JPS6381306A - Optical fiber core and its production - Google Patents

Abstract

PURPOSE:To decrease an optical transmission loss and an increase in the loss by a temp. change by forming a protective coating layer consisting of a thermoplastic resin formed on an optical fiber strand in a manner as to have compressive strain. CONSTITUTION:The thermoplastic resin 4 flows a double pipe flow passage between a die 1 and a nipple 2 and the thermoplastic resin is coated on the optical fiber strand 3 where the strand emits from the nipple 2. The thermoplastic resin 4 is extrusion-coated under pressurization on the optical fiber strand 3 at the amt. required for coating said thermoplastic resin on the optical fiber strand to the outside diameter which is the same as the bore of the nozzle of the die 1 or the amt. in excess thereof as the output of the above-mentioned resin. Since the thermoplastic resin 4 coated on the optical fiber strand 3 is molded while the resin is held pressurized in the longitudinal direction of the optical fiber, the shrinkage of the coating to be generated right after the extrusion coating and after heat history does not grow to the shrinkage rate to the extent of generating microbending in the optical fiber strand and rather acts in the direction to elongate the optical fiber. The transmission characteristic of the optical fiber is thereby improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical fiber core wire in which a protective coating layer is provided on an optical fiber wire and a method for manufacturing the same, and particularly relates to a core wire and a method for manufacturing the same. It comes out.

[Conventional technology]

Conventional methods for manufacturing this type of optical fiber have all adopted a method called chain extrusion molding, also known as vibe molding or draw-down molding, to extrude and coat the optical fiber with thermoplastic resin. There is. FIG. 2 is a diagram illustrating the main parts of a coating section for carrying out conventional extrusion molding of a thermoplastic resin-coated chip. In other words, the thermoplastic resin 4, such as nylon, is drawn down so that the thickness of the coating on the t1 optical fiber 3 is smaller than the thickness of the flow in the double pipe channel of the die 1 for forming the coating. An extrusion coating method has been adopted. 2 is a nipple for extrusion molding of the tip.

[Problem that the invention seeks to solve]

In the conventional coating method using chip extrusion molding in the production of optical fiber cores, when extrusion coating a thermoplastic resin onto an optical fiber strand, the thermoplastic resin is coated on the optical fiber strand while being pulled. As a result, the optical fiber is shrunk in the longitudinal direction due to molding shrinkage when the thermoplastic resin cools, or dimensional changes that occur when molding residual strain due to the orientation of the thermoplastic resin during extrusion coating is relaxed. As a result, the optical fiber is bent at an extremely small period, so-called microbending, which tends to increase optical transmission loss. In addition, optical fiber cores suffer from thermal history after being coated.
As a result of the further relaxation of the molding residual strain and the simultaneous progress of crystallization, there is a problem in that the coating shrinks and the temperature characteristics of optical transmission loss deteriorate.

[Means for solving problems]

The present invention solves the conventional problems and provides a coated optical fiber and a method for manufacturing the same that reduce optical transmission loss and increase in loss due to temperature changes. The protective coating layer is characterized in that it has a compressive strain structure, and the step of forming the compressive strain protective coating layer of the present invention on an optical fiber strand is performed using a die for pressure extrusion molding. Using a nipple, in particular, with the outlet tip of the nipple located within the nozzle of the die, extrude the amount of thermoplastic resin necessary to apply a coating with an outer diameter that is equal to or greater than the nozzle diameter of the die. It is characterized by extrusion coating.

[Effect]

The present invention covers the optical fiber by extruding thermoplastic resin under pressure with the outlet terminal of the nipple for pressure extrusion molding positioned in the nozzle of the die. The thermoplastic resin is molded under pressure in the longitudinal direction of the optical fiber, so even if molding shrinkage occurs after cooling, it is mainly due to radial shrinkage.
The dimensional change in the longitudinal direction is extremely small and does not generate enough contractile force to cause microbending in the optical fiber. In addition, since the optical fiber is oriented in the thermoradial direction during extrusion coating and the degree of orientation is minute, the optical fiber will hardly shrink in the longitudinal direction due to relaxation of residual strain, but will rather elongate. Furthermore, when optical fibers are subjected to thermal history after coating, even if molding residual strain is relaxed and crystallization progresses, the resulting shrinkage of the coating is much smaller than in the conventional draw-down method using tube extrusion. It is small and will actually expand rather than shrink.

For the above reasons, since the present invention is a method of coating a thermoplastic resin on an optical fiber by a pressure extrusion method, the shrinkage of the coating that occurs immediately after extrusion coating and after thermal history is Micro-bending of the optical fiber does not result in any amount of contraction, but rather works in the direction of stretching the optical fiber, so the optical transmission characteristics of the optical fiber can be significantly improved. Examples will be described below based on the factors.

〔Example〕

The figure explaining the main part of the covering part which performs extrusion molding is shown.

1 is a die for pressure extrusion molding, 2 is a nipple, an optical fiber element Hs is passed through the center of the nipple 2 in the direction of the arrow, and the double pipe flow path between the die 1 and the nipple 2 is heated. The plastic resin 4 flows in the same direction as the optical fiber 5, and when the optical fiber 5 exits the nipple 2, the optical fiber 3
is coated with thermoplastic resin. At this time, thermoplastic resin 4
The extrusion amount C is doubled by pressurizing and extruding the amount required to coat the optical fiber strand 3 with the same outer diameter as the nozzle diameter of the die 1, or an amount exceeding that amount. Inside the tube flow path, the thermoplastic resin 4 is in a pressurized state, and as a result, the outer diameter of the optical fiber core extruded from the die 1 is the same as that of the die 1 immediately after exiting the nozzle of the die 1. It has an outer diameter that is the same as or exceeds the nozzle diameter.

