JP2007121725A - Method of manufacturing plastic optical fiber cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a plastic multi-fiber optical fiber cable, with which a proper cable of eccentricity can manufactured easily, while preventing increase in the transmission loss, without damaging plastic optical fibers when covering a coating layer. <P>SOLUTION: In the method of manufacturing the plastic multi-fiber optical fiber cable, which uses a coating extruder with a cross head and coats outer peripheries of two or more plastic optical fibers with a thermoplastic resin to integrate them into a single body, distance L2 from a front end of a nipple to a discharge face of a die in the cross head is within a range from 1/3×L1 to 4/5×L1, where L1 is the land length of the die. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plastic optical fiber cable used as an optical signal transmission wiring.

  Plastic optical fibers have already been put into practical use for short-distance data communication applications and sensor applications. At that time, the plastic optical fiber is rarely used only, and is used as a plastic optical fiber cable in which a coating layer made of a thermoplastic resin is provided on the outside. Further, such plastic optical fiber cables are often used in the form of multi-core plastic optical fiber cables in which two or more plastic optical fibers are arranged in parallel on the same surface.

  Here, the coating layer of the multi-core plastic optical fiber cable is generally provided using a coating extruder with a crosshead. However, when coating a plurality of plastic optical fibers with a coating resin, there is a problem in that the plastic optical fibers are damaged and transmission loss is increased. At the same time, when manufacturing such a multi-core plastic optical fiber cable, there has been a problem that the central axis of each fiber is biased to one side. The eccentricity of such a plastic optical fiber cable is generally adjusted by adjusting the structure and arrangement of the dies / nipples in the crosshead, but in order to obtain a product with good eccentricity. However, it was necessary to repeatedly produce the dice / nipple having a very complicated structure and the above adjustment.

  By the way, as a method of forming a coating layer of an optical fiber, Patent Document 1 discloses an extruder for coating an optical fiber in which a nipple tip portion is positioned in a die nozzle. It is described that it is possible to prevent a decrease in strength of the optical fiber by using. Patent Document 2 discloses a method of manufacturing a plastic optical fiber cord using a coating apparatus having a specific relationship in nozzle length and diameter, and describes that deterioration of loss during coating processing can be prevented. Yes.

JP 60-131852 A Japanese Patent Laid-Open No. 03-296007

  However, the die nozzle described in Patent Document 1 does not have a structure that can sufficiently prevent an increase in power loss when used for coating a plastic optical fiber, and the die nozzle described in Patent Document 2 has a nipple tip. Since the portion overlaps with the inflow portion of the coating resin, there is a risk that the fiber is damaged during coating and the loss increases.

  It is an object of the present invention to prevent an increase in transmission loss without damaging a plastic optical fiber when a coating layer is coated, and to easily manufacture a cable having a good eccentricity. It is to provide a method for manufacturing a cable.

The present invention relates to a method for producing a multi-core plastic optical fiber cable, in which the outer periphery of two or more plastic optical fiber wires is coated with a thermoplastic resin and integrally formed using a coated extruder with a cross head. The present invention relates to a method for manufacturing a multi-core plastic optical fiber cable, wherein the land length of the inner die is L1, and the distance L2 between the tip of the nipple and the discharge surface of the die is in the range of the following formula (1).

1/3 × L1 <L2 <4/5 × L1 (1)

Here, in the manufacturing method of the multicore plastic optical fiber cable of the present invention, when the outer diameter of the plastic optical fiber is D1 and the inner diameter of the nipple is D2, D1 and D2 satisfy the following formula (2). Is preferred.

1.04 × D1 <D2 <1.3 × D1 (2)

Furthermore, in the method for producing a multi-core plastic optical fiber cable according to the present invention, it is preferable that the following formula (3) is satisfied in the nipple die for compounding the coating resin at an angle θ with respect to the nipple central axis.

