JPH08271738A - Optical fixed attenuator - Google Patents

Abstract

PURPOSE: To provide a highly versatile fixed optical attenuator capable of acquiring stable characteristics by the use of a simple small--sized. CONSTITUTION: The input-side connector having an input-side optical fiber is connected with the output-side connector having an output-side fiber through an adaptor 1. The longitudinal axis line of the sleeve 2 which accepts the tips of the optical fibers of the two connectors in the adaptor 1 is formed staggerly on the input- and output-sides. By this, the core axis of the input-side optical fiber fA is displaced from that of the output-side optical fiber fB to form a fixed optical attenuator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixed optical attenuator used in the field of optical communication and the like, and more particularly to a fixed optical attenuator utilizing loss caused by misalignment of an optical fiber axis. .

[0002]

2. Description of the Related Art For example, in an optical communication system using an optical fiber, it is necessary to attenuate the signal light transmitted in accordance with the optical transmission characteristics of a light receiving section to an optimum level. For example,
In mobile communication in tunnels and underground malls, in order to keep the output of multiple signal oscillators installed in tunnels and underground malls constant, the output of each signal oscillator is adjusted by passing an optical attenuator in the transmission line. I try to keep it constant.

Optical attenuators used to attenuate optical output include:
There are a variable optical attenuator capable of changing the attenuation factor and a fixed optical attenuator having a constant attenuation factor. Although the variable optical attenuator can obtain a desired attenuation factor, it has a drawback that it has a long-term stability and a high cost because it has a mechanism for adjusting the attenuation factor.

On the other hand, the fixed optical attenuator cannot change the attenuation rate, but the structure is simple and the cost is low. Such a fixed optical attenuator has a gap G provided between the input and output optical fibers f _A and f _B (see FIG. 5).
(A)) and one utilizing the axis shift of the input and output optical fibers f _A and f _B (FIG. 5 (B)).

[0005]

The fixed optical attenuator utilizing the gap shown in FIG. 5A has a gap G formed between the optical fibers f _A and f _B (actually opened). JP-A-64-40802), those provided with an optical attenuation medium (JP-A-64-10704 and JP-A-64-24).
No. 304) or one provided with a refractive index matching agent (JP-A-3-25403).

However, in the optical fixed attenuator utilizing such a gap, reflection occurs between the optical fibers f _A and f _B and the gap G to generate noise, or slight attenuation, for example, about 1 dB to 2 dB. There is a drawback in that an optical attenuator having the above attenuation amount cannot be efficiently obtained. Further, the gap is composed of an optical attenuation medium or a refractive index matching agent, the complex work is required to form the gap, manufacturing cost is required,
There are drawbacks such as difficulty in obtaining a desired attenuation rate.

On the other hand, as shown in FIG. 5B, the optical fibers f _A and f _{B for which} the axes are shifted are used as described in, for example, Japanese Patent Laid-Open No. 223603/1988. There is a fixed optical attenuator in which the end faces of f _A and f _B are formed obliquely and pressed against each other in a state where the end faces are abutted against each other to cause axial misalignment. Specifically, a special ferrule is used to cause axial misalignment in the joint portion of the optical fiber within the ferrule, and when a desired attenuation factor is achieved, the ferrule is fixed with an optical adhesive. Therefore, there is a drawback that the ferrule requires special processing and thus becomes expensive.

Therefore, the inventors of the present invention have conducted many research and experiments to solve the problems of the above-mentioned conventional fixed optical attenuator, and as a result, have shown that the optical attenuation is reduced in the adapter for connecting the optical fiber connector. It is convenient to cause this, and in particular, by deforming the shape of the sleeve that is fixed inside the adapter, the optical fiber is misaligned at the joint of the optical fibers, and the desired attenuation factor is obtained. It turns out that it can be obtained with extremely high precision. The present invention is based on the novel findings of the present inventors.

Therefore, an object of the present invention is to provide an optical fixed attenuator which is small in size and has a simple structure and which can obtain stable characteristics.

Another object of the present invention is to have a structure in which optical attenuation is generated in an adapter for connecting an optical fiber connector, and it is possible to cope with various desired attenuations by simply replacing the adapter. The object is to provide an optical fixed attenuator having high property.

