JPS59232930A - Surface treatment of base material for optical fiber - Google Patents

Abstract

PURPOSE:To collapse easily and economically a base material for an optical fiber by bringing a heat conductive layer on the surface of the base material into contact with a glass etching liq. to dissolve and remove the heat conductive layer. CONSTITUTION:A heat conductive layer 3 is formed on the outside of a quartz glass pipe 2, and a deposited glass layer 4 is formed on the inside of the pipe 2 to obtain a base material 1 for an optical fiber having a hollow 5. The material 1 is rotated, and a glass etching liq. 11 such as a mixed aqueous soln. contg. hydrofluoric acid and a strong acid in a receiving tank 8 is transferred to a shower device 7 with a piping system 10 provided with a pump 9. The liq. 11 is poured on the material 1. The layer 3 on the outside of the material 1 contacts with the liq. 11, and it is dissolved and removed from the outside of the material 1 after the lapse of a fixed time. When the outside diameter of the material 1 after removing the layer 3 is detected with a device for measuring outside diameter in a noncontact state such as a photosensor, the working of the pump 9 is stopped, and the material 1 is washed. The resulting base material 1 is made solid by collapsing at a high temp.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for surface treatment of an optical fiber matrix having a special layer on its outer periphery.

When producing an optical fiber base material, a heat-resistant thermally conductive layer is formed in advance on the external surface of the quartz glass pipe using an external CVD method, and then a heat-resistant, thermally conductive layer is formed on the inner circumferential surface of the glass pipe using an internal CVD method. There are new proposals such as forming a glass deposit layer.

In this proposed example, when the glass pipe is heated from the outside when performing the internal CVD method, the high temperature region in the longitudinal direction of the glass pipe is expanded through the thermally conductive layer.
Moreover, at this time, local overheating of the glass pipe does not occur, and therefore, when forming a glass deposited layer by the internal CVD method (MCVD method), the temperature of the pipe heating source is raised higher than usual, and the raw material gas (gas phase) is By increasing the amount of the glass raw material (glass raw material, vapor phase dope material), the doping speed is improved and the dope material yield is improved by reducing the pipe diameter. Figure 1 shows the optical fiber base material 1 manufactured by the above method. This base material 1
As mentioned above, the quartz-based glass deposited layer 2, the heat conductive layer 3 on the outer circular surface of the pipe, and the glass arc deposited layer 4 on the inner peripheral surface of the pipe
There is a hollow part 6 inevitably left in the pipe axis.

As an example, the thermally conductive layer 3 in the above is 5io2-Ti0
2, and the other side is 5i02 and N, i, Cu
It is also used when interacting with oxides such as XFe and CoXCr. .

On the other hand, the glass deposited layer 4 consists of 5i02-Ge02,
In some cases, other oxides may be contained as dopants.

The above-mentioned optical fiber base material 1, like conventional base materials, must eliminate the hollow part 6 by collapsing at high temperatures. As a result, the collapse temperature must be raised considerably, making the process difficult and moreover, due to the high temperature, a greater amount of thermal energy is consumed than in normal base material processing.

In order to solve the problems of the above-mentioned new proposal, the present invention has created a method for surface treatment of an optical fiber base material provided with a thermally conductive layer, and the specific method will be explained below with reference to the illustrated embodiments.

In FIG. 2, which shows one embodiment of the method of the present invention, the first chuck 6A of a glass lathe (not shown) is shown.

Both ends of the optical fiber base material 1 mentioned above are held between the two ends of the optical fiber base material 1 to rotatably support the base material 1.

Above the optical fiber base material 1 supported in this way, a shower device 7 covering the range of the effective length of the base material is arranged, and below the base material 1, a receiving tank 8 is arranged in correspondence with the shower device A. Shower device 7 and receiving tank 8
and is connected by a piping system 1o having a pump 9.

Furthermore, there is a liquid 11 in the receiving WJs that has a glass corrosive effect.
As the liquid 11, hydrofluoric acid, a mixed aqueous solution of hydrofluoric acid and a strong acid (sulfuric acid, nitric acid, hydrochloric acid, etc.), an ammonium fluoride aqueous solution, silica, or a mixture of two or more of these are appropriately adopted. has been done.

In the embodiment shown in FIG. 2, after the optical fiber base material 1 is brought into a rotating state, the liquid 11 in the receiving WJB is fed to the shower device 7 by the piping system 1° having the pump 9, and from the shower device 7. The liquid 11 is directed toward the optical fiber base material 1.

By doing this, the heat conductive layer 3 on the outer peripheral surface of the optical fiber base material 1 comes into contact with the liquid 11 which has a glass corrosive effect, and after a certain period of time, the heat conductive layer 3 is dissolved by the liquid 11. is removed from the outer periphery of the optical fiber base material 1.

At this time, the outer diameter of the optical fiber base material 1 is measured using a non-contact outer diameter measuring device using an optical sensor, etc. When the outer diameter of the base material is detected, the pump 9 is stopped, and the shower device 7 also stops spraying liquid.

