JP2011123393A - Plastic clad optical fiber cord - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastic clad optical fiber cord in which reduction in transmission loss is small even when the plastic clad optical fiber cord is located under room heat environment. <P>SOLUTION: The plastic optical clad optical fiber cord includes: a plastic clad coated optical fiber in which a coating layer is formed on the coated optical fiber hardened by applying a clad agent made of a resin on a glass optical fiber; a tensile strength fiber layer disposed to surround the coated optical fiber; and an outer coat which is disposed surrounding the tensile strength fiber layer. A plasticizer is added to the outer coat. A moisture prevention layer exists inside the outer coat. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a plastic clad optical fiber cord.

  An example of a plastic clad optical fiber is disclosed in Patent Document 1. This document discloses that a flame retardant is added to a thermoplastic resin coated on the clad.

JP-A-7-209562 (particularly paragraph 0017)

  A resin to which a plasticizer such as polyvinyl chloride (PVC) is added may be used for a jacket of a plastic clad optical fiber (PCS) cord. In a humid heat environment, the plasticizer may be decomposed to generate alcohol having several to tens of carbon atoms. When this decomposition component moves to the cladding, the molecular motion of the cladding material becomes active, and the fluorine segments may aggregate. In this case, there is a phenomenon that the aggregated fluorine segment becomes a light scattering source and the transmission loss of signal light increases.

  The present invention prevents the plasticizer decomposition component in the jacket material from being transferred to the cladding by disposing a highly moisture-proof sheet around the optical fiber core wire. Another object of the present invention is to provide a plastic clad optical fiber cord with little increase in transmission loss even when placed in a humid heat environment.

A plastic clad optical fiber cord of the present invention includes a plastic clad optical fiber core, a tensile fiber layer disposed so as to surround the optical fiber core, and a jacket disposed around the tensile fiber layer. Is provided. A plasticizer is added to the jacket. There is a moisture-proof layer inside the jacket.
The moisture-proof layer preferably has a water vapor permeability of 0.08 g / m ² · 24 hours or less when the water vapor permeability is 40 ° C. and 90% RH.

  According to the present invention, a plastic clad optical fiber cord is provided which has little reduction in transmission loss even when placed in a humid heat environment.

It is sectional drawing which shows the plastic clad optical fiber cord of this invention. It is sectional drawing which shows another aspect of the plastic clad optical fiber cord of this invention. It is a conceptual diagram of the manufacturing method of the optical fiber strand used for the plastic clad optical fiber cord of this invention. It is a conceptual diagram of the manufacturing method of the optical fiber core wire used for the plastic clad optical fiber cord of this invention. It is a conceptual diagram of the manufacturing method of the plastic clad optical fiber cord of this invention. It is a conceptual diagram of the method of spirally winding the moisture-proof sheet of the plastic clad optical fiber cord of the present invention.

  As illustrated in FIG. 1, the plastic clad optical fiber cord 10 of the present invention includes a plastic clad optical fiber core wire 4, a moisture-proof layer 5 on the outer periphery thereof, a tensile strength layer 6 on the outer periphery thereof, and a jacket 7 on the outer periphery thereof.

The optical fiber core 4 includes a core 1, a clad 2 on the outer periphery thereof, and a coating 3 on the outer periphery thereof.
The core is made of quartz glass and has a diameter of 0.15-0.40 mm.
The clad is made of a fluorine-based resin, and its outer diameter is 0.20-0.45 mm. The thickness of the cladding is 15-50 μm. The fluororesin used for the clad includes fluorinated urethane (meth) acrylate.

  The coating is made of fluororesin and has an outer diameter of 0.5-0.7 mm. Examples of the fluororesin used for coating include polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA).

  The moisture-proof layer is made of a moisture-proof sheet and has a thickness of 0.04 mm to 0.30 mm. As the moisture-proof sheet, those marketed as moisture-proof sheets and moisture-proof films from film manufacturers (Toray, Kureha, Gunze, etc.) can be used. Examples of the material for the sheet include polyolefin resin, polyamide resin, polyimide resin, and polyester resin.

  The tensile strength layer is made of a tensile strength material such as an aramid fiber and has a thickness of 0.2 mm to 0.5 mm.

  The jacket is made of a polyolefin resin such as polyethylene (PE) or ethylene-vinyl acetate copolymer (EVA) or polyvinyl chloride (PVC) resin, and has an outer diameter of about 2.2 mm. The thickness of the outer jacket is appropriately adjusted so that the outer diameter becomes a predetermined value. A plasticizer is added to the jacket. Plasticizers include phthalate ester, phosphate ester, trimellitic ester, citrate ester, epoxy, and polyester plasticizers.

  A plastic clad optical fiber cord is provided with a tension member and a jacket around the core of the plastic clad optical fiber. The present invention is characterized by having a moisture-proof layer.