[0011]

The above object is achieved by an optical fixed attenuator according to the present invention. In summary, the present invention connects an input-side connector having an input-side optical fiber and an output-side connector having an output-side optical fiber through an adapter, and inputs at an optical fiber connection portion in the adapter. In the fixed optical attenuator in which the core axis of the optical fiber on the side of the optical fiber and the core axis of the optical fiber on the side of the output side are deviated from each other, The optical fixed attenuator is characterized in that the core axis of the optical fiber on the input side and the core axis of the optical fiber on the output side are deviated by shifting them on the output side. The input side and output side connectors are PC type connectors or angled PC type connectors.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical fixed attenuator of the present invention will be described below in more detail with reference to the drawings.

FIG. 3 shows the overall structure of the optical fiber connector 100 (100A, 100B) and the adapter 1 which can realize the optical fixed attenuator of the present invention. In this embodiment, the optical fixed attenuator of the present invention is the adapter 1 which connects the input side connector 100A having the input side optical fiber f _A and the output side connector 100B having the output side optical fiber f _B. , At the optical fiber connection portion in the adapter 1 by shifting the core axis of the input side optical fiber f _{A and} the core axis of the output side optical fiber f _B.

To further explain, referring to FIG. 3, the optical fiber f _A on the input side is attached to the input side connector 100A, and the optical fiber f _B on the output side is attached to the output side connector 100B. (100
A, 100B) are connected via the adapter 1. In this embodiment, the input side connector 100A and the output side connector 1
00B has the same configuration, and a PC type connector or an angled PC type connector is preferably adopted. PC in Figure 3
A mold connector is illustrated. As shown in the figure, the PC-type connector projects outward from the tip end portion of the ferrule 102.
Are arranged, and the optical fibers f _A and f _B are attached to the ferrule 102 via a capillary 104. Since the detailed structure of the PC type connector is well known to those skilled in the art, a detailed description thereof will be omitted.

On the other hand, the adapter 1 has a split sleeve 2 arranged therein, and the split sleeve 2 is held by two holders 4 surrounding the outer circumference thereof.
Further, the two holders 4 are held by two body housings 6 which surround the outer circumference of the holder 4 and are symmetrically arranged. The two main body housings 6 are integrated by fixing the flange portions 8 with screws (not shown). Such a structure of the adapter 1 used together with the PC type connector is also well known to those skilled in the art, and a detailed description thereof will be omitted.

Each end of the adapter 1 is inserted into the corresponding connector 100A, 100B, and the male screw portions 10 at both ends of the adapter 1 are screwed into the female screw portions 106 of the respective connectors 100A, 100B. Both connectors 10
0A and 100B are connected via the adapter 1. As a result, the split sleeve 2 disposed inside the adapter 1
The ferrule 10 of both connectors 100A and 100B.
The tip part of 2 will be fitted. Also, each connector 1
Since the ferrules 102 of 00A and 100B are urged outward by the spring means 108 arranged inside, the distal end surfaces of the ferrules 102 inserted in the adapter 1 contact each other in the split sleeve 2. They come into contact with each other and elastically adhere to each other. At this time, the split sleeve 2 is conventionally formed straight, so that the ferrules 102 are guided by the split sleeve 2 so that the axes thereof coincide with each other, and therefore, the core axis of the optical fiber on the input side and the output side The optical fibers f _A and f _B are connected to each other in a state where the core axis (optical axis) of the optical fiber is matched.

On the other hand, according to the present invention, as shown in FIGS. 1 and 2, the split sleeve 2 in the adapter 1 for receiving the optical fiber tips of both connectors inputs its longitudinal axis. Side and output side, by shifting the core axis O _A of the optical fiber f _A of the input side connector 100A,
Core axis O _B of optical fiber f _B of output side connector 100B
Are formed so as to deviate by an eccentric amount E.

The split sleeve 2 may be manufactured by precision machining so that the longitudinal axis is displaced from the metal plate by the amount of eccentricity E, but the split sleeve 2 in the commercially available adapter 1 is slightly deformed by a tool or the like. It can also be easily produced by (caulking). The eccentricity amount E is variously changed depending on the light attenuation amount.

Also, the optical fibers f _A on the input side and the output side,
It is preferable that both tip portions formed by f _B , the ferrule 102, the capillary 104, and the like are in contact with each other as much as possible so that there is no gap between the both tip portions in order to suppress reflection. For example, as shown in FIG. 1 (A), it may be formed in a spherical shape, or as shown in FIG. 1 (B), it may be formed in an inclined plane shape.

The optical fixed attenuator of the present invention will be described below with reference to embodiments.

