JPS5869734A - Coating method of optical fiber - Google Patents

Abstract

PURPOSE:To obtain an optical fiber having a uniform outside diameter, by adjusting the feed speed of a thermoplastic resin pipe to control the film thickness of a thermoplastic resin to be applied to the thermoplastic resin pipe. CONSTITUTION:A base material 1 is slowly introduced into a fiber drawing furnace 3 by a base material feeding apparatus 2, and heating in the fiber drawing furnace 3 and spun into an optical fiber 5. The outside diameter of the optical fiber 5 is read by an outside diameter measuring apparatus 4, and optical fiber 5 is then passed through a pipe 6 consisting of a thermoplastic resin, which is slowly inserted in a heater 8 by a pipe feeding apparatus 7. In preparing the pipe 6 continuously, the resin extruded through an extruder 13 is passed through a crosshead 14 to form a pipe around the optical fiber 5, and then the pipe 6 is inserted in the heater 8. The pipe 6 is heated locally by the heater 8 and applied to the optical fiber 8. The outside diameter of the coated optical fiber 9 is read by an outside diameter measuring apparatus 10, and the optical fiber 9 is then wound by a winder 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for covering optical fibers, and more particularly to a method for covering optical fibers with a pipe made of thermoplastic resin.

In order to maintain the initial strength of the optical fiber, the conventional method of coating the optical fiber immediately after spinning with plastic is to apply a liquid resin composition to the optical fiber immediately after spinning, and then heat it and irradiate it with ultraviolet light in the next step. Alternatively, a method of solidifying by cooling, etc. was adopted.

However, since this type of coating method uses a liquid resin composition, it is essentially difficult to form a uniform coating around the outer periphery of the fiber. It was located in a different place.

In order to solve this drawback, the present inventors have proposed
As shown in oiqr da 3 (Japanese Unexamined Patent Publication Sho St-//7 Co04I) and Japanese Patent Application Sho 5S-1077417, we proposed a method of heating and softening a thermoplastic resin pipe to coat an optical fiber with thermoplastic resin. did.

However, since the thickness of the optical fiber preform has some nonuniformity in the longitudinal direction, it is necessary to adjust the spinning speed of the optical fiber in order to obtain an optical fiber with a uniform diameter. Such fluctuations in spinning speed are disadvantageous in the pipe coating method; if the pipe is fed at a constant speed, if there is a fluctuation in the spinning speed, the outer diameter of the coated fiber will change accordingly. was there.

In order to solve these drawbacks, the present invention adjusts the pipe feeding speed or pipe manufacturing speed according to the variation in the outer diameter of the coated original fiber. The present invention will be explained in detail below with reference to the drawings.

To carry out the invention,! An apparatus as shown in the ti1 diagram or the 1gλ diagram is used. To operate this, the base material 1 is gradually inserted into the drawing furnace 3 by feeding the base material 1. The base material 1 is heated in the drawing furnace 3 and spun into the optical fiber 5. After the outer diameter is read by an outer diameter measuring device, it is passed through a pipe base made of thermoplastic resin. The heater is gradually inserted into the pipe t by the pipe feeding 7.0 Or, as shown in Fig. 1, in the case of continuous production of vibro, the resin extruded by the extruder 13 is passed through the crosshead/ After a pipe is formed on the outer periphery of the fiber through l, it is inserted into the heater l.
The pipe is locally heated by a heater lti to coat the fiber, and a coated optical fiber is obtained. After the outer diameter of the coated optical fiber 9 is read by an outer diameter measuring device 10, it is wound by a winder @/λ.

In Figure #N1, a feedback circuit //lRj is connected to the outside diameter measuring device 10 and the pipe feeder 70, and in Figure 2, a feedback circuit // is working between the outside diameter measuring device 10 and the extruder 13. The pipe feed speed or pipe production speed is adjusted according to variations in the outer diameter of the coating. In other words, if the read coating outer diameter is larger than the set value, the pipe feed speed or manufacturing speed is slowed down (and if it is smaller than the set value, the pipe feed speed or manufacturing speed is increased to increase the optical fiber The outer diameter of is kept uniform.Examples will be described below.

Example 1 The original fiber base material with an outer diameter of Bwφ was heated and softened to a diameter of about 6121 mm.
The fiber was spun into an optical fiber with an outer diameter of Jj Pa at a speed of 1/min. The optical fiber is passed through a polypropylene pipe with an outer diameter of φ and an inner diameter of 10w5φ.
The original fiber was coated with thermoplastic resin. The coated optical fiber was picked up using an outer diameter measuring device, and the outer diameter of the coated optical fiber was fed back to the pipe feed speed. The pipe feeding speed at this time was 9.1 to 9.7w7 minutes with respect to the setting fJIi9.4Iwx1 minute. In addition, the outer diameter of the coated original fiber is per fiber length/Jw, and the setting f
The results were extremely uniform, with a score of koll~2j2μ compared to IiJjOμ.

Example 2 An optical fiber spun under the same conditions as Example 1 was continuously molded by an extrusion machine to an outer diameter of 10■φ and an inner diameter of j*txφ.
The optical fiber was coated with the thermoplastic resin by passing it through the pipe and heating the pipe to about /90°C.

The outer diameter of the coated original fiber to be coated Ia4 was read using an outer diameter measuring device and fed back to the pipe manufacturing speed. The pipe manufacturing speed at this time is the set value of 37.1w1
J6 for minutes. λ~31.2-1/min. Also, the outer diameter of the coated optical fiber is determined by the length of the fiber/I#m, and the set value CjOμ. It was uniform with 2j2μ Otori.

Comparative Example 1 In Example 1, the outer diameter of the coating was not fed back to the pipe feeding, the pipe feeding speed was kept constant at 9.4 Ivxs 1 minute, and the optical fiber was coated with the thermoplastic resin. The outer diameter of the coated optical fiber at this time is approximately 4IOS-4 for the set value of Pm, per the fiber length of 77m.
1≦lμ■.

As explained above, according to the optical fiber coating method of the present invention, the outer diameter of the optical fiber coated with thermoplastic resin is
Since the feed rate of the pipe or the manufacturing rate of the pipe is fed back, there is an advantage that an optical fiber having an extremely uniform outer diameter can be obtained.

[Brief explanation of drawings]

FIGS. 1 and 2 are configuration diagrams of the apparatus used in the present invention. l...base material, -...base material feed, 3...drawing furnace, g...outer diameter measuring device,! ...Optical fiber, 6...Pipe, 7...Pipe feeding, l...Heater, 9...Coated optical fiber, lθ...Outer diameter measuring device, l/...
Feedback circuit, 12... Volume J [Ii, /3...
・Extruder, /l...Crosshead. Patent applicant: Nippon Telegraph and Telephone Public Corporation Figure 1, Figure 21゛■

Claims (1)

[Claims] L In a method of heating and softening a pipe made of a thermoplastic resin to coat an optical fiber immediately after spinning with the thermoplastic resin, the length of the pipe is adjusted according to the variation in the outer diameter of the coated optical fiber. A method for coating an optical fiber, characterized in that the thickness of the coating is controlled by adjusting the feed speed. 2. In a method in which a pipe made of a thermoplastic resin is manufactured by extrusion molding, the pipe is softened by heating, and the thermoplastic resin is coated on an optical fiber immediately after spinning. A method for coating an optical fiber, characterized in that the thickness of the coating is controlled by adjusting the manufacturing speed of the pipe.