JPS6317240A - Coating method for optical fiber and apparatus therefor - Google Patents

Abstract

PURPOSE:To obtain optical fibers coated with a given curing degree at high productivity, by coating an optical fiber with an ultraviolet curing resin condens ing ultraviolet rays on the resin and irradiating the resin with ultraviolet rays while keeping the irradiation quantity at a constant value. CONSTITUTION:The tip of a preform 1 is melted while heating and drawn into an optical fiber 2, which is then coated with an ultraviolet (UV) curing resin 3 using a coating die 4. The optical fiber 8 coated with the UV resin is then cured with ultraviolet ray energy, emitted from an UV lamp 6 and passing through a transparent quartz tube 7. Wire drawing signals detected by a winding bobbin 13 and signals of an ultraviolet ray power meter 14 installed in the transparent quartz tube 7 are processed in an arithmetic proces sor 10 to determine the required travel of the UV lamp 6. A motor 11 is driven according to the travel and the moving UV lamp 6 is moved through a ball screw 12 near the focus. According to this method, the ultraviolet ray energy irradiating the optical fiber can be kept at a constant value even if the wire drawing speed is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical fiber coating method and a coating apparatus, and more specifically, to a method for coating an optical fiber with an ultraviolet curing resin (hereinafter referred to as UV resin). The present invention relates to a method of coating a glass fiber for optical transmission, which has a constant degree of curing and high productivity when the resin is cured by coating and irradiating ultraviolet rays, and a coating apparatus therefor.

Conventional technology Optical fiber coating materials include thermosetting silicone rubber and L
IV resin is used.

FIG. 2(a) is a schematic diagram showing the configuration of a conventional optical fiber coating device.

The illustrated apparatus is provided with a heating furnace 5 that heats and melts the tip of the preform 1. The heated, melted and drawn optical fiber 2 is fed to a coating die 4 containing a UV resin 3. The UV resin-coated optical fiber 8 that has passed through the coating die 4 passes through one focal point of an elliptical reflecting mirror 9. A U-clamp is installed at the other focal point of the reflector.

In order not to complicate the drawing, the elliptical reflecting mirror 9 is shown as a rectangle in FIG. 2(b). The elliptical reflecting mirror 9 generally means a reflecting mirror whose cross section forms part of an oval shape, but in the example shown in FIGS. It is circular and cylindrical, with a mirror surface on the inside.

The UV resin coated optical fiber 8 that has passed through the coating die 4 is
Inside the reflecting mirror 9, it is surrounded by a transparent quartz tube 7, and the U
(2) The ultraviolet rays emitted by the clamp are irradiated onto the UV resin-coated optical fiber 8 via the quartz tube. The UV resin-coated optical fiber whose resin has been cured by irradiation with ultraviolet rays is wound up by the winding bobbin 13.

The optical fiber coating device configured as described above operates as follows.

The tip of the preform 1 is heated and melted in a heating furnace 5, and an optical fiber 2 is drawn. UV resin 3 is applied to the drawn optical fiber 2 using a coating die 4. The UV resin of the UV resin-coated optical fiber 8 is cured by receiving ultraviolet energy from the U-clamp via the transparent quartz tube 7.

2] is a horizontal sectional view of the elliptical reflecting mirror portion of the apparatus shown in FIG. 2(a). As shown in FIG. 2(b), the U-clamp and the UV resin-coated optical fiber 8 are placed at the focal positions of the two elliptical reflectors 90, respectively. Utilizing the fact that the light emitted from one focus of the elliptical reflector is always focused on the other focus, the UV energy emitted by the U-clamp is most efficiently irradiated onto the UV resin-coated optical fiber 8.

Generally, a certain amount of ultraviolet energy is required for LIV resin to cure, so there is a close relationship between the U-clamp output energy used in the production line, that is, the amount of ultraviolet irradiation, and the production line speed. That is, in order to keep the degree of curing of the UV resin constant, it is necessary to keep the U-clamp output energy and linear speed constant. However, within the range until a predetermined linear velocity is reached, UV
Since the degree of curing of the resin also changes, it is not possible to obtain an optical fiber with a constant degree of curing and good transmission characteristics, which causes a decrease in productivity.

