JPS58135142A - Preparation of single polarized optical fiber - Google Patents

Abstract

PURPOSE:To prepare the titled optical fiber providing core glass with double refraction properties capable of preserving polarized electromagnetic radiation, by covering the circumference of the core with doped silica glass having different coefficients of linear expansion, providing it with anisotropic thermal stress. CONSTITUTION:Glass is deposited on the inside of the rotating quartz tube 11 uniformly in the direction of circle by MCVD process to form the clad layer 12, the rotation of the quartz tube 11 is stopped, the glass layer 14 having a coefficient of linear expansion different from that of core layer glass is deposited on the inside of the clad layer 12 while only one side of the outer periphery of the quartz tube 11 being heated. The quartz tube 11 is rotated by 180 deg., the same glass layer 14 as the above-mentioned layer is deposited on the inside of the clad layer 12 in the suspension state of the rotation. The core layer 13 having higher refractive index than the clad layer 12 is deposited while the quartz tube 11 being rotated. The quartz tube 11 is heated at high temperature, processed to give a dense cross-sectional area, and spun to give single polarized optical fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber-based sensor and a method for manufacturing a polarization-maintaining fiber that enables coherent communication.

In order to preserve the plane of polarization in an optical fiber, it is necessary to vary the physical pressure on the core from the surroundings depending on the direction and to differentiate the propagation speed for orthogonal components due to birefringence strain. Conventionally, by making the core into a column shape,
A method of structurally increasing the propagation constant difference Δβ has been adopted.

In contrast, in the present invention, the periphery of the core is coated with doped silica glass having different coefficients of thermal expansion, and birefringence is imparted by applying anisotropic thermal stress.

The present invention provides a method for manufacturing an optical fiber in which a core glass has birefringence capable of maintaining polarization.

That is, in the present invention, after depositing a glass layer that will become the cladding layer 12 uniformly in the circumferential direction on the inside of the rotating quartz tube 11 (jacket) by the internal CVD method,
The rotation of the quartz tube 110 is stopped, and only the outer periphery of one side of the quartz tube is heated.
4 is deposited on the cladding layer. After this, attach the quartz tube (80
° Glass layer 1 is placed inside the cladding layer while rotating and stopped.
Further, a glass layer to be the core layer 13 is deposited while the quartz tube is rotated. This quartz tube is heated to a high temperature and solidified so that the cross section becomes dense. FIG. 1 shows a cross section of an optical core ingot obtained by further drawing the obtained preform base material.

The outer periphery of the core is covered with a spindle-shaped non-axisymmetric glass layer that has a different coefficient of thermal expansion than the core, so physical pressure in different directions is applied to the core 13, causing birefringence to occur in the core glass. Exception: Diameter 20 φ, length 100 (1 m quartz tube 6 Or
While rotating at a rotation speed of pm, 5iCt4 is applied inside it.
170 cc/min, POCl3 1 5. cc/min 1SF614 cc/min, 02 Gas 10 D D
cc/min and heated to 1050°C (optical pyrometer) using an oxyhydrogen gas moving at 13011IIIZ min to form a cladding layer, then stop the rotation of the quartz tube,
Input raw materials: BiCl2 20 cc/min, BBr3 1
0007 min, POCl35 cc/min, 02 gas 8
00 cc/min, and heated the outer peripheral surface of one side of the quartz tube to 950°C (optical pyrometer) with an oxyhydrogen burner at 5ho2.
-p2o5-B,03 glass was deposited. Thereafter, the quartz tube was rotated 180 degrees, stopped, and then heated to 950° C. to deposit slo, -p 0II-B, 03 glasses.

Furthermore, while rotating the quartz tube at a rotation speed of 60 rpm,
1cz420007 minutes, GeC! t4 6 cc/min,
A core layer was deposited using 800 cc/min of gas as the input material. Furthermore, after stopping the supply of raw material gas,
A preform rod was produced by heating to ~1900°C (optical pyrometer) and solidifying it. This rod was spun into a fiber with an outer diameter of 125 μm in a resistance heating furnace. The polarization characteristics of this fiber were evaluated. The beat length was 2 mm or less, and the polarization plane preservation property was sufficient for practical use.

[Brief explanation of the drawing]

The accompanying drawing is a cross-sectional view showing the structure of a polarized optical fiber obtained by the method of the present invention. Agents 1) Akira Agent Ryo Hagiwara - ノ286- Bi;

Claims (1)

[Claims] After depositing a glass layer that will become the cladding layer inside the rotating quartz tube, the rotation of the quartz tube is stopped and only the outer periphery of one side of the quartz tube is heated to heat the inside of the cladding layer at a different temperature than that of the glass in the core layer. A glass layer with a coefficient of expansion is deposited, and then the quartz tube is rotated by 180 degrees, and while it is stopped, only the outer periphery of the other side is heated to deposit the same glass layer as above in the cladding layer. A method for manufacturing a single polarization optical fiber, comprising depositing a core layer having a higher refractive index than a cladding layer while rotating.