JPH095541A - Production of multicore optical fiber preform - Google Patents

Abstract

PURPOSE: To eliminate the positional deviation of a core, to suppress the generation of bubbles to improve yield and to stabilize the shape of the core to prevent the deformation by bundling and fixing a plurality of a core member using a regular polygonal quartz as a main raw material. CONSTITUTION: The plurality of the core member 2 using the regular polygonal quartz as the main raw material is bundled and fixed. A soot using quartz as a main raw material is deposited on the outer periphery of the core part and heated at a high temp. to vitrify and integrate the core material and the soot under VAD method. Since the core members 2 are regular polygonal and in closely contact with each other in the ridgelines to completely eliminate the gaps between core rods when plural numbers are bundled and fixed, bubbles are not generated there during integrating by heating and then the reduction of yield is prevented. The deformation of the core rod during integrating by heating is prevented and the disadvantage that the core in the resultant preform is deformed to make the cross section non-circular does not occur.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a multicore optical fiber preform, and more particularly to a method for producing a multicore optical fiber preform used in the field of optical communication.

[0002]

2. Description of the Related Art Conventionally, a pumping optical fiber having a core made of glass containing a rare earth element has been used as a component of an optical communication system. In an optical communication system, amplification of an optical signal attenuated by long distance transmission is
A method of once converting an optical signal into an electric signal for electrical amplification and then converting the signal into an optical signal again is implemented. However, in such a method, there is a problem that the relay of large-capacity communication that requires high speed is limited and the system becomes complicated. Recently, the direct optical signal is converted without converting the optical signal into an electric signal. Optical amplifiers capable of amplifying signals are being used.

This optical amplifier has Er, Nd, Pr in the core.
With the addition of a rare earth element such as, the active element is excited by the excitation light incident on the excitation optical fiber,
The stimulated emission directly amplifies the signal light passing therethrough, and in recent years, research on the optical amplifier has become active. As shown in FIG. 4, the main components of the optical amplifier include, in addition to the pumping optical fiber 11, a pumping light source 12 for pumping a rare earth element, a power supply circuit for driving the pumping light source, and a pumping light source. An optical multiplexer 15 for making the pumping light 13 and the signal light 14 incident on the pumping optical fiber 11, an optical isolator 16 for removing the reflected light of the pumping light 13 or the signal light 14,
17, an optical bandpass filter 18 for removing the pumping light contained in the amplified signal light, and the like, which is a pumping optical fiber 11 in which Er is added to the signal light 14 having a wavelength of 1.55 μm band. Of the signal light 14 by propagating the pumping light source 12 having a wavelength of 1.48 μm or 0.98 μm through the optical multiplexer 15 and propagating the pumping light 13 to the pumping optical fiber 11 as well. The signal light 19 is obtained by amplifying the signal light 19 times to about 10,000 times.

In addition, in order to achieve high speed transmission, 1
A wavelength division multiplex transmission system that sends signals of multiple wavelengths into the fiber has been studied, but this is because the optical amplifier used in the wavelength multiplex transmission system is required to have a small amplification wavelength characteristic. In order to reduce the wavelength dependence by adding elements such as Al, P and B to the core, or to insert a filter with wavelength dependence of loss into the amplifier system, the method of correcting the wavelength dependence is examined. Has been done. In addition, a multi-core fiber having a plurality of cores in one fiber is drawing attention because it has a very small band characteristic, and as a method for manufacturing this multi-core fiber, a rare earth element-added core part and a predetermined part are used. A method of making a preform by a jacketing method in which a plurality of core rods having a certain amount of clad portion are put in a jacket tube and heated and combined, and then drawn is used.

[0005]

However, in this jacketing method, when the core rod and the clad tube are heated and combined, the core rod 3 is circular as shown in FIG. 3 (a) in the conventional method. Since this core rod moves in the pipe, there is a disadvantage that the core is displaced in the longitudinal direction, and when multiple core rods are bundled to form a multi-core, a gap is created between the core rods, which causes bubbles. And the yield deteriorates, and further, the core rod and the crack tube are deformed during heating and coalescence, and the core in the finished preform is also deformed, so that the cross section is not circular as shown in FIG. 3 (b). The problem occurs.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a multi-core optical fiber preform which solves the above disadvantages and problems, and it relates to a core member mainly composed of regular polygonal quartz. It is characterized by bundling and fixing a plurality of soot, and depositing a soot containing quartz as a main material on the outer periphery of the core portion by the VAD method, and heating the soot to a high temperature to vitrify the soot and the core material. To do.