Additionally, LIV resins generally react with oxygen during curing, resulting in poor curing. In order to avoid such curing defects, U
The optical fiber coated with V-resin is placed in a transparent quartz tube purged with inert gas and irradiated with ultraviolet rays to harden the UV resin. However, the amount of ultraviolet rays irradiated also changes depending on the material and size of the transparent quartz tube, or the staining of the transparent quartz tube due to volatile components from the UV resin. Therefore, it is difficult to maintain the degree of curing of the UV resin constant even under a constant linear velocity.

Problems to be Solved by the Invention As mentioned above, in the conventional optical fiber coating method, it is difficult to maintain a constant amount of ultraviolet ray irradiation.
As a result, it has been difficult to obtain coated optical fibers with a constant degree of hardening with high productivity.

SUMMARY OF THE INVENTION Therefore, the present invention aims to provide a method and apparatus for coating optical transmission glass fibers with a constant degree of curing and high productivity.

Means for Solving the Problems In order to maintain a constant degree of curing of the UV resin, the inventors investigated various coating methods by controlling the amount of ultraviolet irradiation. We have devised a method for keeping the ultraviolet energy irradiated onto an optical fiber constant by moving it around one focal point of a mirror, depending on the linear velocity and the contamination of the transparent quartz tube, and a device for implementing the method.

That is, the present invention provides a method for coating an optical fiber by applying an ultraviolet curable resin to an optical fiber and curing the resin by irradiating the resin with ultraviolet rays, in which the ultraviolet rays are focused by optical means and the efficiency of the ultraviolet rays is improved. The method is characterized in that the resin is irradiated with ultraviolet rays while changing the amount of ultraviolet rays and keeping the amount of irradiation constant.

Further, according to the present invention, there is provided an optical fiber coating device for irradiating an optical fiber coated with an ultraviolet curable resin with ultraviolet rays to cure the resin, the apparatus comprising: means for emitting ultraviolet rays; a position of the ultraviolet ray emitting means; an elliptical reflector that has a focal point at the position of the traveling path of the optical fiber coated with the resin and focuses the ultraviolet rays emitted from the ultraviolet radiation means and irradiates the resin; An optical fiber coating device is provided, comprising means for changing the condensing efficiency of the ultraviolet rays at a position along the path of the fiber, and curing the resin while maintaining a constant amount of ultraviolet irradiation to the resin. Ru.

In order to change the collection efficiency of the ultraviolet rays, either the ultraviolet radiation means or the elliptical reflector may be moved, or the elliptical reflector may be deformed to change its focal position, or the traveling path of the optical fiber may be changed. This can also be achieved by changing the

According to a preferred embodiment of the present invention, a high light condensing effect can be obtained by using an elliptical reflecting mirror having a cylindrical shape with an oval cross section and a mirrored inner surface.

Function As described above, when coating an optical fiber with an ultraviolet curing resin, the present invention focuses ultraviolet rays using an optical means such as an elliptical reflecting mirror, and changes the efficiency of concentrating the ultraviolet rays onto the resin. The method is characterized in that the resin is irradiated with ultraviolet rays while keeping the irradiation amount constant.

Generally, the amount of ultraviolet irradiation is mainly determined by the U-clamp output energy and the linear speed of the optical fiber. However, in the present invention, for example, an ultraviolet power meter or the like is installed near the traveling path of the optical fiber to measure the irradiation amount, and based on changes in this measured amount, that is, changes in light collection efficiency, the ultraviolet rays emitted by the ultraviolet lamp, etc. The amount of ultraviolet rays irradiated can be kept constant by moving the means or the elliptical reflector, deforming the elliptical reflector, or changing the traveling path of the optical fiber. Therefore, it is possible to coat optical transmission glass fibers with a constant degree of curing of the coating resin with high productivity.

Embodiment FIG. 1(a) shows one of the optical fiber coating apparatuses according to the present invention.
An example configuration is shown.

