JPH0336976Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a variable optical attenuator used for various experimental adjustments in the optical path of an optical communication system.

Conventionally, the purpose of variable optical attenuators is to attenuate light, so there are methods such as making the coupling between optical transmission lines coarser and denser, inserting an optical attenuation plate into the optical transmission line, etc.
There are various possibilities, but it is desirable to have an optical attenuator that does not affect its transmission characteristics. Considering these conditions, the latter is more advantageous and is generally adopted.

This type of variable optical attenuator generally uses an ND (Neutral Density) filter as the optical attenuation plate. However, there are two types of ND filters: a light-absorbing type and a light-reflecting type, and the latter is used because it has less wavelength flatness. This reflective ND filter is made by vacuum-depositing metal such as chromium (Cr) on a glass plate, and the schematic configuration of a conventional variable optical attenuator using this ND filter is shown in Figure 1. That is, a
is a side sectional view, and b is a plan view showing a cross section of a main part.
In the figure, 1 is a housing with an operation panel 11 tilted θ, 2 is a rotating shaft rotatably supported by the operation panel 11 and has a light attenuation plate 3 fixed at its tip with a hole bolt 7 and a nut 8; is a knob fixed to the operation panel 11 side of the rotating shaft 2; 5 is incident light; 5' is output light; 6 is a prism.

The operation panel surface 11 of the housing 1 is formed to be inclined at a predetermined angle θ with respect to the incident light 5, and the operation panel 1
1, a light attenuation plate 3 with a metal vapor deposited film 31 such as Cr formed on the glass surface is attached to the rotation axis 2 using a hole bolt 7 and a nut 8 so that the plate surface is perpendicular to and parallel to the rotation axis.
At the same time, a knob 4 is fixed to the operating panel 11 side of the rotating shaft 2, and by rotating the knob 4, the light attenuation plate 3 can be rotated relative to the operating panel 11 to adjust the amount of attenuation. That's what I do. In this state, the incident light 5 enters the light attenuation plate 3, the transmitted light is refracted by the prism 6, and the attenuated output light 5' is emitted. However, when such a variable optical attenuator is incorporated into another optical measuring device or optical device, the attenuation plate 3 is perpendicular to the rotation axis 2, so
If the attenuation amount setting operation surface is inclined by θ degrees with respect to the optical axis 5, the structure of the optical measuring instrument or optical device becomes complicated, and there are problems in that the operability is poor. The surface of the light attenuation plate is inclined with respect to the optical axis, which is necessary to prevent reflected light from returning to the incident optical path, that is, the light source side.

The present invention was developed in view of the above-mentioned problems, and focuses on fixing the light attenuation plate while tilting it at a predetermined angle with respect to the rotation axis. Briefly stated, the present invention is based on an optical attenuation plate that is rotatably supported so that the incident light is transmitted at a predetermined angle other than the angle perpendicular to the plate surface, and the transmitted light is parallel to and parallel to the incident light. In a variable optical attenuator that adjusts the amount of attenuation by rotating the optical attenuation plate so that the directions are opposite to each other, a rotation axis that rotatably supports the attenuation plate is aligned with the direction of the incident light. The optical attenuation plate is parallel to the optical axis and is tilted at a predetermined angle to the rotational axis so as to pivotally support the optical attenuation plate. Embodiments of the variable optical attenuator according to the present invention will be described in detail below with reference to the drawings.

In FIG. 2, a is a side sectional view and b is a plan view showing a main part sectional view for explaining one embodiment of the present invention. In FIG. 2, the variable optical attenuator of this invention is equipped with a housing, a rotating shaft, an optical attenuation plate, a prism, a bolt with a hole, a nut, etc., as in FIG. 1, but the bolt with a hole and the housing are It is characterized by improvements. Therefore, the parts other than the bolts with holes and the casing are given the same reference numerals as in FIG. 1, and the explanation of these parts will be omitted here. The housing 9 that characterizes the present invention is a housing in which the surface of the operation panel 11 is flat and perpendicular to the optical axis;
is a bolt with a hole provided with a hole 101 such that the mounting surface of the light attenuation plate 3 is inclined at a predetermined angle θ with respect to a plane perpendicular to the axis. A lens 12 is provided at the optical input/output portion of the optical fiber to prevent loss of transmitted light by converting the light beam on the optical attenuator side into a parallel light beam.

