JP3449701B2 - Variable optical attenuator and device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable optical attenuator and apparatus for continuously attenuating a parallel beam formed between a pair of optical systems.

[0002]

2. Description of the Related Art In optical communication, a variable optical attenuator that appropriately adjusts the intensity of light is required to ensure transmission quality.

In recent years, wavelength division multiplex communication and parallel multi-channel communication have become widespread. In the wavelength division multiplex communication and parallel multi-channel communication, miniaturization or the like is performed in order to make the light intensity of a plurality of channel signals the same. Attenuation 0.02
A fine adjustment of 0.01 dB is desired.

In this variable optical attenuator, it is proposed to use a filter to attenuate the light and to adjust the shutter diaphragm to attenuate the light.

The former uses plate-shaped filters having different light absorptances to change the amount of light absorption to attenuate transmitted light.

However, in the variable optical attenuator using such a filter, it is difficult to continuously change the attenuation of light, and there is a problem that it is large and insertion loss is large.

On the other hand, in the latter, as seen in Japanese Unexamined Patent Publication No. 54-54651, the amount of light cutoff is continuously changed by closing the shutter to appropriately adjust the light intensity.

A variable optical attenuator using a shutter diaphragm will be described.

FIG. 13 is a plan view of a conventional variable optical attenuator.

As shown in the figure, in the variable optical attenuator, a ferrule 12 is provided at the tip of a pair of optical fibers 11, and a parallel beam 14 region between optical systems 13 provided opposite to the tip side of the ferrule 12 is provided. , A pair of plate-shaped shield plates 1
31, 132 and adjusting means 1 for moving the shielding plates 131, 132 in the plane direction to adjust the shielding amount of the parallel beam 14.
And 40 are provided.

The pair of shield plates 131 and 132 are provided so that their tips are overlapped with each other, and V-shaped notches 131a and 132a are provided at the overlapped tips so as to face each other. The diamond-shaped opening 133 is formed by overlapping the cutouts 131a and 132a of the pair of shield plates 131 and 132, and the size of the diamond-shaped opening 133 is continuously adjusted so that the parallel beam 14 The amount of shielding is being adjusted.

Incidentally, at least the vicinity of the opening 133 of the shielding plates 131 and 132 is subjected to a surface treatment for absorbing the shielded light.

Further, such a pair of shielding plates 131, 1
The size of the opening 133 formed by 32 is adjusted by the adjusting means 140. As the adjusting means 140,
A screw portion 141 that holds one shield plate 131 by being fastened to a flange portion 131b provided on both sides in the width direction of the one shield plate 131 and the apparatus main body 110 is provided. Then, the shield plate 1 is rotated by rotating the screw portion 141.
31 is moved in the surface direction and the size of the opening 133 is changed to adjust the shielding amount of the parallel beam 14.

However, in the variable optical attenuator using the diaphragm of such a shielding plate, when the optical fiber used in the optical system is a single mode fiber, the parallel light of the parallel beam varies depending on the lens diameter. , 0.6-1.
It is 0 mmφ. Therefore, the opening of the shielding plate is 1 mm
Due to the size of the front and rear, it is very difficult to align the opening of the shielding plate with the parallel light of the parallel beam, and there is a problem that the positioning work takes time.

In wavelength division communication, the attenuation is 0.0
Although a small adjustment of 2 to 0.01 dB is required, the size of the opening is 1 in the variable optical attenuator using the diaphragm of the shield plate.
Since there is backlash such as backlash in the screw portion that changes the aperture, there is a large variation in the amount of attenuation. Also, the threaded portion has a pitch of 0.3 to
Since it is formed with 1.0 mm, there is a problem that it is difficult to finely adjust the shielding amount.

In order to solve such a problem, a variable optical attenuator has been proposed which rotates the eccentric cam to move the eccentric cam in a direction substantially orthogonal to the parallel beam, and shields the parallel beam at its outer peripheral surface. ing.

According to such a variable optical attenuator, it is easy to position with respect to the parallel beam, and it is possible to easily perform fine adjustment of the attenuation amount as compared with the variable optical attenuator using the diaphragm of the shielding plate.

[0018]

Here, a variable beam attenuator having such an eccentric cam is used to convert a parallel beam into 45 beams.
FIG. 14 shows the relationship between the displacement of the damping amount and the rotation angle of the eccentric cam when the damping amount is reduced to dB.

As shown in FIG. 14, in the variable optical attenuator using such an eccentric cam, the rotation angle of the eccentric cam is 0 to 7.
There is almost no change in the range of 7 deg, and the relationship of the change in the shield amount of the parallel beam with respect to the rotation of the eccentric cam becomes non-linear. Therefore, in this rotation angle range, the gain of the entire servo system becomes insufficient, and there is a problem that it is difficult to perform positioning control as intended.

