JPS58194752A - Production of preform rod for optical fiber for single-phase polarized light - Google Patents

Abstract

PURPOSE:A glass rod having the core layer and the clad layer is softened by heating for deformation, then the external shape is processed into a round form to produce the titled preform rod of high accuracy in high efficiency. CONSTITUTION:A glass rod 1 consisting of the concentric core layer 2 and clad layer 3 is heated by passing through the heat zone H provided with the furnace 4 for softening, passed through the forming zone provided with rollers 5 to apply external forces to deform the rod into an oval in cross section. Then, a glass layer of the same composition as the clad layer 3 is accumulated on the external surface of the rod by the externally accumulating CVD method into a round rod. The present process gives a preform rod for single-phase polarized light with a desired core shape only by deforming an already made preform rod.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a preform rod for a single polarization optical fiber.

Single-mode transmission type single-polarization optical fiber has the function of transmitting light of only one polarization plane (plane of polarization) among its modes, and this optical fiber is used for sensor applications and coherent It is already known that in order to improve the preservation characteristics of the polarization plane, the birefringence phenomenon within the cross section of the optical fiber is greatly expressed. It has also been proposed that the core be oval, square, or dumbbell shaped.

Of course, such a structural shape is provided from the stage of the preform rod (base material for optical fiber), and by spinning the rod, a single polarization optical fiber having the above-mentioned core shape can be obtained.

Therefore, it is difficult to process a single polarization optical fiber at the preform rod stage.

At present, various types of single-polarized optical cores have been devised. There are almost no technical disclosures on how to easily manufacture this rod, and at present, the glass cutting method, glass deposition method, rod-in-tube method, etc. are appropriately combined, and the processing of the rod is difficult and requires various methods, and the polarization characteristics are difficult to manufacture. Efficiency in manufacturing products is also decreasing.

In view of the above-mentioned problem 5, it is an object of the present invention to provide a new method by which a preform rod for single-polarized optical cores having a desired core shape can be manufactured simply and with high precision. The method will be explained by means of an illustrated example.

The glass rod (1) in FIG.
) and a cladding glass layer (3), and both glass layers +21 +3) have a circular cross section before processing.

In the method of the present invention, the glass rod (1) is passed through the heat zone H and heated as shown in Figure 1, and the four rods (1) softened by the heating are further deformed in the next forming zone F. In the case shown in the figure, a heating furnace (4) such as a carbon resistance furnace or a high frequency furnace is arranged in the heat zone H.
In the molding zone F, rollers such as carbon rollers [51+5
Therefore, in the case of Fig. 1, the glass rod (1) is placed in the heating furnace (4).
), and immediately after that, the roller +
5) Deformed by receiving external force (pressure force) from +5),
As a result, the glass rod (1) becomes as shown in Fig. 2 (0).
When +1, it becomes an ellipse.

Of course, the glass rod deformation fa at this time is Rho 2] 5)
The number of rollers can be arbitrarily determined depending on the shape of the rollers, for example, four rollers (5) as shown in Figure 2 (b) [5]
(5) When +51 is used, a diamond-shaped deformed state is obtained, and in addition, as shown in Fig. 2 (c), the width of the throat roller is small.
When a pair of rollers [5] 151 is used, a dumbbell-shaped deformation is obtained.

The glass rod (1) deformed as described above has a core glass layer (2) and a cladding glass layer (3).
Although the glass rod (1) is deformed, in the next step the glass rod (1)
Process the outer shape into a circle.

In other words, the external C
Glass layer (same composition as cladding (3)) via VD method
The outer shape of the glass rod (1) is made circular (ζ) by depositing glass, or by grinding the cladding (3), or by employing both glass deposition and glass grinding.

In the thus obtained preform rod, the cladding glass layer (3) is circular, while the core glass layer (2) is circular.
maintains the deformed state shown in Figure 2 (B) and (C).

For example, the preform rod (6) obtained from the state shown in Fig. 2 ft) becomes as shown in Fig. 3, and the core gas 5x layer (2
) remains oval.

The above preform rod (6+ Vi) is spun with a quartz-based jacket tube placed over its outer periphery, thereby forming a single polarization optical fiber.