The illustrated apparatus is provided with a heating furnace 5 that heats and melts the tip of the optical fiber manufacturing preform 1. The heated, melted and drawn optical fiber 2 is fed to a coating die 4 containing a UV resin 3. The U resin-coated optical fiber 8 that has passed through the coating die 4 passes through one of the elliptical reflecting mirrors 9.
passing through two focal points. A U-lamp 6 is installed at the other focal point of the reflecting mirror.

As described above, the elliptical reflecting mirror 9 of this embodiment has a cylindrical shape with an oval cross section and a mirror surface on the inner surface, achieving high light collection efficiency.

Further, the UV resin-coated optical fiber 8 is surrounded by a transparent quartz tube 7 within the reflecting mirror 9, and the ultraviolet rays emitted by the U-clamp are irradiated onto the UV resin-coated optical fiber 8 through the quartz tube. The UV resin-coated optical fiber whose resin has been cured by irradiation with ultraviolet rays is wound up by the winding bobbin 13.

An ultraviolet power meter 14 is installed inside the transparent quartz tube 7, and the output signal of the power make and the drawing speed signal detected by the winding bobbin are connected to the human power of the arithmetic processor 10. . The output of the processor is the motor 11
connected to human power.

The output shaft of the motor has a male thread, and is screwed together with a female thread on the support plate of the U-clamp to form a ball screw 12. Therefore, the rotation of the motor 11 moves the U① clamp.

The optical fiber coating device configured as described above operates as follows.

The tip of the preform 1 is heated and melted in a heating furnace 5, and an optical fiber 2 is drawn. UV fit resin 3 is applied to the drawn optical fiber 2 using a coating die 4. uvvJ
! The oil-coated optical fiber 8 is cured by ultraviolet energy from the UV lamp 6 that passes through the transparent quartz tube 7.

FIG. 1(b) is a horizontal sectional view of the elliptical reflector portion of the apparatus of the invention shown in FIG. 1(a). As shown in Figure 1, etc., the U■ clamp and UVL oil-coated optical fiber 8
are arranged at two focal positions of the elliptical reflecting mirror 9, respectively. U located at one focal point of the elliptical reflector 9
The ultraviolet light emitted by the clamp is located at another focal point, uvI! is focused on a fat-coated optical fiber 8. Therefore,
By moving the U ■ clamp around the focal point,
The light collection efficiency at the position of the V-resin coated optical fiber 8, that is, the amount of ultraviolet ray irradiation can be changed.

Therefore, the drawing speed signal detected at the winding bobbin 13 and the ultraviolet power meter 1 installed in the transparent quartz tube 7 are used.
The signal No. 4 is processed by the arithmetic processor 10 to determine the necessary amount of movement of the U-clamp. According to the determined movement amount, the motor 11 is driven to move the movable LIV lamp 6 around the focal point via the ball screw 12. With this method, the ultraviolet energy irradiated to the optical fiber can be kept constant even when the drawing speed etc. change, and as a result, the UV
It is possible to always maintain a constant degree of curing of the resin.

That is, in the apparatus according to the embodiment of the present invention, the U clamp located at one focal point of the elliptical reflecting mirror 9 is moved in response to changes in the drawing speed and changes in ultraviolet transmittance due to dirt on the quartz tube. . Thereby, the ultraviolet energy irradiated to the UV resin-coated optical fiber 8 located at the other focal point of the elliptical reflecting mirror 9 is kept constant, and the degree of curing of the UV resin is kept constant.

The U-clamp can be moved in any direction by using two or more motors 11 and ball screws 12.

Further, even if the elliptical reflecting mirror 9 is moved or deformed, the same effect as in the case of moving the U-clamp as described above can be obtained.

Furthermore, the same effect can be obtained by installing the U-clamp at one focal point of the elliptical reflecting mirror 9 and moving the UV resin-coated optical fiber 8 from the other focal point.

Next, the optical fiber preform was heated and melted according to the method of the present invention using the apparatus shown in FIG. 1, and an optical fiber having an outer diameter of 125 μm was spun. The drawn optical fiber is coated with UV resin to a thickness of 250 μm, and UV is irradiated with a high-pressure mercury lamp while keeping the amount of UV irradiation constant.
The resin was cured.

