JPS5938702A - Pipe covered optical fiber - Google Patents

Abstract

PURPOSE:To obtain each kind of characteristics, by forming two-layer structure of pipes of different materials in pipe coated type optical fiber. CONSTITUTION:A quartz type optical fiber 1 is provided with a primary coating layer 2 and a secondary coating layer 3 on its circumference and both are made of silicone type resins, the layer 3 being harder than the layer 2. The pipe 4 is composed of inner and outer layers 5, 6, covering the optical fiber 1. A viscous agent 7 contained between the layers 3, 5 is a liquid, such as petroleum type gelly, Si oil, or paraffin. The layer 5 is made of a thermoplastic resin, such as polycarbonate or methacrylate resin, and has high Young's modulus, superior mechanical characteristics, such as tensile strength, and advantages, such as oil resistance and low cost. The outer layer 6 is made of thermoplastic synthetic resin, such as fluorinated resin (polytetrafluoroethylene), polyacetal, polyacrylate, chlorinated polyether, or nylon, and it has high resistance to chemicals.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in pipe coated optical fibers.

Pipe coated optical fiber, which is a type of optical fiber, is
An optical fiber on which a primary coat (primary coating layer) and a buffer coat (buffer layer) have been formed is housed in a synthetic resin pipe, and a liquid or sherry-like substance is formed between the outer circumference of the optical fiber and the inner circumference of the pipe. A viscous material is interposed.

This pipe coated optical fiber has longer optical fiber than the pipe, and the optical fiber is flexible and is housed in a large bend without micropends, so it has excellent tensile resistance and lateral pressure resistance. There are various properties that should improve the protection effect of optical fibers, such as buffering properties, and obtain low-loss transmission characteristics.

One of the important matters regarding pipe-coated optical fibers is the remaining length ratio, which is determined by the relative relationship between the pipe length tp) and the optical fiber length tf), which is (lf'-tp)/
t p

What is also important is the outer diameter and wall thickness of the pipe, and the outer diameter and wall thickness of the pipe are set as small as possible.

First, from the perspective of increasing the allowable elongation, the larger the gap between the outer periphery of the optical fiber and the inner periphery of the pipe, the better; The smaller the outer diameter, the better. Therefore, in pipe-covered optical fibers, the outer diameter and wall thickness of the pipe are set small to satisfy these points.

By the way, the resin for constructing the above pipe is as follows:
Various resins have been adopted, but there are few resins that satisfy pipe formability, high Young's modulus with elongation at break of 80% or more, and low cost. When considering oil resistance and chemical resistance in relation to chemicals used for stripping fibers when connecting them, there is no resin that has all of these properties, and therefore conventional pipe-coated optical fibers cannot be used. However, at least one or more of the above-mentioned characteristics are lacking, which poses a problem.

In view of the above-mentioned problems with pipe-coated optical fibers, the present invention provides a pipe with a two-layer structure made of different materials so that various characteristics can be obtained. This is explained by:

In Figure 1, (11 has a primary coating layer (2) on its outer periphery.
This is a quartz-based optical fiber in which a buffer layer (3) and a buffer layer (3) are formed, and both of these layers (2+ +3) are made of silicone resin, for example, and the buffer layer (3) is made of a primary coating layer (2+). ) is harder.

In this case, if the buffer layer (3) also serves as the primary coating layer (2), the layer (2) is omitted.

(4) is a pipe that houses the coated optical fiber (1), and the pipe (4), which consists of an inner lit (5) and an outer layer (6), is made of various materials described below.

(7) is a viscous material interposed between the outer periphery of the optical fiber (1) and the inner periphery of the pipe (4), and this viscous material (7) is made of a liquid material such as petroleum-based shuri, silicone oil, paraffin, etc. .

Next, to explain the materials constituting the inner layer (5) and outer layer (6) of the pipe (4), both the inner layer (5) and the outer layer (6) are made of thermoplastic synthetic resin. The quality is different from each other, and furthermore, both layers (51 + 6
1 are in close contact with each other, but are not chemically bonded.

Specific examples of the thermoplastic synthetic resin constituting the inner layer (5) include polycarbonate and methacrylic resin, and the inner layer (5) is made of any resin selected from these.

The advantages of the resin constituting the inner layer (5) are that it has a high Young's modulus and excellent mechanical properties against tension, good moldability, 111i1 oiliness, and low cost. On the other hand, the disadvantage is that it can cause deterioration such as clouding, devitrification, cracking, and swelling against chemicals such as acetone and toluene used for stripping when connecting optical fibers; It has no chemical properties.

A specific example of the thermoplastic synthetic resin constituting the outer layer (6) is a fluorine-based resin (ethylene tetrafluoride ethylene polymer).
ET F F ), polyacetal, chlorinated polyether, polyacrylate, nylon (nylon 12), etc., and the outer layer (6) is made of any resin selected from these.

The resin used for the outer layer (6) has disadvantages such as lower mechanical properties, poor moldability, lack of oil resistance, and high cost compared to the resin for the inner layer (51). However, it is characterized by high chemical resistance against acetone, toluene, etc. mentioned above.

