JPH024538B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of a precursor matrix for a single polarizing fiber having asymmetric refractive index grooves.

Conventionally, to manufacture this type of optical fiber base material,
As shown in Fig. 1, a cylindrical base material b having a germanium dove core part a, and a boron dove core part c
Prepare a pair of cylindrical base materials d and d', cut out the cylindrical base material b into a plate with a predetermined thickness so as to include the core part a in the center, and then cut out the cylindrical base material d,
Cut out d′ into a semi-cylindrical shape.

After optically polishing the contact surfaces of the cut-out plate material e and the semi-cylindrical materials f and f', they were inserted into a jacket tube g to serve as a base material.

As described above, the conventional manufacturing method has complicated steps and is expensive because three base materials are required to obtain one base material.

In view of the above-mentioned technical problems, the present invention aims to provide a technique that can manufacture a single polarization optical fiber base material having a desired asymmetric refractive index groove by simply providing a refractive index groove in one glass rod. It is something to do.

In order to achieve the intended purpose, the method for manufacturing a single polarized optical fiber preform having an asymmetric refractive index groove according to the present invention is to produce a glass fiber having a core portion and a cladding portion around the outer periphery of the core portion. Parallel through holes are formed in the cladding part to provide refractive index grooves for imparting birefringence, or blind holes parallel to the core part are formed in the cladding part, and the core part and the cladding part are inserted into the blind holes. It is characterized by filling and solidifying a liquid substance with a lower melting point than that of the refractive index groove for providing birefringence.

Examples of the method of the present invention will be specifically described below with reference to the drawings.

There are two types of refractive index grooves in the present invention: one is a hole provided close to the core, and the other is a hole filled with a predetermined substance.

The former is called a side hole type, and the latter is called a side pit type.

First, to explain how to manufacture the former side hole type, a glass rod 3 consisting of a core part 1 and a cladding part 2 is prepared, and a pair of through holes 4a and 4b extending in the longitudinal direction of the rod 3 are opened. Form a refractive index groove.

The positions of the through holes 4a and 4b are symmetrical to each other with respect to the central axis of the core portion 1, as shown in FIG.

To improve single polarization characteristics, through holes 4a, 4
If the through holes 4a and 4b are formed so as to be in contact with the core part 1, or by extending from the clad part 2 to the core part 1 so as to slightly infringe on the area of the core part 1, good.

Next, the manufacturing method of the latter side pit type will be described. As shown in FIG. 3, a pair of blind holes 5a,
Form 5b.

Next, a liquid substance 7 having a melting point lower than that of the core portion 1 and the cladding portion 2, a volumetric expansion coefficient higher than that of the cladding portion 2, and easily compatible with the material of the cladding portion 2 is injected into the blind holes 5a and 5b.

As the liquid substance 7, metal or multi-component glass is used.

After injection, the liquid substance 7 is solidified to complete the refractive index groove.

Note that in order to fill the blind holes 5a, 5b with a liquid substance, the pulley foam rod 3 is immersed in the liquid substance without injecting it as described above.
may be filled with liquid substance 7.

In both the side hole type and side pit type, a glass drill 6 or the like is used to form the hole.

By drawing the base material thus obtained, a single polarization fiber is obtained.

As described above, in the present invention, the refractive index groove for imparting birefringence is provided on the side surface of the core portion of the glass rod, so manufacturing is simple, and moreover, it is sufficient to prepare one preform rod. , Therefore, it is possible to reduce costs.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional manufacturing method, and FIGS. 2 and 3 are explanatory diagrams of a manufacturing method according to the present invention. DESCRIPTION OF SYMBOLS 1... Core part, 2... Clad part, 3... Glass rod, 4a, 4b... Through hole, 5a, 5b...
...Blind hole, 7...Liquid substance.

Claims (1)

[Claims] 1. In a glass rod comprising a core part and a cladding part around the core part, a through hole parallel to the core part is formed in the cladding part to provide a refractive index groove for imparting birefringence, or a refractive index groove is provided to provide birefringence. It is characterized by forming parallel blind holes in the cladding part, and filling and solidifying the blind holes with a liquid substance having a lower melting point than the core part and the cladding part, thereby providing a refractive index groove for imparting birefringence. A method for manufacturing a single polarization optical fiber preform having an asymmetric refractive index groove.