JPS6251213B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an optical fiber, and more particularly to a method of manufacturing an optical fiber having an elliptical core.

In addition to simply using optical fibers as light transmission media, various attempts have been made to utilize changes in the characteristics of optical fibers to use optical fibers themselves as sensors with measurement functions.

By the way, when a single-mode optical fiber that propagates linearly polarized waves is used for optical measurement using optical phenomena such as polarization and phase, the polarization of the linearly polarized waves can be changed due to bending of the optical fiber, vibration of the optical axis, external pressure, etc. This has the disadvantage that the wavefront propagates while rotating within the optical fiber, and the polarization characteristics change, making accurate measurement impossible. Therefore, as an optical fiber whose polarization plane does not rotate due to physical external pressure, etc., and whose polarization characteristics are constant, for example, an elliptical core type constant polarization optical fiber, in which the cross-sectional shape of the core portion is formed in an elliptical shape, is known. For example, it is being put into practical use as a sensor for optically connecting polarized light to an optical waveguide circuit or for measuring large currents using the Faraday effect of light propagating within an optical fiber.

In order to obtain the above-mentioned elliptical core type constant polarization optical fiber, conventionally, for example, a core having a refractive index higher than that of the glass tube is deposited on the inner wall surface of a perfectly circular hollow glass tube, which will become the cladding part, by a common chemical vapor deposition method. After depositing and forming the glass film that will become the part, the glass tube is heated to form a solid material so that the cross-sectional area becomes dense to form an optical fiber base material, and with both sides of the base material ground to a predetermined value, the base material is By heating and drawing the material using an optical fiber drawing device, a small diameter constant polarization optical fiber with only the core portion having an elliptical shape was formed.

However, in the above method, since only the core part is shaped into an ellipse, it is not easy to grind and shape both sides of the optical fiber base material evenly using a grinding device, etc., and the manufacturing process including subsequent surface treatment is difficult. This made the process complicated.

The present invention has been made in view of the above-mentioned conventional points, and its purpose is to eliminate the use of the above-mentioned grinding process,
A preformed optical fiber base material having a core portion and a cladding portion having different refractive indexes is welded to both opposing sides along the longitudinal direction, and the glass member for shaping is sequentially heated from one end to release the light. It is an object of the present invention to provide a new manufacturing method that can easily obtain an elliptical core type polarization-constant optical fiber by integrating a fiber base material and rectifying glass members on both sides and stretching the same.

An embodiment of the manufacturing method according to the present invention will be described in detail below with reference to the drawings.

First, as shown in FIG. 1, an optical fiber base material 3 consisting of a core part 1 and a clad part 2 in the shape of a perfect round solid rod, which are formed in advance by a common chemical vapor deposition method, are placed facing each other on the same diameter. Round rod-shaped shaping glass members 4 made of the same material as the cladding portion 2 of the base material 3 are welded along both sides along the longitudinal direction.
Further, in this embodiment, a complementary shaping glass member 5 made of the same material as the shaping glass member 4 is shown in each R recess 6 on both sides of the base material 3 and the shaping glass member 4 welded along the base material 3. The assembly 7 is made by aligning and welding as shown in FIG. The outer diameter of the base material 3 constituting the aggregate 7, the diameter of the core portion 1, and the outer diameters for shaping and corrective shaping are, for example, 12 mm: 1 mm: 8 mm: 3 mm.

However, the aggregate 7 configured as described above is
As shown in the figure, it is held in a feeding device (not shown), and is sequentially fed into the heating furnace 8 from one end thereof, and the glass members 4 for shaping and shaping of the base material 3 and both side surfaces,
5 is integrally heated and melted and spun at a predetermined spinning speed, as shown in the cross-sectional view of FIG. Part 11 is major axis 10
A desired elliptical core type constant polarization optical fiber 13 formed in an elliptical shape with a width of 5 μm and a minor axis of 5 μm can be easily obtained.

In addition, in the manufacturing process mentioned above, the optical fiber base material 3 and each glass member for shaping and correction shaping 4,
The aggregate 7 composed of 5 may be covered with a glass tube of an appropriate diameter, and while the inside of the tube is depressurized, the tube may be heated and melted and spun as a whole. This eliminates the possibility of air bubbles being contained inside the optical fiber, and furthermore, it becomes possible to obtain an elliptical core type constant polarization optical fiber with good circularity accuracy in the outer diameter.

As is clear from the above description, according to the manufacturing method of the present invention, shaping glass members are welded along the longitudinal direction of both sides of a perfectly circular optical fiber base material formed in advance, and these aggregates are welded. By integrally heating, melting, and spinning, it is possible to easily obtain an elliptical core-type constant polarization optical fiber in which only the core is elliptical and the outer circumference is a perfect circle through a simple process. There are advantages.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view illustrating an embodiment of an assembly consisting of an optical fiber base material and a glass member for shaping in the method for manufacturing an optical fiber according to the present invention, and FIG. 2 is a cross-sectional view for manufacturing an optical fiber according to the present invention. FIG. 3 is a side sectional view showing an embodiment of the method, and FIG. 3 is a cross-sectional view showing an embodiment of an elliptical core type polarization constant optical fiber obtained by the optical fiber manufacturing method according to the present invention. In the figure, 1 is the core part, 2 is the clad part, and 3
is an optical fiber base material, 4 is a cylindrical glass member for shaping, 5 is a cylindrical glass member for compensation shaping, 6 is an R concave portion, 7 is an assembly, 8 is a heating furnace, and 11 is an elliptical core portion of the optical fiber. , 12 is the cladding part of the optical fiber,
Reference numeral 13 indicates an elliptical core type polarization constant optical fiber.

Claims (1)

[Claims] 1. Glass members for shaping are welded to both longitudinally opposing sides of a preformed optical fiber base material having a core portion and a cladding portion having different refractive indexes, and heating is performed from one end of the glass member. 1. A method of manufacturing an optical fiber, which comprises integrating an optical fiber base material and shaping glass members on both sides, and stretching the fiber into an optical fiber having an elliptical core.