JPH1020123A - Optical attenuator - Google Patents

Abstract

(57) [Problem] To provide an optical attenuator that can be manufactured at a low cost with a simple structure and that can reliably and easily obtain a desired amount of optical attenuation. An optical fiber (2) is provided on a cylindrical core member (23).
2 is wound spirally a plurality of times to attenuate the optical signal passing through the optical fiber 22 by radiation loss, and by adjusting the diameter of the core member 23 and the number of turns of the optical fiber 22, the desired amount of light attenuation is obtained. I tried to get.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical attenuator used for optical communication and the like, and more particularly, to an optical attenuator which has a simple structure, can be manufactured at low cost, and can easily set an amount of attenuation.

[0002]

2. Description of the Related Art Optical attenuators are broadly classified into fixed attenuators having a constant optical attenuation and variable attenuators having an adjustable optical attenuation. Generally, fixed attenuators are repeaters for the purpose of matching optical levels. And the like, and the variable attenuator is used for a measuring instrument for measuring an optical level. In the fixed attenuator, as shown in FIG. 4A, a light attenuating plate 13 that absorbs a part of the optical signal 11 is provided in the optical fiber 12 at an angle, and the light is transmitted through the light attenuating plate 13 to be attenuated. Light attenuation plate 13
Is formed by depositing a metal on a glass substrate, and the amount of light attenuation is determined by the thickness of the metal deposition film.

As shown in FIG. 4B, the variable attenuator is provided with a continuous attenuation plate 16 in which a light attenuation film whose film thickness continuously changes in the circumferential direction is formed by vapor deposition or the like, and a stepwise in the circumferential direction. A step attenuating plate 17 on which a light attenuating film having a variable thickness is formed is rotatably provided facing the step attenuating plate 17. This variable attenuator is provided at an intermediate portion (connecting portion) of the optical fiber cable, and the optical signal 18 passes through both the continuous attenuation plate 16 and the step attenuation plate 17, and the position of the attenuation plates 16, 17 in the rotation direction is changed. Attenuates the optical signal 18 in response to
Rotate 7 to adjust the light attenuation.

[0004]

However, both the fixed attenuator and the variable attenuator described above require attenuating plates 13, 16 and 17 in which a metal is deposited on a glass substrate, so that the manufacturing cost is high. In addition, since the attenuator must be installed in the attenuator, the internal structure of the attenuator is complicated and large. The present invention has been made in view of the above problems, and has as its object to provide an optical attenuator that can be manufactured at low cost and that can have a simplified structure and a reduced size.

[0005]

In order to achieve the above object, an optical attenuator according to the present invention comprises an optical fiber wound around a core member having a diameter corresponding to the optical fiber diameter. In the optical attenuator of the present invention, not only the optical attenuation amount but also the winding length of the optical fiber, the bending curvature of the optical fiber (that is, the diameter of the core member around which the optical fiber is wound), and the number of turns of the optical fiber (the number of turns) ) Etc.
It is desirable to create a table of the relationship between the curvature of the optical fiber, the number of turns, and the amount of light attenuation. Also,
The core member may be made of any material such as metal, resin or rubber, but preferably has a cylindrical or cylindrical shape in order to prevent bending of the optical fiber.

Since the optical attenuator of the present invention is constituted only by winding an optical fiber around a core member, it can be manufactured at a low cost with a simple structure and can be downsized. When manufacturing the optical attenuator, the setting of the optical attenuation can be easily and accurately performed by referring to the above-described table and the like, and the setting of the optical attenuation at the site where the optical fiber cable is laid, that is, the manufacturing is easy. It is.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show an optical attenuator according to an embodiment of the present invention. FIG. 1 is a schematic perspective view, FIG. 2 is a graph showing the relationship between the number of optical fiber turns and the amount of optical attenuation, and FIG. It is a graph which shows the relationship between the diameter of a core member, and light attenuation.

In FIG. 1, reference numeral 20 denotes an optical attenuator. The optical attenuator 20 is formed by winding an optical fiber 22 around a core member 23 a plurality of times in a spiral manner. The core member 23 is formed of a columnar member made of resin or the like. The core member 23 is provided with a hook or the like for attachment to the attenuator housing as necessary, and a fastener for fastening the optical fiber 22 (or a tension member described later).

As the optical fiber 22, a well-known one or a member in which tension members are juxtaposed (a so-called optical fiber cable) is used. Although not explicitly shown in the figure,
As the optical fiber 22, a part of a long optical fiber cable is used, or a connector or a connecting portion for connection is provided at both ends for connection with another optical fiber. The optical fiber 22 is provided with a core member 23.
After being wound around the core member 23, it is fixed to the core member 23 with an adhesive or the like as necessary.

In the optical attenuator 20 according to this embodiment, since the optical fiber 22 is wound around the core member 23 and the optical fiber 22 is bent, an optical signal 21 passing through the optical fiber 22 is provided. (The amount of attenuation is indicated by the thickness of the arrow) is attenuated due to radiation loss. The amount of light attenuation is increased or decreased not only by the length of the optical fiber 22 wound around the core member 23 but also by the number of turns of the optical fiber 22 and the curvature of bending.

That is, when the diameter of the core member 23 is constant at 15 mm (when the curvature of the optical fiber 22 is constant), the light attenuation increases and decreases in proportion to the number of turns as shown in FIG. Further, assuming that the number of windings is constant (five times), as shown in FIG. Therefore, when the optical attenuator 20 is manufactured, a desired amount of optical attenuation can be obtained by referring to the characteristics shown in FIGS.

In particular, this optical attenuator 20
2 is simply wound around the core member 23, so that it can be manufactured at a low cost, and since no special equipment is required for the manufacture, it can be easily manufactured even at the optical fiber cable laying work site.

[0013]

As described above, according to the optical attenuator according to the present invention, the optical fiber is wound around the core member having a diameter corresponding to the optical fiber diameter. It is possible to obtain the effect that the light attenuation can be obtained and the device can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing an optical attenuator according to one embodiment of the present invention.

FIG. 2 is a graph showing characteristics of an optical attenuation amount with respect to the number of turns of the optical attenuator.

FIG. 3 is a graph showing a characteristic of an optical attenuation amount with respect to a diameter of a core member of the optical attenuator.

FIG. 4 is a diagram schematically showing a conventional optical attenuator, wherein a indicates a fixed attenuator and b indicates a variable attenuator.

[Explanation of symbols]

 Reference Signs List 20 optical attenuator 21 optical signal 22 optical fiber 23 core member

Claims (1)

[Claims] 1. An optical attenuator comprising an optical fiber wound around a core member having a diameter corresponding to the optical fiber diameter.