FIG. 3 shows the degree of curing of the UV resin with respect to the drawing speed. Here, the horizontal axis shows the drawing speed (m/min), and the vertical axis shows the degree of hardening. As shown in FIG. 3, a constant degree of hardening was obtained over a wide range of drawing speeds from 1 to 300 m/min.

For comparison with the above examples, the UV resin was cured using the prior art apparatus shown in FIG. 2, ie, without controlling the amount of ultraviolet irradiation. Other conditions are the same as in the above example. FIG. 4 shows the degree of curing of the UV resin with respect to the drawing speed in this case. As shown, in order to obtain an appropriate degree of curing of the UV resin, it is necessary to maintain the drawing speed within the range of 300±10 m/min. However, since it is also necessary to control the optical fiber diameter to 125±1 μm, it is extremely difficult to simultaneously control the drawing speed and maintain it within the range of 300±10 m/min.

Effects of the Invention As is clear from the above explanation, according to the optical fiber coating method and apparatus of the present invention, the amount of ultraviolet irradiation can be kept constant depending on the drawing speed, dirt on the quartz tube, etc. Therefore, it is possible to keep the U■ resin hardening degree constant from the initial stage of the wire drawing process, and productivity can be improved. In addition, the signals from the drawing speed detector and the ultraviolet power make are processed to determine the amount of movement of the U lamp, so quick responses and fine adjustments can be made automatically to changes in the amount of ultraviolet irradiation. It is possible to provide a high quality optical transmission glass fiber having a resin coating with a constant degree of hardening.

Therefore, the optical fiber coating method and apparatus according to the present invention can be used in a wide range of applications.

[Brief explanation of the drawing]

FIG. 1(a) is a schematic diagram of one embodiment of the optical fiber coating cover of the present invention, and FIG. 1(b) is a horizontal sectional view of the elliptical reflecting mirror shown in FIG. 1-(a). , and FIG. 2(a) is
FIG. 2 is a schematic diagram of a conventional optical fiber coating device;
Figure (b) is a horizontal cross-sectional view of the elliptical reflector shown in Figure 2 (a), and Figure 3 shows the drawing speed and U in an embodiment of the method of the present invention.
(2) It is a graph showing the relationship between resin hardening resistance. FIG. 4 is a graph showing the drawing speed and U2 (resin hardening resistance) in the method of the prior art. (Main reference numbers) 1. Preform, 4. Coating die, 6.
[JV lamp, 7..Transparent quartz tube, 9..elliptical reflector, 11..
Motor, 13... Winding bobbin, 14... Ultraviolet power meter,

Claims (7)

[Claims] (1) In a method of coating an optical fiber with an ultraviolet curable resin, irradiating the resin with ultraviolet rays, curing the optical fiber, and coating the optical fiber, the ultraviolet rays are focused by optical means and the focusing efficiency of the ultraviolet rays is changed. A method for coating an optical fiber, characterized in that the resin is irradiated with ultraviolet rays while maintaining a constant amount of irradiation of ultraviolet rays. (2) An optical fiber coating device for curing an optical fiber coated with an ultraviolet curing resin by irradiating the resin with ultraviolet rays, comprising means for emitting ultraviolet rays, a position of the ultraviolet ray emitting means, and coating the resin. an elliptical reflector that focuses the ultraviolet rays emitted from the ultraviolet radiation means and irradiates the resin onto the resin; An optical fiber coating device comprising means for changing the collection efficiency of the ultraviolet rays at a position of the traveling path, and curing the resin while maintaining a constant amount of ultraviolet irradiation to the resin. (3) The optical fiber coating device according to claim 2, wherein the light collection efficiency changing means comprises means for moving the ultraviolet radiation means. (4) The optical fiber coating device according to claim 2, wherein the light collection efficiency changing means comprises means for moving the elliptical reflecting mirror. (5) The optical fiber coating device according to claim 2, wherein the light collection efficiency changing means comprises means for deforming the elliptical reflecting mirror. (6) The optical fiber coating device according to claim 2, wherein the light collection efficiency changing means comprises means for changing the traveling path of the optical fiber. (7) The light according to any one of claims 2 to 6, wherein the elliptical reflecting mirror has a cylindrical shape with an elliptical cross section and a mirror surface on the inner surface. Fiber coating equipment.