Example 1 Single mode quartz optical fiber (core diameter: 10 μm,
Clad diameter: 125 μm) for PC type connector 100A,
It was connected to 100B and this was connected by the adapter 1.
The split sleeve 2 built in the adapter 1 was crimped, that is, deformed in advance by a tool, and its longitudinal axis was shifted on the input side and the output side. At this time, the degree of deformation of the split sleeve 2 was adjusted to produce an optical fixed attenuator having an attenuation amount of 3 dB and 25 dB.

The change with time of the attenuation amount of the optical fixed attenuator thus manufactured was examined. FIG. 4A shows the configuration of the test apparatus at this time. That is, the laser light source 20 (wavelength: 1.3 μm) was connected to the input end of the input side optical fiber f _A , and the optical power meter 30 was connected to the output end of the output side optical fiber f _B.

Further, the reflectance of the optical fixed attenuator was examined by the test apparatus shown in FIG. 4 (B). That is, the optical fiber coupler 40
The laser light source 2 is provided at one input end of (branching ratio 50:50).
0 (wavelength: 1.3 μm), the optical power meter 30 was connected to the other input end, and the optical fixed attenuator 1 was detachably connected to one output end of the optical fiber coupler 40. In such a device, the reflectance was examined by comparing the values when the fixed optical attenuator 1 was connected and when it was not connected.

The test results are shown in Table 1.

[0025]

[Table 1]

As shown above, the amount of attenuation of the optical fixed attenuator is constant and the reflection is suppressed to a low level of -40 dB (below the detection lower limit).

Comparative Example 1 Single-mode quartz optical fiber (core diameter: 10 μm,
Clad diameter: 125 μm) for PC type connector 100A,
The optical fixed attenuator (attenuation amount; 25 dB) was manufactured by connecting to 100B and connecting to the adapter 1. The amount of attenuation was adjusted by providing a space at the tip of the optical fibers f _A and f _B. The reflectance of the optical fixed attenuator thus manufactured was examined in the same manner as in the example. The results are also shown in Table 1.

As described above, the reflection amount of the optical fixed attenuator of Comparative Example 1 is -15 dB, which is larger than that of the optical fixed attenuator of the present invention of Example 1.

In the above embodiment, the split sleeve is caulked to cause axial misalignment, but the split sleeve may be misaligned by etching the split sleeve with an acid, for example, a mixed aqueous solution of sulfuric acid and nitric acid.

[0030]

As described above, in the optical fixed attenuator of the present invention, the longitudinal axis of the sleeve in the adapter for receiving the optical fiber tips of the input side and output side connectors is at the input side and the output side. By shifting, the core axis of the input-side optical fiber and the core axis of the output-side optical fiber are deviated from each other, so that stable characteristics can be obtained with a small and simple structure. In addition, the optical fixed attenuator of the present invention is configured to cause optical attenuation in the adapter for connecting the optical fiber connector, and it is possible to cope with various desired attenuation amounts simply by replacing the adapter. It also has the advantage of high versatility.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view illustrating the configuration of an optical fixed attenuator of the present invention.

FIG. 2 is a perspective view of a sleeve which constitutes the optical fixed attenuator of the present invention.

FIG. 3 is a cross-sectional view illustrating a connection mode of an adapter and both optical fiber connectors that form the optical fixed attenuator of the present invention.

FIG. 4 is a schematic configuration diagram of a performance test apparatus for an optical fixed attenuator of the present invention.

FIG. 5 is a diagram illustrating the principle of a conventional optical fixed attenuator.

[Explanation of symbols]

 1 Adapter Split sleeve 100A, 100B Optical fiber connector 102 Ferrule 104 Capillary

Claims (2)

[Claims] 1. An input-side connector having an input-side optical fiber and an output-side connector having an output-side optical fiber are connected via an adapter, and an input-side optical connector is provided at an optical fiber connection portion in the adapter. In the optical fixed attenuator in which the core axis of the fiber and the core axis of the optical fiber on the output side are deviated from each other, the longitudinal axis of the sleeve in the adapter for receiving the optical fiber tips of the both connectors is set to the input side and the output side. The optical fixed attenuator characterized in that the core axis of the optical fiber on the input side and the core axis of the optical fiber on the output side are deviated by shifting by. 2. The optical fixed attenuator according to claim 1, wherein the input side and output side connectors are PC type connectors or angled PC type connectors.