JPH0772346A - Optical multiplexer / demultiplexer - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to realize a wide bandpass by reducing the difference in wavelength separation between operating wavelengths of a fiber type optical multiplexer / demultiplexer. [Structure] An optical multiplexer / demultiplexer in which an optical fiber 1 and an optical fiber 1 ′ are closely adhered in parallel, and an intermediate portion is fusion-stretched, has a propagation constant of the optical fiber 1 and the optical fiber 1 ′ at the fusion-spreading portion 2. different.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber type optical multiplexer / demultiplexer used for optical communication and optical measurement.

[0002]

2. Description of the Related Art A wavelength demultiplexing degree is a parameter representing the demultiplexing characteristic of an optical multiplexer / demultiplexer. As a typical definition, the ratio of the power of the wavelength intended for transmission and the power of the wavelength not intended for transmission at each emission end is taken, and the smallest value is taken as the wavelength separation degree of the optical multiplexer / demultiplexer.

Conventionally, the same fibers having the same propagation constant are closely adhered in parallel, the intermediate portion is heat-fused and further stretched. However, there is a difference of 2 to 4 decibels or more in the wavelength separation between the operating wavelengths. It was happening. Therefore, it has been difficult to fabricate an optical multiplexer / demultiplexer with high separation and wide bandpass. Among them, as a method of improving only the degree of separation, there has been proposed a method of combining optical multiplexers / demultiplexers in a two-stage cascade or a method of embedding a thin film filter in the middle of the optical multiplexer / demultiplexer by fine processing. , It was not intended to improve the characteristics fundamentally.

In order to solve the above-mentioned problems of the prior art, the present invention makes the wavelength separation at each operating wavelength substantially equal,
It is to provide an optical multiplexer / demultiplexer with high resolution and wide bandpass by averaging and smoothing the waveform of its peak.

[0005]

The optical multiplexer / demultiplexer of the present invention comprises:
In an optical multiplexer / demultiplexer in which at least two optical fibers are arranged in parallel and a fusion splicing portion is formed, the two optical fibers have different propagation constants in the fusion splicing portion. Wave instrument.

[0006]

In the fusion splicing section, the propagation constants of the optical fibers differ from each other, and the difference in the emission characteristics between wavelengths at each operating wavelength is reduced. Therefore, the difference in the wavelength separation degree value at each operating wavelength is reduced. The peak waveform of the wavelength separation becomes gentle, and it becomes possible to manufacture an optical multiplexer / demultiplexer with high separation and wide bandpass.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of an optical multiplexer / demultiplexer according to an embodiment of the present invention.
The same two optical fibers 1 and 1'are fused and stretched at their intermediate portions to form a fused stretched portion 2. In the optical fiber 1 ', the propagation constant of the intermediate portion is changed in advance, and the propagation constants of both fibers 1, 1'in the fusion splicing section 2 are different.

FIG. 2A shows the emission characteristics of the optical multiplexer / demultiplexer according to the present invention shown in FIG. 1. The difference between the loss on the long wavelength side and the loss on the short wavelength side is reduced, and the waveform is also smooth. . For comparison, it is an optical multiplexer / demultiplexer in which two identical optical fibers are fusion-stretched, and there is no difference in the propagation constants of the two optical fibers at the fusion-stretching portion. Show.
As can be seen from FIG. 2B, the emission characteristics of the conventional optical multiplexer / demultiplexer have a smaller loss of emission power on the long wavelength side than those of the present invention shown in FIG. The waveform is also steep.

FIGS. 3A to 3E are first to fifth embodiments showing a method of manufacturing the optical multiplexer / demultiplexer of the present invention. The same figure (a)
Is to press the intermediate portion of the optical fiber 1'in advance to increase the diameter, and to fuse and extend the optical fiber 1 and the enlarged diameter portion. In the same figure (b), the intermediate portion of the optical fiber 1'is pre-stretched to reduce the diameter, and the optical fiber 1 and the diameter-reduced portion are fused and stretched. The figure (c) shows the optical fibers 1, 1'in advance.
The diameter of the intermediate portion is increased, and both fibers are shifted in the longitudinal direction during parallel adhesion so that the clad diameters in the adhesion portion have a difference, and this portion is fusion-stretched. In the same figure (d), the diameter of the middle part of the optical fibers 1 and 1'is reduced in advance,
When closely contacting in parallel, both fibers are shifted in the longitudinal direction so as to have a difference in the clad diameter at the contact portion, and this portion is fused and stretched. In the same figure (e), the middle part of the optical fiber 1 is thinned in advance, the middle part of the optical fiber 1'is thickened in advance, and both fibers are closely contacted in parallel so that the thinned part and the thickened part are closely contacted. The lever portion is fused and stretched.

The manufacturing method of the present invention is shown in FIGS.
In addition to using an optical fiber that has been subjected to a process of increasing or decreasing the diameter of the optical fiber in advance before the fusion or drawing process as described above, the core diameter, the clad diameter, the core refractive index, the clad It is also possible to use an optical fiber in which the parameters peculiar to the optical fiber such as the refractive index are different from the beginning. In addition, the core dopant in the middle part of the optical fiber is thermally diffused by heating to expand the core, or
You may use the optical fiber which doped the dopant in the intermediate part.

Although the above-described embodiment is directed to an optical multiplexer / demultiplexer using two optical fibers, the present invention is not limited to this, and the number of optical fibers may be increased.

[0012]

As described above, according to the present invention, it is possible to easily improve the characteristic difference between the operating wavelengths, which has limited the characteristics of the optical multiplexer / demultiplexer, and to configure a high-performance optical multiplexer / demultiplexer as a single unit. can do.

[Brief description of drawings]

FIG. 1 is a perspective view of an optical multiplexer / demultiplexer showing an embodiment of the present invention.

FIG. 2A is an emission characteristic diagram of the optical multiplexer / demultiplexer of the present invention. (B) is an emission characteristic diagram of a conventional optical multiplexer / demultiplexer.

3 (a) to 3 (e) are first to fifth examples for showing a method of making the propagation constant of an optical fiber different in manufacturing the optical multiplexer / demultiplexer of the present invention. It is a shape figure of a fiber.

[Explanation of symbols]

 1, 1'optical fiber 2 fusion splicing section A, B output port

Claims (1)

[Claims] 1. An optical multiplexer / demultiplexer in which at least two optical fibers are arranged in parallel and a fusion extending portion is formed,
An optical multiplexer / demultiplexer, wherein the two optical fibers have different propagation constants in the fusion splicing portion.