JPS6216401B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to an optical attenuator used for optical communications, etc.
In particular, the present invention relates to an optical attenuator that is small and inexpensive by disposing a flat plate made of a transparent material between opposing pairs of optical fibers.

(b) Problems with the prior art Conventionally known optical attenuators combine a pair of optical fibers with a collimating lens, and between the collimating lenses, a metal film of varying thickness is deposited in a parallel beam. A method was used in which a glass plate was inserted and the amount of attenuation varied depending on the film thickness. In Fig. 1, a is a schematic block diagram for explaining a conventional optical attenuator, b is a plan view of a metal film-deposited glass disk, 1 and 1' are optical fibers, 2 is a collimating lens, and 3 is a plan view of a metal film-deposited glass disk. 4 is a rotating shaft of the metal film-deposited glass disk.

A collimating lens 2 is provided on each end face of the pair of optical fibers 1 and 1', and a metal film-deposited glass is arranged with a predetermined gap between the collimating lenses 2, and is rotated by a rotating shaft 4 in the gap. Disk 3
are arranged. The metal film-deposited glass disk 3 has a structure in which a metal film of varying thickness is radially vapor-deposited on a circular glass disk, and the outer peripheral edge of the metal film is located in the parallel beam between the collimating lenses. ing. However, the metal film deposited glass disk 3
However, there were problems in that it was difficult to miniaturize due to limitations on metal film deposition, and it was also expensive.

(c) Purpose of the Invention In view of the above-mentioned conventional problems, the present invention provides an optical attenuator in which a transparent material, such as a glass plate, is arranged in the gap between a pair of optical fibers and is inclined with respect to the optical axis. The purpose is to provide

(d) Structure of the Invention In order to achieve the above-mentioned object, the present invention provides a structure in which a pair of optical fibers are disposed on a common optical axis with their end faces facing each other with a predetermined gap, and the pair of optical fibers or This is achieved by arranging a flat plate made of a transparent material between opposing coupling lenses provided on the end face of the fiber, and making the flat plate tiltable with respect to the optical axis.

(e) Embodiments of the invention Examples of the optical attenuator according to the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a schematic configuration diagram for explaining one embodiment of the optical attenuator according to the present invention, in which (a) shows the non-tilted state and (b) shows the tilted state; Parts equivalent to 5 are given the same reference numerals.
is a glass plate, 6 is an optical axis, and 7 is a rotation axis.

A pair of optical fibers 1 and 1' are arranged with a predetermined gap D between them, and a flat plate made of a transparent material, such as a glass plate 5, is disposed in the gap so that the light beam can pass through.The glass plate 5 has an optical axis. The glass plate 5 is supported by a rotating shaft 7 in a direction perpendicular to the optical axis 6, and the glass plate 5 is tilted. However, since the strongest part of the power distribution is incident on the optical fiber, the coupling efficiency between the optical fibers is the highest and is almost the same as when the glass plate 5 is not provided.

In (b), the rotating shaft 7 is rotated to tilt the glass plate 5 with respect to the optical axis 6. When the glass plate 5 is tilted in this way, the light beam moves in parallel, resulting in a weak power distribution. part enters the optical fiber,
The coupling efficiency between the optical fibers becomes low, and the inclination angle can be adjusted to obtain a predetermined amount of attenuation. The variable range of this coupling efficiency can be arbitrarily set by the parameters of the distance between the optical fibers, the thickness of the glass plate 5, the refractive index, the inclination angle, and the fiber NA.

FIG. 3 is a schematic configuration diagram for explaining another embodiment of the optical attenuator according to the present invention. In FIG. 3, optical fiber 1 and optical fiber 1' are coupled by one coupling lens 2, and a glass plate 5 is placed at a position where the light beam from optical fiber 1 is converged by coupling lens 2. It is placed. This embodiment has the advantage that the initial insertion loss can be set low and the amount of attenuation can be easily set large.

In addition, as shown in FIG. 1a, two collimating lenses are used, which are configured to once make a parallel light beam using a collimating lens, and then converge it to one point again using a collimating lens to couple optical fibers 1 and 1'. It is also possible to place a glass plate in a position where the light beams are parallel to each other, but in this case, even if the light beams are moved in parallel, there will be only an extremely small change at the convergence point, and the variable range of attenuation will be limited. Extremely narrow and impractical. Therefore, in the present invention, the glass plate is arranged in a position where the light beams are not parallel, that is, in a radial or convergent position.

(f) Effect of the Invention As is clear from the above description, the optical attenuator according to the present invention is different from the conventional optical attenuator in that the optical attenuator is constructed using a glass plate with a thickness of several mm. The effect is extremely large, as it becomes possible to configure a smaller size and lower cost.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining a conventional optical attenuator.
1 is a schematic configuration diagram, b is a plan view of a metal film-deposited glass disk, FIG. , b shows a tilted state, and FIG. 3 is a schematic configuration diagram for explaining another embodiment of the optical attenuator according to the present invention. In the figure, 1 and 1' are optical fibers, 2 is a collimating lens, 3 is a metal film-deposited glass disk,
4 and 7 are rotation axes, 5 is a glass plate, and 6 is an optical axis, respectively.

Claims (1)

[Claims] 1. Pairs of optical fibers are arranged on a common optical axis so that their end faces face each other with a predetermined gap, and at a position where the light beams between the opposing optical fibers are not parallel, A flat plate made of a transparent material is arranged so as to be tiltable with respect to the optical axis, and by tilting the flat plate, the light beam from one of the optical fibers in the pair is adjusted so that the strongest part of the power distribution is An optical attenuator characterized in that the light beam is shifted from the end face of the other optical fiber and can be incident on the other optical fiber with a predetermined amount of attenuation. 2. The optical attenuator according to claim 1, wherein the flat plate is arranged at a position directly hit by the radial light beam from the one optical fiber. 3. The optical fibers of the pair are coupled by a coupling lens, and the flat plate is disposed at a position where the light beam is converged by the coupling lens. Optical attenuator.