Further, while the pump 9 is operating, the liquid 11 that has fallen from the shower device 7 is collected by the receiver aS and retransmitted to the shower device 7.

After the heat conductive layer 3 has been removed by the etching, the optical fiber base material 1 is then washed with water, alkaline solution, and water, so that the liquid 11 is completely washed away. Thereafter, the base material 1 is subjected to a collapse treatment at high temperature to eliminate the hollow portion 6.

Next, the embodiment shown in FIG. 3 will be explained. In this embodiment, a spray nozzle 12 is used instead of the shower device end in the previous embodiment, and a short receiver tank 13 is used instead of the long receiver s8. Furthermore, in this embodiment, the injection nozzle 12 and the receiving tank 13 are synchronously reciprocated along the longitudinal direction of the optical fiber base material via a traverser (not shown).

In the case of FIG. 3, the liquid 11 is injected into the optical fiber base material 1 through the jet nozzle 12, and the jet nozzle 12 and the receiving tank 13 reciprocate in the longitudinal direction of the optical fiber base material 1 in synchronization with each other. Except for this point, this embodiment is the same as the embodiment shown in FIG.

In addition, when removing the thermally conductive layer 3 from the outer periphery of the optical fiber base material 1 in the method of the present invention, the base material 1 may be immersed in a liquid tank containing a liquid 11 that corrodes glass. When using this immersion method, after the end of the internal encapsulation CVD method (
After the formation of the glass deposited layer 4), heat sealing of both ends of the base material,
Many steps are required before entering the collapse process, such as cooling after heat sealing, etching by dipping, cleaning the base material after etching, attaching support to one end of the base material, unsealing the other end of the base material, attaching support again, and then collapsing. This would require a considerable amount of man-hours.

There is still a possibility that foreign matter may enter the hollow portion 5 of the base material 1 when the end portion of the base material is opened by cutting.

On the other hand, after completing the CVD method for forming the glass deposited layer 4 in FIGS. 2 and 3, the optical fiber base material 1 is mounted on a glass lathe for carrying out the CVD method. , the etching, base material cleaning, and collapse described above can be performed, and not only can the number of man-hours be reduced, but there is no need for intervening problematic steps.

Of course, in the embodiments shown in FIGS. 2 and 3, the liquid 11 will not enter into the hollow portion 6 even if both ends of the base material are not sealed.

Among the embodiments shown in FIGS. 2 and 3, the one shown in FIG. 2 has the advantage of being able to perform high-speed etching, and the one shown in FIG. 3 has the advantage of being easy to treat exhaust gas generated by HF.

As a specific example, an optical fiber base material 1 having an outer diameter of 20.0 mm and a 5 inch 2-Tie 2 heat conductive layer 3 and a thickness of 0.1 mm was surface-treated by the method described in FIG.

The removed liquid 11 was a 23% HF aqueous solution (25°C
) until the outer diameter of the base material reaches 17.95 mm.
It takes 0 minutes.

After the above-mentioned etching was completed, the optical fiber base material 1 was washed with water and then collapsed using a conventional method, resulting in a good collapsed state with no generation of bubbles.

Of course, compared to the base material collapse treatment in which the thermally conductive layer 3 is provided, the above-described specific example is significantly superior in terms of collapse time, collapse time, lower collapse temperature, and thermal energy savings.

As explained above, in the present invention, a thermally conductive layer containing 5i02 is formed on the outer circumferential surface of a quartz-based glass pipe, and a glass deposited layer is formed on the inner circumferential surface of the glass pipe, leaving a hollow portion at the pipe axis. The method for surface treatment of an optical fiber base material in which the thermally conductive layer is formed is characterized by bringing the thermally conductive layer into contact with a liquid that corrodes the glass, and dissolving and removing the thermally conductive layer with the liquid. An optical fiber matrix can be provided that can be easily and economically implemented.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an optical fiber base material before surface treatment according to the method of the present invention, and FIGS. 2 and 3 are explanatory diagrams schematically showing various embodiments of the method of the present invention. 1... Optical fiber base material 2... Glass pipe 3... Thermal conductive layer 4... Glass deposited layer 5... Hollow part 7... Shower device 11... Liquid with glass corrosive action 12...
・Injection nozzle patent applicant agent Makoto Ito, patent attorney

Claims (3)

[Claims] (1) A thermally conductive layer containing Stow is formed on the outer circumferential surface of a quartz-based glass pipe, and a glass deposit layer is formed on the inner circumferential surface of the glass pipe, leaving a hollow portion at the pipe axis. A surface treatment method for an optical fiber base material, which comprises bringing the heat conductive layer into contact with a liquid that corrodes glass, and dissolving and removing the heat conductive layer with the liquid. (2) As a means for bringing the thermally conductive layer into contact with a liquid that corrodes glass, the optical fiber base material is rotated, and the liquid that corrodes glass is directed toward the outer periphery of the optical fiber base material in the rotating state, or A method for surface treatment of an optical fiber base material according to claim 1, which comprises spraying. (3) The liquid that corrodes glass consists of hydrofluoric acid.
1- A method for surface treatment of an optical fiber base material according to claim 1 or 2.