After placing a conventional plastic clad optical fiber cord in a humid heat environment, when the optical fiber cord was examined, volatile components such as alcohol (a few to a dozen carbon atoms) were detected from the clad. It is a component that is not originally contained in the clad, and is presumed to have migrated from the outside of the clad while in a moist heat environment. When the origin is obtained from this optical code, it is presumed that the plasticizer contained in the jacket is decomposed.
In the optical cord of the present invention, a moisture-proof layer is disposed on the inner side of the jacket and on the outer side of the clad to prevent the decomposition component of the plasticizer from being transferred to the clad. As a result, the fluorine segments do not aggregate in the cladding, and no signal light scattering source is generated in the cladding. That is, it is possible to prevent the transmission loss of signal light from deteriorating even when placed in a humid heat environment.
By providing the moisture-proof layer, transmission loss deterioration when placed in a humid heat environment is improved as compared with a conventional optical fiber cord having no moisture-proof layer. The higher the moisture-proof property of the moisture-proof layer, the smaller the amount of plasticizer that can be transferred, and the higher the effect of preventing transmission loss deterioration. If the moisture vapor transmission rate of the moisture-proof layer is 0.08 g / m ² · 24 hours or less at 40 ° C. and 90% RH, the deterioration of transmission loss is 5 dB / km or less. If this is the case, it can be said that there is no problem of transmission loss practically.

  The optical cord is provided with a tension member so that a large force is not applied to the optical fiber core wire even when the cord is pulled. As shown in FIG. 1, the moisture-proof layer can be provided inside the tensile body (immediately outside the optical fiber core wire), and can be provided outside the tensile body and inside the jacket as shown in FIG. In any case, the moisture-proof layer prevents the decomposition component of the plasticizer in the jacket from being transferred to the cladding.

  Optical fiber cords may be required to be flame retardant. In that case, a flame retardant is added to the jacket. Some flame retardants also act as plasticizers such as phosphate esters. The flame retardant decomposes in the same manner as a plasticizer in a moist heat environment to generate a volatile component. When this decomposition component (mainly alcohol) moves to the cladding, the problem of transmission loss deterioration occurs as described above. Since the optical fiber cord of the present invention has a moisture-proof layer, even if such a flame retardant is added to the jacket, it is possible to prevent transmission loss from deteriorating in a humid heat environment.

  In order to manufacture the optical fiber cord of the present invention, an optical fiber core is first manufactured, a tensile strength member is added thereto, a moisture-proof layer is further provided, and the jacket is covered. The order of the tensile strength layer and the moisture barrier layer may be reversed.

To manufacture an optical fiber core wire, first, an optical fiber preform is heated and drawn to form a glass strand. A clad material is applied to the glass element wire and cured. Subsequently, a coating material is applied and cured.
FIG. 3 shows a conceptual diagram of a method in which a clad material is applied to a glass element wire and cured. The optical fiber preform 21 is heated by a heating device 31 and drawn to obtain a glass strand 22. As the clad material, an ultraviolet curable resin added with a photopolymerization initiator is used. The clad material 23 is applied by passing the glass element wire 22 through the clad material 23 put in the coater 32. Thereafter, the clad material 23 is cured by irradiating the clad material 23 applied to the glass strand 22 with ultraviolet rays by the curing device 33. Fluorinated (meth) acrylate resin can be used for the clad material 23. In FIG. 3, when the clad material 23 is cured, it is taken up by the take-up device 34 and taken up by the take-up device 35. In FIG. 3, the direction of the optical fiber pass line is changed by the guide roller 36.
The coating provided on the clad is formed by extrusion coating with fluororesin (PTFE, ETFE, PFA, etc.). As shown in FIG. 4, the optical fiber 24 composed of the core and the clad is fed out from the feeding device 36, the fluororesin serving as the coating is pushed out by the cross head 37, and the coating layer is formed by water cooling with the cooling device 38. Then, the optical fiber core wire 4 is manufactured and wound by the winding device 39. A guide roller 48 is appropriately disposed on the pass line. Thus, an optical fiber core wire can be formed.

A moisture-proof sheet is wrapped around the optical fiber and sent further downstream. Downstream of that, a tensile body such as an aramid fiber is vertically attached to the optical fiber core, and the optical fiber core and the tensile body are pulled together. Downstream of that, the jacket is extrusion coated using a crosshead. The jacket is cooled by water cooling or the like, and the optical fiber cord is wound up.
The moisture-proof sheet may be wound either vertically (cigarette roll) or spirally. For vertical attachment, use a tapered tube. The diameter of the outlet of the cylinder is smaller than the diameter of the inlet, the diameter of the outlet is substantially equal to the outer diameter of the moisture-proof layer, and an optical fiber core is passed through the center of the cylinder so that the moisture-proof sheet is in contact with the inner surface of the cylinder By passing it through, the moisture-proof sheet can be rolled into a cigarette. In this case, the moisture-proof sheet has an overlapping portion. The width where the moisture-proof sheets overlap is about 10% or less of the outer periphery of the optical fiber core wire which is the inner layer. When winding in a spiral, use a bow that rotates around the path line of the optical fiber core, and let the moisture-proof sheet pass through a fixed point on the bow. It can be wound as supplied from the periphery of the fiber core. Even when wound in a spiral, the moisture-proof sheets are overlapped. The overlapping width is 1/6 to 2/3 of the width of the moisture-proof sheet.

