JPS5992940A - Production of optical fiber having pore - Google Patents

Abstract

PURPOSE:To obtain desired optical fibers without collapsed pores in spinning, by melt spinning a preform under heating while pressurizing the interiors of the pores formed in the long direction of the preform. CONSTITUTION:A glass rod 25 consisting of a core part 23 and clad part 24 is placed in the center of a quartz tube 22, and quartz tubes (26a) and (26b) and quartz rods 27, 27,... are placed on both sides thereof to form a composite, which is then mounted on a glass lathe to heat the outer periphery of the quartz tube 22 with an oxyhydrogen flame while pressurizing the pores (26a) and (26b) with nitrogen. Thus, the gaps in the quartz tube 22 are collapsed to produce a preform 1. A gas (G), e.g. nitrogen, is then fed through a quartz tube 4 into the pores (26a) and (26b) in the preform 1, and the tip part of the preform 1 is charged into a heating furnace 3 while pressurizing the interiors of the pores (26a) and (26b) under a given pressure and melt spun to give the aimed optical fiber 9. Thus, the collapsing of the pores is eliminated in spinning.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an optical fiber having holes (this type of optical fiber includes a polarization constant optical fiber, an image guide fiber, a multi-core optical fiber, etc.).

These are generally used for communication, measurement, or image transmission.

These optical fibers are manufactured by melt spinning a base material having holes, but there is often a problem that the holes are crushed during spinning.

The present invention aims to solve the above problem by pressurizing the inside of the pores during melt spinning. The preform 1 having holes is removed from the base material supplying device 2, and its original part is charged into the heating furnace 3.

A quartz tube 4 is connected to the base end of the preform 10, and
Connect the quartz tube 4 here and the pipe 5 here.

Then, a gas G such as nitrogen is introduced into the pipe 5 to pressurize the inside of the pores of the preform 1.

The degree of pressurization is preferably in the range of 5 to 50+n+nH2O, and the optimum value is determined from the material and dimensions of the preform, the dimensions of the optical fiber to be obtained, the drawing conditions, etc.

In this figure, 6 is a pressure gauge, 7 is a leak valve, and 8 is a pressure gauge.
10 is a wire diameter measuring device for measuring the diameter of the optical fiber 90 after spinning; 10 is a coating device for coating the fiber;
12 is a curing furnace for curing the coated coating layer; 12 is a second wire diameter measuring device for measuring the diameter of the coated optical fiber 9a; 13 is a curing furnace for curing the coated coating layer;
14 is a capstan for taking up the same fiber 9 a ft, and 14 is a drum for winding up the same fiber 9a.

To describe a more specific example, a preform having an outer diameter of 20 mm and having a core 15, a cladding 16, and holes 17 formed therein as shown in FIG. Attach the device and pressurize the inside of the hole 17 with nitrogen at a rate of about 20 m2/min.
? An optical fiber with an outer diameter of 125 mm was taken up at a speed of +, the core of the optical fiber was covered with silicone rubber to make an outer diameter of 350 mm, and the drum 14 was used to wind it up.

The cross-sectional shape of the optical fiber thus obtained was similar to the preform shown in FIG.

As shown in Fig. 3, a preform with a large number of cores 16, 2, etc. [When drawing was performed in the same manner, an optical fiber having a similar shape to the preform was obtained. In Figures 2 and 3, there is only one hole, but
Preforms with two or more holes can also be treated in the same way.

By the way, holes are usually formed by machining the preform (V), but since it is impossible to drill deep holes with this method, the preform is small, and therefore the original fiber is Therefore, in the present invention, a preform in which holes are grown is prepared by machining, and this is drawn using the apparatus shown in FIG.

FIG. 4 shows an example of such a preform, which has a core 18, a clad 19i formed therein, and has holes 20 symmetrical with respect to the core 18i, and a jacket 21 provided around the outer periphery of the clad 19. Here, the clad 19 and the jacket 21 do not necessarily have to be made of different materials, but the core 1
A portion corresponding to a diameter of 5 times or more of the diameter of 8 (if a material with extremely high purity is used in this area, the loss will be reduced).

Further, the refractive index of the core 18, the cladding 19, and the jacket 21 is the highest, and the cladding 19 and the jacket 21 are the same, or the cladding 19 is slightly lower than the jacket 21.

By the way, an optical fiber having Kagaro holes is manufactured by straining as follows.

As shown in FIG. 5, a glass rod 25 consisting of a core portion 23 and a cladding portion 24 is placed in the center of the jacketed quartz tube 22, and furthermore, a glass rod 25 consisting of a core portion 23 and a cladding portion 24 is placed in the center of the jacketed quartz tube 22, and a glass rod 25 is placed on both sides.
26b and the remaining gap [this quartz rod 27.
27... are arranged, and these are circumscribed to the glass rod 25 and inscribed to the inner circumferential wall of the jacketed quartz tube 22.

These materials include GeO2-8i for the core part 231.
The cladding part 24 (5i02 glass) was used, the quartz tubes 26a and 26b were commercially available high-purity synthetic quartz tubes, and the quartz rods 27, 27... were manufactured by the VAD method. The jacketed quartz tube 221 was a commercially available natural quartz tube.

The composite thus assembled is mounted on a glass lathe as shown in FIG. Then, the gap inside the quartz tube 22 is closed.

At this time, the degree of pressurization inside the hole is adjusted by +C so that the hole does not collapse or swell.

The preform produced in this way is manufactured using the apparatus shown in Fig. 1 (
This is attached and wired.

Note that when collapsing the composite shown in Figure 2, the quartz tube 26
A bar made of alumina, carbon, etc. may be inserted into the holes a and 26b, heated and crushed, and then strained to remove the bar.

As described above, in the present invention, since the preform is melt-spun while pressurizing the inside of the pores, the pores are not crushed during spinning.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the device used; Figures 2 and 3 are preforms with holes; J: surface view;
FIG. 4 is a cross-sectional view of a preform obtained by the present invention, FIG. 5 is a composite that is a predecessor of the preform in FIG. 4, and FIG. 6 is an explanatory diagram showing the collabs process of the composite. ...Preform 17.20...Void Figure 1 Figure 2 Cause Figure 3

Claims (1)

[Claims] A method for producing an optical fiber in which a preform in which holes are formed along the longitudinal direction is heated and spun, characterized in that the preform is melt-spun while applying force U inside the holes. Fiber manufacturing method.