As a result, since the thermoplastic resin 4 coated on the optical fiber element I13 is molded under pressure in the longitudinal direction of the optical fiber, even if molding shrinkage occurs after cooling, the thermoplastic resin 4 is The contraction of the optical fiber in the radial direction is rough, and the dimensional change in the longitudinal direction does not generate enough contraction force to cause microbending in the optical fiber strand 3. In addition, the black bean m-type resin 40 orientation during pressure extrusion coating is also oriented in the radial direction in the longitudinal direction of the Hikari 7 fiber, and the degree of orientation is minute, so there is almost no contraction in the longitudinal direction due to relaxation of residual strain. In fact, it will grow.

Furthermore, even if the residual strain of the thermoplastic resin 4 is relaxed and crystallization progresses when it is subjected to thermal history after coating, the resulting shrinkage of the coating is extremely small compared to conventional draw-down molding. It will grow longer.

As is clear from the above reasons, when coating an optical fiber with a thermoplastic resin using the pressure extrusion method of the present invention, shrinkage of the coating that occurs immediately after extrusion coating and after thermal history causes micro-bends on the fiber optic fiber. Since the generation of de-ing does not lead to any amount of contraction, but rather works in the direction of stretching the optical fiber, it is possible to significantly improve the transmission characteristics of the optical fiber.

Next, a heat cycle test was conducted on an example of an optical fiber core 111 prototyped according to the present invention and a comparative example of an optical fiber core 111 manufactured by conventional draw-down molding, and the results of nine experiments will be described.

Nylon 12 (for example, Diamid Z, -16
EXAMPLE 40 Daicel Chemical Co., Ltd. was extruded and coated using a pressure extrusion method to produce an optical fiber core of an example of the present invention having an outer diameter of α9. At this time, the diameter of the die used for pressure extrusion molding was 0.9*mφ, the diameter of the nipple was α40qn, the diameter of one dowel was 511 mm, and the drawdown rate was 1.0. The present example O optical fiber core and the comparative example optical fiber core manufactured by conventional tube extrusion at, -so°C to +80°C.
A heat cycle test was conducted for 10 cycles in a temperature range of 6C. The following figure shows the heat cycle test results of an example of the present invention and a conventional comparative example.

As is clear from the heat cycle test results in the above equation,
The Hikari 7 fiber core wire coated with thermoplastic resin by pressure extrusion molding of the present invention has less influence on the optical fiber due to coating deformation than optical fiber core wires manufactured by conventional chain extrusion molding, and is resistant to temperature changes. It has stable optical transmission characteristics.

〔Effect of the invention〕

As explained above, in the conventional optical fiber manufacturing method in which the optical fiber core is coated with a black bean-based resin through the extrusion molding, the optical fiber is In contrast, the pressure extrusion method of the present invention allows the black bean-breathable resin to be made into light. The manufacturing method of the optical fiber coated wire coated on the fiber wire reduces the optical transmission loss of the optical fiber by suppressing the shrinkage of the thermoplastic resin coating in the longitudinal direction, and also reduces the optical transmission loss of the optical fiber due to temperature changes. It is possible to achieve a reduction, and the effect is large.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the main part of a pressure extrusion molding of a thermoplastic resin coating according to the present invention, and FIG. 2 is a diagram of the main part of a conventional chain extrusion molding of a thermoplastic resin coating. 1... Dice 2... Nipple 3... Optical fiber strand 4... Kuromame Arashi Resin Patent Applicant Sumitomo Electric Industries, Ltd. (RIH) Representative Patent Attorney Hisashi Tamamushi Five Departments Regarding the Invention Figure 1s1 shows the configuration of the main parts of pressure extrusion molding of the thermoplastic resin coating. Figure 1s2 shows the construction of the main parts of the conventional chinibu extrusion molding of the thermoplastic resin coating.

Claims (4)

[Claims] (1) An optical fiber core in which a protective coating layer made of a thermoplastic resin is applied to the outer periphery of the optical fiber strand by melt extrusion, wherein the protective coating layer has compressive strain. line. (2) A method for manufacturing an optical fiber coated wire, in which a thermoplastic resin is melt-extruded on the outer periphery of the optical fiber strand to apply a protective coating layer to form an optical fiber coated wire, wherein the thermoplastic resin is melt-extruded and a protective coating layer is applied. The process includes: forming a protective coating layer having compressive strain by pressurizing and extruding the thermoplastic resin using a pressurizing extrusion die and a nipple; Method. (3) In the step of pressure extrusion molding the thermoplastic resin, the thermoplastic resin is 3. A method for producing a coated optical fiber according to claim 2, which comprises extruding. (4) Pressure extrusion molding the thermoplastic resin includes coating the optical fiber with an outer diameter equal to or larger than the nozzle diameter of the pressure extrusion die. 3. The method of manufacturing a coated optical fiber according to claim 2, wherein the thermoplastic resin is extruded and coated with a required extrusion amount.