FIG. 5 shows a conceptual diagram of a method for providing a moisture-proof layer, a tensile strength layer, and a jacket on the optical fiber core wire.
The optical fiber core wire 4 is fed out from the feeding device 40, the moisture proof sheet 25 is supplied from the moisture proof sheet supply device 41, and the moisture proof sheet 25 is wrapped around the optical fiber core wire 4 by the former 42 and vertically attached. If necessary, the moisture-proof sheet is pressed by a pressing roller 43 so as to be easily wound around the optical fiber core wire 4. Subsequently, the strength member 26 is supplied from the strength member supply device 44, and the strength member 26 is assembled around the optical fiber core wire around which the moisture-proof sheet is wound with the dice 45 and vertically attached. Subsequently, the outer cover resin is extruded by the cross head 46, and the outer cover is formed by water cooling with the cooling device 47, whereby the optical fiber cord 10 is manufactured. The optical fiber cord is wound around the winding device 49. A take-up device 50 is arranged on this pass line to take up the optical fiber core wire, the tensile body, and the moisture-proof sheet, and advance the pass line from upstream (left side in FIG. 5) to downstream (right side in FIG. 5). The number and positions of the take-up devices are not limited to the example shown in FIG. 5, and an appropriate number is arranged at an appropriate position. A guide roller 48 is appropriately disposed on the pass line.

  When spirally winding the moisture-proof sheet, the bow 51 is rotated about the optical fiber core wire 4 through the moisture-proof sheet through the passing point 52 of the bow 51 as shown in FIG. A location where the moisture-proof sheet is wound around the optical fiber core wire 4 is a die 53, which is a fixed point. A passing point 52 serving as a moisture-proof sheet supply point rotates around the optical fiber core 4, and the moisture-proof sheet is spirally wound around the optical fiber core 4. The moisture-proof sheet supply device 41 is arranged as close as possible to the rotation axis, that is, a position close to the optical fiber core 4, and the pressing member 54 is positioned as close to the optical fiber core wire 4 as possible between the moisture-proof sheet supply device 41 and the passing point 52. Arrange so that the path line length of the moisture-proof sheet is as constant as possible. In this way, the tension of the moisture-proof sheet is stabilized.

FIG. 5 shows an example in which the optical fiber cord is wound once after the coating of the optical fiber core wire is extruded, and then the optical fiber cord is manufactured. However, the winding process may be performed at other process breaks. For example, the film may be wound after the moisture-proof layer is wound or after a tensile body is added. However, the tensile strength body and the moisture barrier layer may be unwound when unrolled when they are unwound, so the winding of the moisture barrier layer, the vertical attachment of the tensile strength body, and the covering of the outer sheath as shown in FIG. It is preferable to carry out a series of flows without winding.
An optical fiber cord may be manufactured without winding once after manufacturing the optical fiber core 4.

When the moisture-proof layer is wound after the tensile body is attached to the optical fiber core wire, the moisture-proof sheet supply device 41, the former 42, the pressing roller 43, the tensile strength body supply device 44, and the die are applied in accordance with the cone wax example of FIG. 45 may be replaced, a tensile strength body is added first, and then a moisture-proof sheet is wound.

A plastic clad optical fiber having a core made of quartz glass and an outer diameter of 0.20 mm, a clad made of fluorinated urethane acrylate resin, an outer diameter of 0.23 mm, a coating made of ETFE, and an outer diameter of 0.50 mm Each optical fiber cord shown in Table 1 below is manufactured using the core wire. In each example, the outer diameter of the optical fiber cord is 2.2 mm.
The base resin of the jacket is PVC, and 5% by weight of a plasticizer and 5% by weight of a brominated flame retardant are added. This flame retardant also acts as a plasticizer.
After these optical fiber cords are placed in a humid heat environment of 70 ° C. and 85% relative humidity (RH) for 1000 hours, the transmission loss of signal light having a wavelength of 850 nm is measured.
The difference between the samples in each example is the presence or absence of the moisture-proof layer or the water vapor permeability or thickness of the moisture-proof layer. A comparative example is an example without a moisture-proof layer.

  By providing the moisture-proof layer, the transmission loss after being placed in a humid heat environment is improved. In particular, when the water vapor permeability of the moisture-proof layer is 0.08 g / m 2 · 24 hours or less at 40 ° C. and 90% RH, the transmission loss is sufficiently low, and there is no practical problem of transmission loss.

DESCRIPTION OF SYMBOLS 1 Core 2 Cladding 3 Coating | coated 4 Plastic clad optical fiber core wire 5 Moisture-proof layer 6 Tensile layer 7 Jacket | cover 10 Plastic clad optical fiber cord

Claims (2)

  A plastic clad optical fiber core, a tensile fiber layer disposed so as to surround the optical fiber core, and a jacket disposed around the tensile fiber layer, the plasticizer being disposed on the jacket A plastic clad optical fiber cord which has been added and has a moisture-proof layer inside the jacket ^2. The plastic clad optical fiber cord according to claim 1, wherein the moisture-proof layer has a water vapor permeability of 0.08 g / m ² · 24 hours or less at 40 ° C. and 90% RH.

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