JPH03193642A - Method for cooling hermetically coated optical fiber - Google Patents

Abstract

PURPOSE:To efficiently cool a hermetically coated optical fiber before plastic coating by cooling the fiber by direct contact with solid bodies for cooling. CONSTITUTION:An optical fiber 3a is hermetically coated 4 and the hermetically coated optical fiber 3 is brought into direct contact with solid bodies for cooling, e.g. fixed cooling rolls 5, 6 and movable cooling rolls 7A, 7B, 7C before plastic coating 10. When forced cooling is carried out by direct contact with the solid bodies for cooling, unlike the conventional straight drawing path, this travelling path can be made zigzag and the fiber 3 is travelled by an increased length. As a result, air cooling effect is also enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for cooling a hermetically coated optical fiber.

[Prior Art] Compared to transmission methods using electric wires, optical fibers have the characteristics of having a large information transmission capacity and being unaffected by external electromagnetic influences, and are widely used as information media. It is becoming popular in the field. Optical fibers are increasingly utilized, particularly in general communications, computer links and their peripherals.

Incidentally, optical fibers are obtained by vertically inserting an optical fiber base material obtained by CVD or VAD into a heating furnace heated to around 2000° C., melting it, and drawing the material that falls under its own weight.

At this time, since an optical fiber consisting only of a core and a cladding is susceptible to scratches like ordinary glass, it is protected by coating it with plastic resin at the same time as it is drawn. By coating the optical fiber with this plastic resin, the influence of impurities from the outside environment is removed from the optical fiber, and in terms of strength, the plastic resin also serves as a structural support.

By the way, the optical fiber immediately after coming out of the heating furnace has a power of 1600
The plastic resin cannot be coated unless it is cooled down to 80°C or lower. For this cooling technology, natural cooling using air and forced cooling using gas or liquid refrigerants have been proposed and are actually being used.

Currently, hermetic coated optical fibers that are resistant to impurities such as moisture are being developed and manufactured in place of conventional optical fibers. This hermetic coated optical fiber is obtained by covering the surface of the optical fiber with a hermetic coating made of a thin film of carbon or the like immediately after leaving the heating furnace. The hermetic coating protects the glass itself from moisture and other impurities, which are the biggest cause of reduced strength in optical fibers. Furthermore, the hermetic coating hardens immediately after being applied, making it difficult to transmit external stress to the interior.

[Problem to be solved by the invention] Conventional optical fibers have a problem in that solid objects cannot be brought into direct contact with the surface of the optical fiber until it is coated with plastic resin due to stress caused by distortion and adhesion of impurities. was there. For this reason, the natural cooling method requires a long linear drawing process to ensure sufficient cooling, which poses a problem in that the drawing facility becomes oversized. In addition, in the forced cooling method, even when comparing only thermal conductivity,
Since it was not possible to use a solid material that was much larger than a gas or liquid as a refrigerant, there was a problem in that a large amount of gas or liquid had to be consumed to remove the same amount of heat. Furthermore, when attempting to coat an optical fiber in a high temperature state with a resin, the viscosity of the resin decreases due to the temperature of the optical fiber, making it difficult for the resin to adhere to the surface of the fiber, resulting in a problem that uniform and stable coating cannot be achieved.

An object of the present invention is to provide a method for cooling a hermetic coated optical fiber that can be efficiently cooled.

[Means for Solving the Problems] To explain in detail the present invention for achieving the above object, the method for cooling a hermetic coated optical fiber according to the present invention includes applying a hermetic coating to an optical fiber and cooling the hermetically coated optical fiber. After that, the hermetic coated optical fiber is cooled by bringing it into direct contact with a cooling solid before applying the plastic coating.

[Function] Hermetically coated optical fiber has the effect that the influence of moisture and other impurities is much smaller than conventional optical fibers, and it is said that the hermetic coating is applied immediately after leaving the heating furnace and that it hardens quickly. It has characteristics. The present invention focuses on this point, and even if the hermetic coated optical fiber is brought into direct contact with a cooling solid material before being coated with a plastic resin, there is no problem and efficient cooling can be achieved.

In addition, by performing forced cooling by direct contact with a solid material for cooling, it is not only possible to draw the fiber linearly as in the conventional method, but also to bend the running path in multiple stages, so that the running length of the hermetic coated optical fiber can be reduced. increases, and as a result, the cooling effect of air cooling also improves.

[Example] Hereinafter, a specific example of the method for cooling a hermetic coated optical fiber according to the present invention will be described in detail.

FIG. 1 shows an example of a hermetic coated optical fiber manufacturing apparatus for carrying out the method of the present invention. In the figure, 1 is a heating furnace, 2 is an optical fiber base material heated in the heating furnace 1, 3a is an optical fiber drawn from the optical fiber base material 2, and 4 is a hermetic coating on the surface of the optical fiber 3a. 5 and 6 are fixed cooling rolls as cooling solids that directly contact and cool the hermetic coated optical fiber 4, 78 to 7C are fixed cooling rolls 5, 6
The movable cooling rolls 8A to 8C are movable cooling rolls 8A to 8C, which directly contact the hermetic coated optical fiber 3 alternately to cool them, and move the movable cooling rolls 7A to 7C horizontally in opposite directions. 9 is a fiber temperature measuring device for measuring the temperature of the hermetically coated optical fiber 3; 10 is a resin coating device consisting of a resin coating die that coats the surface of the hermetically coated optical fiber 3 with plastic resin; 11 is a cooling roll horizontal movement mechanism; A resin hardener for curing the coated plastic resin, 12 a take-up capstan for taking off the hermetic coated optical fiber 3, 13 a take-up bobbin for taking up the hermetic coat optical fiber 3, 14 a fiber temperature measurement This is a controller consisting of a computer that issues drive commands to the cooling roll horizontal movement mechanisms 8A to 8C in response to commands from the device 9.

