RU2252197C1 - Method of production of a single-mode fiber light-guide maintaining emission polarization - Google Patents

Abstract

FIELD: fiber engineering.

SUBSTANCE: the invention is pertaining to the field of fiber engineering and may be used for production of the optical fiber light-guides maintaining a state of polarization of emission used in physical quantities and fiber communication lines. For production of a single-mode optical fiber light-guide they make long grooves of 3-5 mm deep on an outer surface of a cylindrical billet having a central light-guiding core with a reflecting shell covered with a protective shell formed by a quartz tube. Then they place the indicated billet in a quartz tube, fuse the quartz tube with the indicated billet with formation of longitudinal apertures by the indicated grooves, polish the indicated apertures. Place in the apertures rods made out of the quartz glass alloyed by boron and exercise a drawing of the produced billet with the placed in the indicated apertures boron-silicate rods, during which realize fusion of the boron-silicate rods with the billet.

EFFECT: the invention ensures production of single-mode optical fiber light-guides.

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Description

The invention relates to the field of fiber technology and can be used for the manufacture of optical fibers that maintain a state of polarization of radiation, which can be widely used in physical quantity sensors and fiber communication lines.

The closest known to the proposed one is a method for producing a single-mode fiber waveguide by making grooves on the outer surface of a cylindrical workpiece along it to a depth of 1-2 mm, subsequent fusion of the quartz tube with the workpiece and etching in an etching solution in which the holes inside the workpiece are etched to the required diameter (see RU No. 2043313, C 03 B 37/00, 1995).

The disadvantages of this method are:

- a high probability of melting grooves with a depth of 1-2 mm during the fusion of the workpiece with a quartz tube;

- the occurrence of shells on the surface of quartz glass during the etching of holes in a solution of hydrofluoric acid;

- a high probability of cracking of the workpiece with inserted borosilicate rods during fusion on a thermomechanical machine;

- the presence of an outer layer of silica glass on borosilicate rods, worsening the polarization characteristics of the fiber.

The objective of the invention is to improve the technical characteristics of single-mode optical fibers, preserving the polarization of radiation and reducing the complexity of the manufacturing process of optical fibers.

This task is achieved by the fact that in the method of producing a single-mode optical fiber that preserves the polarization of radiation, including the longitudinal grooves on the outer surface of a cylindrical billet having a central light guide core with a reflective sheath, covered with a protective sheath formed by a quartz tube, the subsequent placement of the specified billet in a quartz tube fusion of a quartz tube with the specified workpiece with the formation of longitudinal holes from the specified grooves, polishing these holes ti, placement of borosilicate rods in said holes and drawing out a fiber from the workpiece with borosilicate rods placed in said holes, these grooves are made to a depth of 3-5 mm, as borosilicate rods use rods made of quartz glass doped with boron without an outer layer of silica glass and in the process of drawing the obtained preform with borosilicate rods placed in the indicated holes, the borosilicate rods are fused with the preform.

Figure 1-5 shows the sequence of technological operations for obtaining round holes in the preform of a single-mode fiber.

Figure 6 shows a cross section of a borosilicate rod, which is usually used in the prototype.

7 shows a cross section of a borosilicate rod, proposed for use.

The patented method is as follows.

In the initial preform for an isotropic single-mode fiber waveguide 1 having a central light guide core 2, with a reflective sheath 3, covered with a protective sheath formed by a quartz tube, longitudinal semicircular grooves 4 are cut from two diametrically opposite sides to a depth of, for example, 4.0 mm. Then the specified workpiece is placed inside the quartz tube 5 and fused with it with the formation of longitudinal holes from these grooves. In the resulting workpiece 6 on a special device, the formed holes are polished 7.

By the described method, holes were prepared in the blanks obtained by the MCVD method. Used preforms 300 mm long, light guide core made of quartz glass doped with germanium, 1.0 mm in diameter, a reflective shell made of quartz glass doped with fluorine and phosphorus, 2.0 mm in diameter, and an outer protective shell formed by a supporting quartz tube, with a diameter 12.0 mm

In the specified workpiece on a grinding machine using a grinding wheel with a semicircular working surface having a radius of curvature of 2.0 mm, grooves are cut from two diametrically opposite sides to a depth of 4.0 mm, after which it is placed inside a quartz pipe having a wall thickness of 5 , 0 mm, and alloyed with it on a thermomechanical machine. After that, on a special device, the process of polishing the formed holes is carried out.

Borosilicate rods are also made by the MCVD method and initially consist of quartz glass 8 doped with, for example, boron, 7.0 mm in diameter and the outer layer of quartz glass 9 with a diameter of 10.0 mm (see Fig. 6). Then, on a special device, the process of grinding the outer layer of quartz glass is performed and, thus, a borosilicate rod 8 with a diameter of 6.0 mm is obtained (see Fig. 7).

After that, borosilicate rods 8 without an outer layer of silica glass with a diameter of 6.0 mm are inserted into the indicated holes 7 of the obtained blank 6 of a single-mode fiber waveguide with a diameter of 6.5 mm.

The specified preform 6 with inserted borosilicate rods 8 is pulled on the installation of the hood in a fiber light guide with simultaneous fusion.

In this way, single-mode fiber optic fibers were fabricated that retained the polarization of radiation with the following characteristics:

- attenuation: α = 3.0 dB / km;

- the length of the polarization beats: L _p = 1.5 mm;

- intermode polarization coupling coefficient: h = (2-5) Z · 10 ^-5 1 / m;

- fiber length: L = 10 km.

Claims (1)

A method of obtaining a single-mode fiber optic fiber preserving radiation polarization, comprising making longitudinal grooves on the outer surface of a cylindrical billet having a central light guide core with a reflective sheath, a protective sheath formed by a quartz tube, subsequent placement of the billet in the quartz tube, fusion of the quartz tube with the specified workpiece with the formation of longitudinal holes from these grooves, the placement of borosilicate rods in these holes and an exhaust for the obtained preform with borosilicate rods placed in the indicated holes, characterized in that said grooves are made to a depth of 3-5 mm, as the borosilicate rods, quartz glass rods doped with boron without an outer layer of silica glass are used, and in the process of drawing the obtained preform with borosilicate rods placed in the indicated holes fuse borosilicate rods with the workpiece.

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