JPH0446914B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to applications requiring heat resistance, such as power-optical composite cables such as OPGW, which have an extruded coating layer of a futuristic resin on a silicone layer. The present invention relates to a method for manufacturing a resin-coated quartz glass optical fiber suitable for

Conventional Technology Recently, various extrusion-moldable heat-resistant fluorocarbon resins have been developed. OPGW etc. are extrusion coated silica glass optical fibers with silicone layers. It is expected to be used in applications that require high heat resistance.

The optical fiber with the above structure is obtained by first applying a silicone layer on the optical fiber having a silica glass cladding layer, and then applying one type of fluorocarbon resin at a high temperature on the basis of its high melting point or high softening point. It is produced by extrusion followed by cooling the extruded coating layer.

Problems that need to be solved By the way, according to the conventional wisdom of coating optical fibers with organic polymers, extrusion coatings generally suffer from large molding distortions when rapidly cooled, causing microbends in the optical fibers. Since then, it has usually been slowly cooled. However, the fused silica glass optical fiber coated with a fluorine resin manufactured by this conventional method was tested in a 300°C instantaneous heat resistance test, which is one of the test items for heat-resistant optical fibers.
There is a problem in that a so-called spike phenomenon occurs, in which the transmission loss suddenly increases during the cooling process after heating to .degree.

Means for Solving the Problem The object of the present invention is to propose a method for manufacturing a resin-coated quartz glass optical fiber in which the spike phenomenon described above is not observed. That is, the present invention provides a silicone layer on a quartz glass optical fiber having a fused silica glass clad layer, extrusion coats a fluorocarbon resin on the silicone layer, and immediately after extrusion, applies an extrusion coating layer of the fluorocarbon resin. This is a method for manufacturing a resin-coated quartz glass optical fiber, which is characterized by rapid cooling.

Effect: By rapidly cooling the extruded coating layer of the fluorine-containing resin immediately after extrusion, the resulting optical fiber will not suffer from the spike phenomenon or its severity will be reduced.

Although it cannot be said that the reason why the spike phenomenon occurs has been clearly elucidated at present, the present inventors think as follows.

In other words, when the extruded layer is gradually cooled according to common sense, minute voids remain at the interface between the silicone layer and the extruded futuristic resin layer, and these voids remain during the heating-cooling process during the 300°C instantaneous heat resistance test. This causes rapid expansion and contraction in the optical fiber, which causes microbends in the optical fiber, and these microbands lead to the spike phenomenon.

On the other hand, by rapid cooling as in the present invention, no voids remain at the interface.

On the other hand, with regard to molding distortion due to rapid cooling of the extruded fluorine resin coating layer, which was a concern, there are some differences depending on the resin, but in general, the magnitude of molding distortion that occurs during rapid cooling is comparable to that during slow cooling. It was also found that there was no significant difference.

The present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a top view of an example of a production line for implementing the method of the present invention, and FIG. 2 is a cross-sectional structural diagram of an example of a resin-coated silica glass optical fiber manufactured by the method of the present invention. .

In FIG. 1, a silica glass optical fiber 2 coated with a silicone layer is sent out from a bobbin 1, and the fused silica resin is extruded and coated on the silicone layer by extrusion to the crosshead 4 of an extruder 3. The resin-coated quartz glass optical fiber thus produced is rapidly cooled in a water cooling device 5 installed immediately after the crosshead 4 and wound onto a bobbin 6.

In the present invention, as mentioned above, heat-resistant resins that can be extruded are used as the fluorocarbon resin, but among these, those that are particularly effective when adopted in the method of the present invention are tetrafluoroethylene, It is a perfluoroalkyl vinyl ether copolymer.

The distance between the outlet of the crosshead 4 and the inlet of the water cooling device 5 should be as small as possible. for example,
When the linear velocity of the optical fiber 2 is 10 to 50 m/min, the above-mentioned interval is desirably about 1 to 50 cm, particularly about 1 to 10 cm.

In Fig. 2, 21 is a step index made of pure silica glass or quartz glass with a burr punt, or a core and cladding layer of a single mode structure, and a quartz glass support provided as necessary. 22 is a silicone layer formed by heat curing or ultraviolet curing after coating, and 23 is a fluorine resin coating layer formed by extrusion molding and quenching.

Examples Example 1 An optical fiber having a thermosetting silicone layer having a thickness of 400 μm on a quartz glass optical fiber having an outer diameter of 125 μm and having a fused silica glass cladding layer was heated at a linear speed of 25 m/min.
The tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer was extruded onto the silicone layer at 400°C, and then the extruded coating layer was rapidly cooled by passing through a water cooling device installed 3 cm from the crosshead outlet. In this way, a resin-coated optical fiber having a tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer layer with a thickness of 700 μm was obtained.

Example 2 The production differed from Example 1 only in that the linear velocity of the optical fiber was 15 m/min and the distance between the crosshead outlet and the water cooling device inlet was 25 cm.

Comparative Example 1 A manufacturing process different from Example 2 was carried out only in that the extruded coating layer was slowly cooled in hot water without using a water cooling device.

The optical fibers manufactured in the above Examples and Comparative Examples all had almost the same initial transmission loss value, but in a heat resistance test where the optical fibers were instantaneously accelerated for 0.75 seconds at 300°C, the transmission loss during the cooling process after heating was The loss increase degree is in Example 1 and Example 2, respectively.
In comparison, Comparative Example 1 had a very large spike phenomenon, which was small at 0.0 dB/Km and 0.28 dB/Km.

Effects The present invention has made it possible to manufacture a resin-coated quartz glass optical fiber with excellent heat resistance. Furthermore, in the manufacturing method of the present invention, since the extrusion coating is rapidly cooled, it is easier to speed up the production line compared to the conventional slow cooling method, and it is possible to manufacture high-performance optical fibers at low cost. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a top view of an example of a production line for implementing the method of the present invention, and FIG. 2 is a cross-sectional structural diagram of an example of a resin-coated silica glass optical fiber manufactured by the method of the present invention. . 1, 6... Bobbin, 2... Silica glass optical fiber coated with a silicone layer, 3... Extruder,
4...Crosshead, 5...Water cooling device, 21...
quartz glass optical fiber, 22... silicone layer, 23... fluorine resin layer.

Claims (1)

[Scope of Claims] 1. A silicone layer is provided on a quartz glass optical fiber having a silica glass cladding layer, a fluorocarbon resin is extrusion coated on top of the silicone layer, and immediately after extrusion, an extrusion coating layer of the fluorocarbon resin is applied. A method for producing a resin-coated quartz glass optical fiber, characterized by rapidly cooling the fiber. 2. The manufacturing method according to claim 1, wherein the fluorocarbon resin is a tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer. 3. The manufacturing method according to claims 1 and 2, wherein the extruded coating layer is rapidly cooled in a water cooling device installed immediately after the extrusion head.