That is, the inventors of the present invention have conducted various studies in order to develop a method for manufacturing a multicore optical fiber preform that solves the above-mentioned disadvantages of the conventional method. If it is a square one,
When these multiple cores are bundled and fixed to the multi-core, they are tightly coupled at their ridges and do not exist in the gap between the cores at all. It has been found out that bubbles disappear between the core rods and the yield does not deteriorate. Further, regarding this, if a quartz-based soot is deposited on this multi-core by the VAD method, and this is heated to a high temperature to vitrify the core material and the soot, and these are integrated, they change during this heating and coalescence. The present invention has been completed by confirming that the problem that the core in the completed preform is deformed and the cross section is not circular is eliminated.

[0008]

As described above, in the method for producing a multi-core optical fiber preform according to the present invention, the core member has a regular polygonal shape mainly made of quartz. That is, in the present invention, since the core member 2 has a regular polygonal shape as shown in FIG. 1, when a plurality of these, for example, the seven as shown in FIG. Since there is no gap between the core rods due to the close contact with their ridges, no bubbles are generated here when they are heat-merged, and therefore the yield is not deteriorated.

In the present invention, a silica-based soot made by the flame hydrolysis method of an organic silicon compound such as silicon tetrachloride by the VAD method shown in FIG. 2 is provided on the outer periphery of the core member thus bundled and fixed. After depositing, heating these to high temperature,
This core material and soot are vitrified, and these are integrated to form a multicore optical fiber preform. According to this, the core rod is not deformed during this heating and coalescence, and the finished product is completed. The advantage is given that the core is deformed during reforming and the disadvantage that the cross section is no longer circular does not occur. The method of bundling and fixing the core members may be performed by using a fixing jig made of ceramics.

The core member used here is composed of a core and its surroundings covered with a clad layer having a refractive index lower than that of the core. The core is made of a rare earth element such as Er or N for optical amplification.
d, Pr, etc. or Al may be added, and this is Ge-doped in order to make it have a high refractive index, and this core member is cut into a regular polygonal shape by cutting the outer periphery with a micro grinder or the like. It should be one. The shape of the regular polygon may be a regular triangle, a regular quadrangle, a regular hexagon, or the like, but industrially it is preferable to use a regular hexagon as shown in FIG.

[0011]

Next, examples of the present invention will be described. Example In a synthetic quartz glass, Er as a rare earth element is 400 ppm, A
l was added 10,000ppm, Ge-doped, the outer diameter of a core with a maximum refractive index difference of 1.5% with respect to pure quartz and having an outer diameter of 5mm was covered with a core made of a clad made of synthetic quartz glass and a thickness of 10mmφ. The outer periphery of a certain core member was cut with a micro grinder to form a regular hexagon.

Next, this regular hexagonal core member is attached to 300 mmL.
After bundling these seven to make a multi-core,
This one end is fixed to a fixing jig made of quartz, set in a VAD device, soot having quartz as a main raw material is deposited on the outer periphery of the core member, and the soot is sintered in a sintering furnace to make the soot into a glass. Then, this was integrated with the core member to obtain a multicore optical fiber preform. Therefore, when the optical amplification characteristics of this were examined using the measuring apparatus of FIG. 4, good results were obtained.

[0013]

Industrial Applicability The present invention relates to a method for manufacturing a multi-core optical fiber preform, in which each core rod can be fixed at a predetermined position, so that the position of the core does not shift and the generation of bubbles is suppressed. As a result, the yield is improved, and the shape of the core is stabilized, which provides the advantage that a multicore optical fiber that is not deformed can be obtained.

[Brief description of drawings]

FIG. 1 shows a cross-sectional view of a multicore according to the present invention.

FIG. 2 is a vertical sectional view of a soot generator according to the VAD method used in the present invention.

3A is a cross-sectional view of a multicore optical fiber manufactured by a conventional method, and FIG. 3B is a cross-sectional view of a multicore optical fiber whose core is deformed after jacketing.

FIG. 4 is a vertical cross-sectional view of a main component configuration of a conventionally known optical amplifier.

[Explanation of symbols]

 1 ... Multi-core 2 ... Regular polygonal core member 3 ... Circular core material 4 ... Deformed core material 11 ... Excitation optical fiber 12 ... Excitation light source 13 ... Excitation light 14, 19 ... Signal light 15 ... Optical multiplexer 16, 17 ... Optical Isolator 18 ... Optical bandpass filter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Kamiya 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Co., Ltd. Precision Materials Research Laboratory

Claims (1)

[Claims] 1. A plurality of core members made of quartz having a regular polygonal shape as a main raw material are bundled and fixed, and V is attached to the outer periphery of the core members.
A method for producing a multi-core optical fiber preform, comprising depositing a soot containing quartz as a main material by an AD method, heating the soot at a high temperature, and vitrifying and integrating the core material and the soot.