In this configuration, the operation panel 11 is provided with a light attenuation plate 3, which has a metal vapor-deposited film 31 such as Cr formed on the surface of the glass in a light and dark manner so that the amount of light transmitted changes in a predetermined direction in the rotational direction on the light transmission surface. The light attenuating plate is fixed with a bolt 10 having a shaft hole 101 and a nut 8 so that the mounting surface of the light attenuation plate is inclined at a predetermined angle θ to a plane orthogonal to the plane. Next, the light attenuation plate 3 on which the socket bolt 10 is inserted into the rotation shaft 2 is tilted by θ with respect to the rotation shaft 2, and the rotation shaft 2 is rotatably supported perpendicular to the operation panel 11. I am forced to do it.
That is, the rotation axis 2 is parallel to the optical axis 5 of the incident light.

When the knob 4 is fixed to the operation panel side of the rotation shaft 2 and the knob 4 is rotated, the orthogonal plane of the rotation shaft 2 is θ
The light attenuation plate 3 fixed at an angle of 180° rotates around the rotation axis 2 while changing the angle between the incident light 5 and the output light 5' as shown by the two-dot chain line. According to the results of experiments on the light attenuation plate 3, which rotates while changing a predetermined angle with respect to the optical axis, under the following conditions, the thickness of the light attenuation plate 3 is 1.5 mm, and the inclination angle θ is 2 degrees. In this case, the deviation of the parallel light beam due to the rotation of the optical attenuation plate 3, which depends on the refractive index of the optical attenuation plate, etc., is within 0.1 mm, and the loss variation due to the deviation of the parallel light beam is 0.1 dB or less, which is practical. Results have been obtained that pose no problems. Further, due to the inclination of the light attenuating plate 3, the plate surface does not directly face the incident optical axis 5, so that reflected light does not return to the light source side.

As is clear from the above description, the variable optical attenuator according to the present invention is more effective than the conventional tilted operation panel housing in which the pivot axis of the attenuation plate is non-parallel to the optical axis. As a result, it is easy to implement in each device, has good operability, and can arbitrarily change the angle of inclination of the damping plate with respect to the rotation axis, so it is extremely effective when applied to various optical communication devices.

Note that the present invention is not limited to the above-mentioned embodiments; for example, instead of the casing and the operation panel, it may be used as a supporting member for the stand, and the present invention is not pivoted to the light attenuation plate but is fitted at an angle to a fixed shaft and pivotably pivoted. Needless to say, the prism may also be a simple displacement means such as a combination of reflecting mirrors.

[Brief explanation of the drawing]

Figure 1 shows a conventional variable optical attenuator; a is a side sectional view, b is a plan view showing a cross section of the main part, and
In the figures, a is a side cross-sectional view and b is a plan view showing a cross-section of a main part, for explaining one embodiment of the variable optical attenuator according to the present invention. In the figure, 1 and 9 are the housings, 2 is the rotation axis,
3 is a light attenuation plate, 4 is a knob, 5 is an incident light, 5' is an output light, 6 is a prism, 7 and 10 are bolts with holes, 8 is a nut, 11 is an operation panel, 31 is a metal vapor deposition film, 101 is a Slanted hole, shown.

Claims (1)

[Scope of utility model registration request] Incident light is transmitted through a rotatably supported light attenuation plate at a predetermined angle other than an angle perpendicular to the plate surface, and the transmitted light is parallel to and opposite to the incident light. In the variable optical attenuator, the optical attenuation plate is rotated to adjust the amount of optical attenuation. 1. A variable optical attenuator, characterized in that an optical attenuator plate is pivotally supported in parallel with the rotating shaft and tilted at a predetermined angle.