Next, a method for manufacturing such a hermetically coated optical fiber 3 and a method for cooling it will be described.

The optical fiber base material 2 is melted in the heating furnace 1, and the obtained optical fiber 3a is drawn from the lower end of the optical fiber 3a.
Immediately after coming out of the container, it is passed through a hermetic coater 4. The hermetic coated optical fiber 3 formed by being coated with carbon or the like in the hermetic coater 4 is first linearly drawn to the fiber temperature measuring device 9. At this time, the hermetic coated optical fiber 3 is brought into contact with the two fixed cooling rolls 5, 6 and several (three in the embodiment) movable cooling rolls 7A to 7C in an alternating manner. Plastic resin is applied to the hermetically coated optical fiber 3 that has passed through the fiber temperature measuring device 9 using a resin coating device 10, and the plastic resin is cured by irradiating ultraviolet rays or thermal energy with a resin curing device 11.

Thereafter, the hermetically coated optical fiber 3 is taken up by a take-up capstan 12 and finally wound onto a take-up bobbin 13.

By the way, the temperature data of the hermetic coated optical fiber 3 measured by the fiber temperature measuring device 9 is taken into the controller 14, and the controller 14 gently drives each of the movable cooling rolls 7A to 7C horizontally until the temperature becomes sufficiently low. Continue to command the cooling roll horizontal movement mechanisms 8A to 8C to do so. As a result, the movable cooling rolls 7A to 7C are gently horizontally moved to the side in contact with the hermetic coated optical fiber 3, respectively. The temperature of the hermetic coated optical fiber 3 is
When the temperature drops to a point where the plastic resin can be applied, the horizontal movement of each of the movable cooling rolls 7A to 7C is stopped.
In this state, the subsequent regular wire drawing process is performed. Thereby, the minimum required cooling length can be obtained according to the linear velocity.

The central axis of each cooling roll 5, 6.7A to 7C is tubular,
A low-temperature liquid is poured into it to cool it down.

In addition, each cooling roll 5. 6. Materials with high heat capacity and thermal conductivity are used for materials 7A to 7C. Generally, materials with large heat capacity have low thermal conductivity. In the present invention, each cooling roll 5. 6. Since a low-temperature liquid flows through the center of 7A to 7C, the heat capacity is relatively small (metals with high thermal conductivity (gold, silver).

It is desirable to use copper, tungsten, iridium, brass, beryllium, magnesium, molybdenum, etc.). In addition, the part that comes into direct contact with the hermetic coated optical fiber 3 has a smooth surface to avoid scratches as much as possible.
Its shape is similar to a reel.

Actually, the drawing speed is 5.0. 7.5. to, 0
(m/5ec) was drawn three times. Figure 2 (A)
(B) 5 cooling rolls 5. 6. A layout diagram of 7A to 7C is shown. At this time, LO is the original cooling length, L is the cooling length after horizontal movement of the movable cooling rolls 7A to 7C, A is the vertical interval between each cooling roll, A=Lo/4, and L1=S+ ・If A L2=82 ・A L3=83-A, then L=[(++7 +FTT3]go)/4] ・L.

becomes. Note that 81 to S3 are dimensionless numbers.

The conditions and results of Examples 1, 2.3 in this case will be shown below.

In addition, FIG. 3 shows Example 1. 2. 3 shows the Weibull distribution for 3.

[Effects of the Invention] As explained above, in the present invention, forced cooling is performed by bringing the hermetic coated optical fiber into direct contact with the solid material for cooling, which has not been done until now, so the solid material for cooling has high thermal conductivity. This has the advantage of making it possible to cool the optical fiber by breaking the high-temperature boundary layer around the optical fiber. Therefore, energy-saving, low-cost, and highly efficient cooling can be achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a hermetic coated optical fiber manufacturing apparatus that implements the method of the present invention, and FIG. 2 (A)
(B) is a layout diagram of five cooling rolls, and FIG. 3 is a Weibull distribution diagram of Examples 1, 2.3. DESCRIPTION OF SYMBOLS 1... Heating furnace, 2... Optical fiber base material, 3... Hermetic coated optical fiber, 3a... Optical fiber, 4
...Hermetic coating device, 5.6...Fixed cooling roll (solid material for cooling), 7A to 7C...Movable cooling roll (solid material for cooling), 8A to 8C...Cooling roll horizontal movement Mechanism, 9... Fiber temperature measuring device, 10...
Resin coater, 11... Resin hardener, 12... Take-up capstan, 13... Winding bobbin, 14... Controller. Diagram (A) (B) Jealousy 1! IIs! I narrow (niq)

Claims (1)

[Claims] After applying a hermetic coating to an optical fiber to make a hermetic-coated optical fiber, before applying a plastic coating,
A method for cooling a hermetically coated optical fiber, the method comprising cooling the hermetically coated optical fiber by bringing the hermetically coated optical fiber into direct contact with a cooling solid.