10 ° <θ ≦ 45 ° (3)

  In the manufacturing method of the multicore plastic optical fiber cable of the present invention, as the plastic optical fiber to be used, one having a known structure can be used. For example, it has a core-sheath structure and the refractive index change is stepped. SI-type optical fiber that changes in shape, GI-type optical fiber in which the refractive index of the core gradually decreases from the center toward the outer periphery, and a plurality of islands are integrated with a common sea part separated from each other Examples include multi-core optical fibers. Here, all of the plurality of plastic optical fibers forming the multi-core plastic optical fiber cable may be the same type of plastic optical fiber or a combination of different types of plastic optical fibers.

  A known thermoplastic resin used as a coating material for the plastic optical fiber can be selected for the coating layer used in the method for producing the multicore plastic optical fiber of the present invention. Examples thereof include polyethylene, polyvinyl chloride, polyurethane, polyamide 11, polyamide 12, chlorinated polyethylene, and polyolefin elastomer.

Here, as a coating apparatus for forming the coating layer of the plastic optical fiber, a general coating extruder with a crosshead is used. As shown in FIG. 1, the crosshead which is a main part of the coating apparatus is used. Dies and nipples are provided. In a cross head having such a die / nipple structure, a tube portion through which a strand passes (hereinafter, this tube portion is referred to as a “corner”) is provided at the tip of the nipple. It is arranged on the same axis. This corner protrudes into the die land, and the tip of the corner is at a position L2 from the die discharge surface. The melted coating material is extruded into the gap between the die and the nipple, and is coated on the outer periphery of the strand when it comes out from the corner of the nipple tip. This coating position is rectified in the running direction of the wire while the coating material is pushed out through the gap between the die land and the nipple angle. By rectifying in this way, the coating material is coated in a state of being in close contact with the outer periphery of the strand. Here, by making this L2 within a specific range in relation to the die land length L1, damage to the plastic optical fiber during coating, eccentricity, and adhesion between the plastic optical fiber and the coating material are improved. it can. L2 is the length of the die land as L1,
1/3 × L1 <L2 <4/5 × L1
The range. Preferably
5/12 × L1 <L2 <7/10 × L1
By making it in such a range, the plastic optical fiber is not scratched, and an increase in transmission loss can be prevented. Furthermore, the plastic optical fiber is positioned at the center of the die land axis, and the eccentricity is also good.

  When L2 is 4/5 × L1 or more, the plastic optical fiber is pushed toward the center axis of the die / nipple by the coating material, and the transmission loss increases due to the outer periphery of the plastic optical fiber being scratched by the inner wall surface of the nipple hole. In addition, the eccentricity is also deteriorated.

  If L2 is 1/3 × L1 or less, a gap is generated between the coating material and the outer periphery of the plastic optical fiber, and the thickness variation of the coating layer and the adhesion between the coating material and the plastic optical fiber are not preferable.

  The nipple diameter D2 through which the plastic optical fiber passes is that the plastic optical fiber is scratched due to the workability of passing the plastic optical fiber through the nipple hole at the start of the coating operation, and the outer diameter fluctuation and rolling of the plastic optical fiber itself. In order to prevent this, it is preferable that 1.04 × D1 <D2. More preferably, 1.05 × D1 <D2.

  In addition, when the coating material leaves the tip along the outer periphery of the corner and is coated onto the plastic optical fiber, if the outer diameter D3 of the corner is large, a gap is generated between the plastic optical fiber and the coating layer at the corner tip, and the strand and the coating are formed. The layers may not adhere to each other or the thickness of the coating layer may vary. Further, the coating material is liable to stay at the corner tip. Therefore, D3 is preferably D3 <2.0 × D2. More preferably, D3 <1.6 × D2.

  On the other hand, 1.3 × D2 <D3 is preferable from the viewpoint of mechanical strength of the corners. From the appropriate range of D3, the nipple diameter D2 is preferably D2 <1.3 × D1, more preferably D2 <1.2 × D1.