Furthermore, in the relative relationship between both +m +5+ +6+, the coefficient of thermal expansion of the inner layer (5) is small, whereas the coefficient of thermal expansion of the outer layer (6) is quite large. When the outer layer (6) is formed, the outer layer (6) will shrink at a large shrinkage rate, and the shrinkage force at this time acts not only in the radial direction of the inner layer (5) but also in its longitudinal direction, so that the inner layer ( 5) shrinks in the longitudinal direction in a state that exceeds its own shrinkage rate〇 Pipe (4) consisting of the above inner layer (5) and outer layer (6)
The thickness of the outer layer (6) is about 400 μm, and the thickness of the outer layer (6) is set to be from several tens of μm to several hundred μm. However, the outer layer (6) is formed thinner than the inner layer (5). It's good to be there.

Next, a manufacturing example of the pipe-coated optical fiber according to the present invention will be briefly explained with reference to the second drawing.

In Figure 2, the primary coating layer (
2) and the buffer layer (3) is unwound and the optical fiber [11] enters the interior of a hollow nipple OD housed in the crosshead OQ of the extruder (9).

A supply device 0z for the viscous material (7) is connected to the hollow nipple (11), which is provided with a sealing means at the entrance for entering the optical fiber, and the number inside the nipple D is the supply device ( A viscous material (7) is supplied via I3.

On the other hand, the thermoplastic resin constituting the inner layer (5) is supplied to the resin flow path in the crosshead 00) of the extruder (9), and the resin is distributed between the outer periphery of the nipple tip and the inside of the die in the crosshead 00). The inner layer (5) is extruded into a pipe shape.

Therefore, when the optical fiber (11) passes through the extruder (9), a vibrator-shaped inner layer (5) is formed on its outer periphery.
A viscous phase (7) is interposed between the inner circumference of the inner layer (5) and the outer circumference of the optical fiber (1).

After passing through the extruder (9), the optical fiber (1) with the inner layer (5) on the outer periphery passes through the cooling tank (131), where the inner layer (5) is cooled to a predetermined temperature, and then the inner layer (5) The optical fiber tl+ with ) enters the extruder U51 via the capstan U41.

The optical fiber +1+ with the inner layer (5) is transferred to the next extruder (
151 and passes through its crosshead a, the extruder α5 is supplied with the thermoplastic resin constituting the outer layer (6), and therefore this extruder (Iω
In the optical fiber with an inner layer aω passing through (1), an outer layer (6) is formed around the outer periphery of the inner layer (5) 0, that is,
The remainder of the pipe (4) is formed by the second extrusion coating means, thereby obtaining a predetermined /< Eve coated optical fiber. After the outer layer (6) is cooled to a predetermined temperature, it is wound onto a winder via a capstan α8).

Note that the resin constituting the outer layer (6) has a high shrinkage rate, so when it is cooled in the cooling tank q7, the outer layer (6) shrinks considerably in the radial and longitudinal directions. The outer layer (6) is in close contact with the inner layer (5) and applies its longitudinal contraction force to the same layer (5), so that the inner layer (5)
is forcibly contracted through the outer layer (6).

Optical fiber with a small coefficient of linear expansion and almost no expansion or contraction (1)
On the other hand, the contraction of the pipe (4) consisting of the inner layer (5) and the outer layer (6) results in an extra length of the optical fiber (1), and the shrinkage rate The surplus length ratio can be controlled by appropriately setting the wall thickness ratio of the outer layer (6) with a large shrinkage rate and the inner layer (5) with a small shrinkage rate.

As explained above, the present invention provides a pipe covering in which an optical fiber having a buffer layer on the outer periphery is housed in a synthetic resin pipe, and a viscous material is interposed between the outer periphery of the optical fiber and the inner periphery of the pipe. In the type optical fiber, the pipe is composed of an inner layer and an outer layer, and the inner layer is made of a material that is superior in oil resistance and mechanical properties and inferior in chemical resistance,
The outer layer is characterized by being composed of 411 carbon fibers which have superior chemical resistance.

Therefore, in the case of the present invention, unlike pipes made of a single material, each material is used in the right place to form the inner and outer layers. All the same characteristics can be ensured, and since the inner layer can be made of inexpensive materials instead of only being made of expensive materials, the cost increase factor can be alleviated.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of a pipe-covered optical fiber according to the present invention, and FIG. 2 is an explanatory diagram schematically showing an example of manufacturing the pipe-covered optical fiber. (1)...Optical fiber (2)...Primary coating layer (3)...Buffer layer (4)...Pipe (5)...Inner layer (6)... Outer layer (force... Viscous material patent applicant agent Patent attorney Makoto Ito

Claims (1)

[Claims] (11) A pipe coating in which an optical fiber having a buffer layer on its outer periphery is housed in a synthetic resin pipe, and a viscous material is interposed between the outer periphery of the optical fiber and the inner periphery of the pipe. type optical fiber, the pipe consists of an inner layer and an outer layer,
A pipe-coated optical fiber in which the inner layer is made of a material that has superior oil resistance and mechanical properties, but recessive chemical resistance, and the outer layer is made of a material that has dominant chemical resistance. (2) The pipe-covered optical fiber according to claim 1, wherein the inner and outer layers of the pipe are made of extruded thermoplastic synthetic resin. (3) The pipe covering type according to claim 2, wherein the extrusion shrinkage rate of the thermoplastic synthetic resin constituting the inner layer of the pipe is smaller than that of the thermoplastic synthetic resin constituting the outer layer of the pipe. optical fiber. (4) The pipe-covered optical fiber according to any one of claims 1 to 3, wherein the inner layer and outer layer of the pipe are not chemically bonded.