JPS593029A - Manufacture of preform for optical fiber retaining plane of polarization - Google Patents

Abstract

PURPOSE:To manufacture a preform for an optical fiber retaining the plane of polarization with high reproducibility, by making the relative positional relation among four burners arranged around a base material for a preform constant and by providing a uniform temp. difference between flames from the adjacent burners. CONSTITUTION:Four burners 2, 3, 4, 5 are symmetrically arranged around a base material 1 for a preform formed by depositing glass films for a clad and a core on the inner wall of a glass pipe. The burners 2-5 are controlled so that flames from the opposite burners 2, 4 and 3, 5 are kept at the same temp. and that flames from the adjacent burners 2, 3, etc. have a uniform temp. difference. The material 1 is heated with the flames from the burners 2-5 while rotating the burners 2-5 without changing the relative positional relation among the material 1 and the burners 2-5 to obtain a preform for an optical fiber having an elliptical clad or core and retaining the plane of polarization.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a polarization-maintaining optical fiber preform, and particularly to a method for manufacturing a polarization-maintaining optical fiber having an elliptical cladding or core. The present invention relates to a preform manufacturing method.

Using the conventional MCVD method (chemical vapor deposition method), a burner is moved parallel to the preform base material, the preform base material is rotated, and a glass film is attached to the inner wall of a quartz tube to form a cladding and core. In this method, an uneven adhesion layer of glass film is produced in the longitudinal direction of the preform due to uneven rotation.

Therefore, when manufacturing a preform to produce a polarization-maintaining optical fiber that gives anisotropy to the optical fiber by making the cladding core elliptical, the inside of the preform base material, such as a quartz tube, is brought into a reduced pressure state, and the burner is To eliminate hollow parts by heating with a flame and to accurately form an elliptical shape inside the preform, which is the source of forming the cladding or core into an elliptical shape, the preform base material is rotated. It is very difficult to form the elliptical shape with good reproducibility.

An object of the present invention is to provide a method for manufacturing a preform of a polarization-maintaining optical fiber, which eliminates the above-mentioned difficulties and allows the production of a polarization-maintaining optical fiber having a normal elliptical cladding or core with good reproducibility. It's about doing.

In the present invention, a plurality of burners are arranged around the glass tube to which a glass film for forming a cladding and a core is attached to the inner wall of the glass tube, and the glass tube and the second (-) are connected to each other. In a method for manufacturing an optical fiber preform in which the glass tube is heated by the flame of the burner while rotating while maintaining a constant positional relationship, the four burners are arranged at four-fold symmetrical positions, and the four burners are arranged in four-fold symmetrical positions, and The glass tube is heated by controlling the temperature so that the flames of the burners are kept at the same temperature and the flames of adjacent burners have a certain temperature difference.

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 1 is a plan view of an apparatus for carrying out the present invention, and FIGS. 2 to 4 are cross-sectional views showing an example of a polarization-maintaining optical fiber manufactured using a preform manufactured by the apparatus shown in FIG. 2 is a preform base material in which a SiO2-based synthetic glass film containing B2O3 for forming the cladding 10 and a B1O2-based synthetic glass film containing GeO2 for forming the core 9 are attached to the inner wall of a quartz glass tube; ~5 is burner, 6
8 are polarization maintaining optical fibers shown in FIGS. 2 to 4, respectively, 9 is the core thereof, 10 is the cladding, and 11 is the support layer. That is, the preform base material 1 and four burners 2 to 5 are placed around the quartz glass tube of the preform base material 1.
A method of manufacturing an optical fiber preform by heating a SiReform base material 1 with the flames of burners 2 to 5 while rotating the SiReform base material 1 while keeping their relative positional relationship constant, the method comprises: burners 2 to 5 of 4 as shown in Figure 1.
Arranged in rotationally symmetrical positions, the flames of opposing burners 2 and 4 are controlled to the same temperature, and the flames of adjacent burners 6 and 5 are controlled to different temperatures with a certain temperature difference, thereby forming the preform. This is a preform manufacturing method for manufacturing a polarization preserving optical fiber, in which the shuffled 10 or the core 9 is made into an elliptical shape by heating the base material 1, and the front and rear burners 2 and 4 are controlled by a high temperature flame. The direction of the synthetic glass membrane portion on which the cladding 10 or core 9 is to be formed is elliptical so that the direction is the short axis of the ellipse, and the direction of the left and right burners 6.5, which are controlled at a low temperature, is the long axis of the ellipse. A preform of a polarization maintaining optical fiber can be manufactured.

Next, this example will be specifically explained. In this example, at the time of collapse, the temperature of the flame of (-S2, 4) is 1800°C, and the temperature of the flame of (Q-S6,5) is 1700°C.
°C, and the pressure inside the preform base material 1 is approximately -
A preform for a polarization preserving optical core is produced by heating and reducing the pressure in the preform base material 1 to create a viscosity difference in the circumferential direction of the preform base material 1, and from this preform, as shown in FIG. A polarization-maintaining optical fiber 6 having a circular core 9, an elliptical cladding 10, and a circular support layer 11 was obtained.

The one shown in FIG. 6 is similar to the one shown in FIG.
At time D, a synthetic glass film heavily doped with p, Q, etc. is used to form the cladding 10 (second cladding), and the viscosity is higher than that of the core 9 (the first cladding 9' is formed concentrically). By lowering the angle, the polarization-maintaining optical fiber 7 has an elliptical cladding 10.

In addition, in the case shown in FIG. 4, the core 9 is formed into an elliptical shape by using a synthetic glass film highly doped with ()e to form the core 9 during MCVD to lower the viscosity than the cladding 10. A polarization maintaining optical fiber 8 is used.

At the time of collapse in these examples, the pressure inside the preform base material 1 does not necessarily need to be reduced, and solidification can be achieved by applying a temperature gradient to the outer periphery of the preform base material.

As explained above, according to the present invention, the synthetic glass film portion that forms the cladding or core of a polarization-maintaining optical fiber can be manufactured into an elliptical shape that is easily reproducible. This preform can be used to produce a polarization-maintaining optical core injector having a normal elliptical cladding or core with good reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an apparatus implementing an embodiment of the present invention, and FIGS. 2 to 4 show examples of polarization-maintaining optical fibers manufactured using the preform manufactured by the apparatus shown in FIG. FIG. 1 nib form base material, 2 to 5: burner, 6 to 8: polarization maintaining optical fiber, 9: core, 10: cladding, 11:
support layer.

Claims (1)

[Claims] 1. A plurality of burners are arranged around the glass tube to which a glass film for forming a cladding and a core is attached to the inner wall of the glass tube, and the relative positional relationship between the glass tube and the burner is kept constant. In the method for manufacturing an optical fiber preform in which the glass tube is heated by the flame of the burner while being rotated while being maintained, the burner 4
The glass tubes are heated by controlling the temperature so that the flames of the opposing burners are kept at the same temperature and the flames of the adjacent burners have a certain temperature difference. A method for manufacturing a polarization-maintaining optical fiber preform, which comprises heating.