  Here, as shown in FIG. 1, the coating material is extruded into the gap between the corner of the nipple and the die land at an angle of θ (°) with respect to the central axis of the nipple, and is coated on the plastic optical fiber. As described above, since the coating resin flowing through the gap between the nipple angle and the die land just before coating is preferably rectified, the smaller the θ is, the smaller the flow of the coating material flowing into the gap between the nipple angle and the die land is. It is rectified without difficulty. For these reasons, θ is preferably 45 ° or less, and more preferably 35 ° or less. Further, when θ is 10 ° or less, the die nipple becomes long and is difficult to be prepared for the crosshead. Therefore, it is preferably larger than 10 °, more preferably larger than 15 °.

Hereinafter, the present invention will be described with specific examples.

[Example 1] Preparation and evaluation of two-core plastic optical fiber cable Two plastic optical fibers (SK40 manufactured by Mitsubishi Rayon Co., Ltd.) were prepared, and a low-density polyethylene resin was used as a coating material. Using the dice / nipples shown in Table 1, the coating resin temperature was 155 ° C., the running speed of the strand was 40 m / min, and the first strand was coated with a low-density polyethylene resin, and the minor axis 2.2 mm An eyeglass-type two-core cable having a long diameter of 4.4 mm was obtained.
The obtained plastic optical fiber cable showed no scratches on the fiber surface, and the transmission loss of the two plastic optical fibers was 138 dB / km and 137 dB / km, respectively. Further, when the cable cross section was observed, no eccentricity was observed, which was good.

[Example 2]
A glasses-type two-core cable was obtained in the same manner as in Example 1 except that the inflow angle θ of the resin was 30 °. The obtained results are shown in Table 1.

Example 3
A glasses-type balanced four-core cable was obtained in the same manner as in Example 1 except that four plastic optical fibers (SK40 manufactured by Mitsubishi Rayon Co., Ltd.) were used. The obtained results are shown in Table 1.

(Comparative Example 1)
A glasses-type two-core plastic optical fiber cable was obtained in the same manner as in Example 1 except that a nipple without a corner was used at the tip of the nipple. When the surface of the obtained cable was observed, scratches were generated in the longitudinal direction, and the transmission loss was 142 dB / km and 153 dB / km. Further, when the cross section of the cable was observed, the two fibers were fixed in the center, and the eccentricity was remarkably deteriorated.

[Comparative Example 2]
A glasses-type two-core plastic optical fiber cable was obtained in the same manner as in Example 1 except that a die / nipple having L1 of 5 mm and L2 of 0.5 mm was used. The adhesion of the obtained cable covering material was poor, and the transmission loss of the plastic optical fiber was large. Moreover, the outer diameter fluctuation of the cable was also large.

It is sectional drawing of the nipple / die structure of the coating | coated apparatus which manufactures a plastic optical fiber cable.

Claims (3)

In a method of manufacturing a multi-core plastic optical fiber cable in which the outer periphery of two or more plastic optical fiber wires is coated and integrated with a thermoplastic resin using a coating extruder with a cross head, A method for producing a multi-core plastic optical fiber cable, wherein the land length is L1, and the distance L2 between the tip of the nipple and the discharge surface of the die is in the range of the following formula (1).

1/3 × L1 <L2 <4/5 × L1 (1)
The multi-core plastic optical fiber cable according to claim 1, wherein D1 and D2 satisfy the following formula (2), where D1 is an outer diameter of the plastic optical fiber and D2 is an inner diameter of the nipple. Method

1.04 × D1 <D2 <1.3 × D1 (2)
3. The method for producing a multi-core plastic optical fiber cable according to claim 1, wherein an inflow angle θ (°) of the thermoplastic resin with respect to a nipple central axis is in the range of the following formula (3).
10 ° <θ ≦ 45 ° (3)

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