire twister 5 and a resin extrusion coater 6 and is then taken up on a take-up drum 7. The strand is passed through the inside of the twister 5 under adjustment of the revolution of the capstan 4 and the drum 7 to apply twisting continuously on the primarily coated fiber 1 which is then fed into the coater 6. The fiber which is formed with a secondary coating layer consisting of a thermoplastic resin such as nylon on the outside surface by extrusion coating is taken up on the drum 7. The single polarization optical fiber 2 having the stable twisted construction and the desired polarization characteristics is obtained by the above-mentioned method.

Description

[Detailed description of the invention] 1) Technical field of the invention The present invention relates to a method for manufacturing a single polarization optical fiber that can transmit linearly polarized light over long distances with low loss. ■) Prior art and problems Conventionally, In single-mode optical fibers used for optical communications, the linearly polarized plane of propagating light can freely swing or rotate, or change to elliptically polarized waves, due to bending, vibration, external pressure, etc. of the optical fiber. Although this phenomenon is observed, it does not change the total amount of transmitted light, so it is not a major problem for general optical communication transmission lines. However, on the other hand, in recent years, with the aim of effectively utilizing the polarization plane of transmitted light,
A single-polarized optical fiber that can transmit linearly polarized light without rotationally changing the polarization plane of the propagating light has been developed, and has been applied to the field of measurement technology that utilizes optical phenomena such as single light, light phase, and light interference. is being attempted.

By the way, the above-mentioned conventional single polarization optical fiber has, for example, a core and a cladding having a concentric cross-sectional shape to form an optical waveguide section, and the outer periphery of the optical waveguide section is surrounded by an elliptical second cladding and a circular support layer. A configuration in which the outer periphery of an optical waveguide consisting of a concentric elliptical core and a cladding is surrounded by a circular second cladding and a U-circular support layer is known, and these optical fibers In both cases, an anisotropic strain is applied to the core from the vertical and lateral directions by the strain applying section composed of the second cushion and the support layer, and the transmission is possible without changing the polarization characteristics of linearly polarized light. A structure has been adopted that allows for However, when manufacturing an optical fiber having such a structure, there is a manufacturing problem in that it is not easy to form the cross-sectional shape of the optical waveguide consisting of the former second clad or the latter core and cutlas into a desired elliptical shape. be.

Mayu:Although the single-polarized optical fiber having the above-mentioned configuration has excellent polarization characteristics against vibrations, bending, etc., it has the disadvantage that the polarization characteristics deteriorate significantly against twisting. There is a need for a method that can easily manufacture a single polarization optical fiber without deterioration of polarization characteristics due to twisting.

((3) Purpose of the Invention The present invention was made in view of the above-mentioned conventional situation, and its purpose is to improve polarization characteristics caused by vibration, bending, and torsion by adding twist to a conventional single mode optical fiber. Focusing on the well-known technology that can transmit linearly polarized light without rotationally changing the plane of polarization, which eliminates deterioration in polarization, we developed a new manufacturing method that can form such single-polarized optical fibers with a stable twisted structure in one process. The purpose is to provide a method.

(4) Structure and purpose of the invention: 1. If the present invention is incorporated, a secondary coated single mode optical fiber made of a thermoplastic resin is attached to the outer circumferential surface of a pre-formed primary coated single mode optical fiber with a required twist. This is accomplished by providing an l-adic process for single polarization optical fibers characterized by continuous extrusion coating of coating layers.

(e) Examples of the invention Examples of the manufacturing method according to the invention will be described in detail below with reference to the drawings.

The figure is a schematic diagram showing an embodiment of the apparatus and process applied to the method of manufacturing a single-polarized optical fiber according to the present invention. First, through the normal optical fiber manufacturing process, the outer diameter is 12 mm.
A single mode optical fiber strand l (hereinafter abbreviated as a second coated fiber) was made by spinning a 5 μm single mode optical fiber and coating the outer circumference with silicone resin so that the outer diameter was 300 μm. , wind it up on Nupoo/I/3. Next, after placing the sprue /I/8 in a rotating means (not shown), the primary coated fiber is fed out from the rotating swab /I/8, and the feeding capstan 4 is moved as shown in the figure.
．． The wire rod is arranged in a wire twisting machine 5 and an extruded resin coating device 6 in such a manner that it is passed through and wound onto a winding drum 7. Then, by adjusting the rotation of the pre-delivery capstan and the winding drum 7, the primary coated fiber 1 is fed out from the rotating gear 3 at a feed rate of, for example, 80 rnt/min.
The secondary coated fiber l is passed through the wire twisting machine to continuously add a twist of, for example, 600 rad/mt, and the primary coated fiber l with such twist is continuously extruded into a resin coating device. A secondary coating layer made of a thermoplastic resin such as nylon is coated on the outer peripheral surface by extrusion to a thickness of, for example, 300 μm, and the winding drum 7
Take up one roll in sequence. In this case, instead of the twisting machine 5, the winding drum 7 or the pulley 3 may be rotated on an axis perpendicular to their long axes to impart twist. By such a manufacturing method, a single polarization optical fiber 2 having a stable twisted structure and desired polarization characteristics is produced.
can be easily obtained.

(1) Effects of the Invention As is clear from the above explanation, the manufacturing method according to the present invention allows simple twisting without using a special process such as forming the core part or the strain application layer in an elliptical shape as in the past. By applying a primary coating through the process and adding a twist to the single-mode optical fiber, the outer peripheral surface is extruded and coated with a thermoplastic resin, thereby ensuring that the polarization characteristics do not deteriorate due to vibration, bending, or twisting. It has the advantage of being able to easily and inexpensively obtain a single polarization optical fiber, and has excellent effects when used.

[Brief explanation of drawings]

The figure is an explanatory diagram conceptually showing an example of mounting applied to the method for manufacturing a single-polarized optical fiber according to the present invention. In the figure, l is a primary coated single mode optical fiber, 2 is a single polarized optical fiber, 3 is a rotating spool, 4 is a feeding capstan, 5 is a wire twisting machine, 6 is an extrusion resin coating device, and 7 is a winding device. Showing the drum.

Claims (1)

[Claims] A unit characterized in that a pre-formed primary coated single mode optical fiber is given a required twist, and a secondary coating layer consisting of 25 islands of thermoplastic resin is continuously extruded and coated on the outer peripheral surface of the fiber. A method for manufacturing a monopolarized optical fiber.