Further, in order to change the wide range of 1 to 15 dB of the parallel beam with the attenuation amount of 0.1 dB, in order to control the rotation of the eccentric cam, for example, 1540 Pul.
There is a problem that an encoder having a resolution of se / Rev or higher is required, the number of slits formed on the outer circumference of the encoder is increased, the outer diameter of the encoder is increased, downsizing is difficult, and the cost is high.

In view of such circumstances, it is an object of the present invention to provide a variable optical attenuator and a device capable of finely adjusting the shielding amount, eliminating variations in the shielding amount, and further facilitating positioning.

[0022]

According to a first aspect of the present invention for solving the above-mentioned problems, a parallel beam region is formed between a pair of optical systems facing each other, and the parallel beam is continuously generated. In a variable attenuator for attenuating, the tip of the outer periphery having a substantially cylindrical shape and maximally projecting into the parallel beam is displaced by the rotation of the driving means, and is displaced in a direction orthogonal to the parallel beam to attenuate the parallel beam. At least one of both sides of the parallel beam in the moving direction of the shield member, from a shield variable region that shields the parallel beam by changing the tip position of the shield member to change the attenuation amount. The variable optical attenuator is characterized in that the change of the attenuation amount with respect to the rotation angle of the shielding member is made substantially linear by excluding the end portion.

According to a second aspect of the present invention, in the first aspect, the intensity distribution of the parallel beam with respect to the moving direction of the shielding member is a Gaussian distribution, and the transmitted light amount over the displacement direction of the tip position of the shielding member. If the expressed and ^{2 / e 2 ~-2 /} e 2, variable shielding region for changing the attenuation amount by the displacement of the tip end position of the shield member is substantially 1 / e ² ~ direction of displacement from the reference position The variable optical attenuator is characterized in that it is approximately −1 / e ² .

According to a third aspect of the present invention, in the first aspect, the intensity distribution of the parallel beam with respect to the moving direction of the shielding member is a Gaussian distribution, and the transmitted light amount over the displacement direction of the tip end position of the shielding member. If the expressed and ^{2 / e 2 ~-2 /} e 2, variable shielding region for changing the attenuation amount by the displacement of the tip end position of the shield member is substantially 2 / e ² ~ direction of displacement from the reference position The variable optical attenuator is characterized in that it is approximately −1 / e ² .

According to a fourth aspect of the present invention, in the first aspect, the intensity distribution of the parallel beam with respect to the moving direction of the shield member is a Gaussian distribution, and the amount of transmitted light over the displacement direction of the tip end position of the shield member. If the expressed and ^{2 / e 2 ~-2 /} e 2, variable shielding region for changing the attenuation amount by the displacement of the tip end position of the shield member is substantially 1 / e ² ~ direction of displacement from the reference position The variable optical attenuator is characterized in that it is approximately −2 / e ² .

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the shielding member is a deformed cam in which the radius of the portion that shields the parallel beam gradually increases with rotation. There is a variable optical attenuator characterized in that

A sixth aspect of the present invention is the fifth aspect, wherein the shielding member is approximately 150 degrees to approximately 270 from a reference position.
The variable optical attenuator is characterized in that its tip position moves within the range of the variable shield region by rotating the variable optical attenuator up to a degree.

A seventh aspect of the present invention is characterized in that, in the sixth aspect, the amount of attenuation of the parallel beam changes from approximately 0 dB to approximately 15 dB due to the movement of the range of the variable shield region. Located in the attenuator.

An eighth aspect of the present invention is characterized in that, in the sixth aspect, the attenuation of the parallel beam changes from approximately 0 dB to approximately 45 dB due to the movement of the range of the variable shield region. Located in the attenuator.

A ninth aspect of the present invention is the eccentric cam according to any one of the first to fourth aspects, wherein the shielding member has a perfect circular cylindrical shape and the rotating shaft is eccentric by a predetermined amount. There is a variable optical attenuator.

In a tenth aspect of the present invention based on the ninth aspect, the shield member rotates up to 180 degrees from the reference position so that its tip position moves within the range of the variable shield region and the parallel beam The variable optical attenuator is characterized in that the attenuation amount of is changed from approximately 0 dB to approximately 17 dB.

According to an eleventh aspect of the present invention, in any one of the first to tenth aspects, the drive means is a drive motor, and the drive motor is a pulse motor capable of grasping a rotation angle. Is a variable optical attenuator.

A twelfth aspect of the present invention is the variable optical attenuator according to any one of the first to eleventh aspects, characterized in that the drive means includes a drive motor and a rotation angle grasping means.

According to a thirteenth aspect of the present invention, in the twelfth aspect, the rotation angle grasping means is an encoder provided coaxially with the shielding member and an interrupter for grasping the rotation angle of the encoder. It is a feature of the variable optical attenuator.