Of course, the single polarization optical fiber thus obtained has a special shape whose core is not a perfect circle, and therefore has single polarization characteristics depending on this.

The heating furnace (4) in the heat zone H may be replaced with an oxyhydrogen burner, and the rollers 15+, +51, . . . to be disposed in the forming zone F may also be replaced with the waste injector 50.

This gas injector is preferably equipped with a flat injection port, and like the roller (5), the injection port is placed around the glass rod (1) and softened by gas injection pressure (external force). All you have to do is deform the four bars (1).

Next, a specific example will be described.

As for the glass rod (1), the composition of the glass layer for the core (2) is Ge 02-8 i 02, and the glass layer for the cladding (3)
The composition of glass layer (2) is 5i02, and the glass layer (2) is glass layer (2).
The outer diameter ratio of 3) is 1:6, and the outer diameter of the glass layer (3) is 301.
11I+, and decided to make the oval type shown in Figure 2 (0). At this time, the heating furnace (4) was a carbon resistance furnace (1800℃).
The two rollers (5) were made of carbon and had a width of 20W.

The moving speed of the glass rod +11 is 20 sa/m1ns for both rollers [5]! 5t + the resulting pressing force is I Kf/i
It is.

The glass rod (1) processed under the above conditions was made of cladding glass In [31 with a long axis and a short axis of 40 t each.
m, 225, the major axis and minor axis of the core glass layer (2) are 6.71111% and 3.71111, respectively, ha!
It was oval in shape.

Thereafter, the glass rod 111 is ground to have an outer diameter of 22 m to form a preform rod (6), and a quartz-based jacket tube is placed on the outer periphery of the preform rod (6), which is then spun to have an outer diameter of 22 m.
A 5 μm single polarization optical fiber was obtained.

This elliptical core single polarization optical fiber showed good polarization preservation.

As explained above, the method of the present invention involves softening a glass rod provided with a core glass layer and a TARRADO glass layer by heating, and applying an external force to the softened glass rod from its outer periphery to deform the four rods. Since the glass rod is characterized in that the outer shape of the glass rod after deformation is processed into a circular shape, the desired preform rod (glass rod) made for ordinary optical fibers can be shaped into the desired F shape by simply using the above-mentioned means. The core shape is obtained, and all that is left to do is to rub the outer shape of the rod in a circular shape by simple external machining.
This is also difficult to implement, and as a whole, preform rods for single-polarized optical fibers can be manufactured with high efficiency and precision.

[Brief explanation of drawings]

Figure 1 is a schematic explanatory diagram showing one embodiment of the method of the present invention, Figures 2 (a), (b), and e) are sectional views showing various modifications of the glass rod, and Figure 3 is a cross-sectional view of the glass rod. Cross-sectional view showing circular processing state (1)...Glass rod (2)...Glass layer for core (3)...Glass layer for cladding (4)e ... Heating furnace (5) ... 0 roller + 61 - Preform rod H 1 ... Heat zone F pot ... Fist / Molding zone Patent applicant's agent Makoto Ifuji No. 1 Figure 2 @ Continued from page 1 0 Author: Kikuchi Isai, Ichihara City, Hata Kaigan-dori 6, Furukawa Densaku Kogyo Co., Ltd., Chiba Electric Wire Works, ゛1

Claims (1)

[Claims] (A glass rod having 11 core glass layers and 2 core glass layers on its outer periphery is softened by heating, and an external force is applied to the softened glass rod from its outer periphery. A preform A for single polarized optical fiber characterized by deforming the glass rod and rounding the outer shape of the glass rod after the deformation.
How to make Rondo. (2) A method for manufacturing a preform rond for a single polarization optical fiber according to claim 1, wherein a roller is brought into contact with the outer periphery of the four bars as means for applying an external force to the glass rods. (3) A method for manufacturing a preform rond for a single polarized optical fiber according to claim 1, wherein gas is blown onto the outer periphery of the four glass rods as means for applying an external force to the glass rods. (4) A single-polarization optical fiber fiber optic according to claim 1, wherein one or both of a glass grinding method and a glass deposition method is employed as a means for processing the outer shape of the glass rod into a circular shape after deformation. Method of manufacturing reform rondo.