A fourteenth aspect of the present invention is the variable optical attenuator according to any one of the first to thirteenth aspects, characterized in that the shielding member is formed of a low thermal expansion material having a small thermal expansion coefficient. It is in.

A fifteenth aspect of the present invention is a variable optical attenuating device including the variable optical attenuator according to any one of the first to fourteenth aspects.

According to the present invention, the parallel beam and the shield member can be easily positioned, and the variable shield region by the shield member is set within a predetermined range, whereby the relationship between the rotation angle of the shield member and the shield amount. Can be approximated to a linear shape, and the fine adjustment of the shielding amount can be performed easily and reliably.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below based on embodiments.

(Embodiment 1) FIG. 1 is a sectional view of a variable optical attenuator having a variable optical attenuator according to Embodiment 1 of the present invention, FIG. 2 is a diagram showing the intensity distribution of a parallel beam, and FIG. FIG. 6 is a plan view of a shielding member.

As shown in FIG. 1, the variable optical attenuator 10 of this embodiment has a pair of optical fibers 11, a ferrule 12 provided at the tip of each optical fiber, and light emitted from the tip of the ferrule 12. Is a parallel beam 14, and a variable attenuator 20 for continuously attenuating the parallel beam 14 formed between the pair of optical systems.

In this embodiment, the pair of optical systems 13 are the ferrules 12 connected to the ends of the pair of optical fibers 11.
The parallel beam 14 is provided on the tip side of the ferrule 12 and radiates light from the tip of one ferrule 12 into a parallel beam 14.
4 is made to converge on the other ferrule 12, and is composed of, for example, an aspherical lens, a Selfoc lens, and the like. In the present embodiment, the light emitted from the optical fiber 11 on the left side in the figure is received by the optical fiber 11 on the right side in the figure via the pair of optical systems 13.

The parallel beam 14 thus formed is
In this embodiment, it is set to 0.6 to 1.0 mmφ.

The intensity distribution of the parallel beam 14 is shown in FIG. As described above, the intensity distribution of the parallel beam 14 can be schematically represented by a Gaussian distribution.

The variable optical attenuator 20 of this embodiment that shields the parallel beam 14 as described above rotates the shield member 30 that shields the parallel beam 14 formed between the optical systems 13 and the shield member 30. Drive means 40.

The shield member 30 has a substantially cylindrical shape and is rotated by the driving means 40 so that the position of the outer peripheral surface is displaced in the direction orthogonal to the parallel beam 14 to change the attenuation amount of the parallel beam 14. In this embodiment, as shown in FIG. 3, the deformed cam has a radius that gradually increases depending on the rotation angle. Further, the shielding member 30 is provided with a cutout portion 32, and by the cutout portion 32,
The shield member 30 faces the parallel beam 14 at a predetermined rotation position so as not to attenuate the parallel beam 14.

Here, FIG. 4 is a schematic plan view showing the shielding state of the parallel beams depending on the rotation angle of the shielding member.

Hereinafter, the intensity distribution of the parallel beam over the displacement direction of the displacement position of the tip 31 which is the portion that projects the maximum into the parallel beam 14 on the outer peripheral surface of the shielding member 30 is represented by a Gaussian distribution as shown in FIG. In case of 2 /
and ^{e 2 ~-2 / e 2} , the tip 3 in the ^{2 / e 2 ~-2 /} e 2
The position of 1 is shown.

As shown in FIG. 4, in the shielding member 30 of the present embodiment, one end of the cutout portion 32 has the tip 3 at the reference position.
1 so that the position is approximately 1 / e ² and the tip 31
Of the variable shielding area that changes the attenuation by the displacement of
e ² to approximately −1 / e ² . In the present embodiment, the tip 31 is rotated from the reference position to 195 deg while displacing the variable shield region from approximately 1 / e ² to approximately −1 / e ² .

More specifically, as shown in FIG. 4A, when the position of the tip 31 is approximately 1 / e ² of the reference position, the shielding member 30 has a range of approximately 2 / e ² to approximately 1 / e ² . Shield. At this time, the rotation angle of the shielding member 30 is set as a reference position and 0 deg.
Then, as shown in FIG. 4 (n), when the shield member 30 attenuates the parallel beam 14 to the maximum, that is, the shield member 30 shields the range of approximately 2 / e ² to approximately −1 / e ² . At this time, the rotation angle is 195 deg.

As described above, the change in the attenuation amount of the parallel beam 14 due to the displacement of the tip 31 of the shielding member 30 is approximately 0 dB.
It becomes 17 dB. It should be noted that within the change range of the attenuation amount, for example, 15 deg in FIG. 4B to 180 in FIG.
When used in the range up to deg, 0.61 dB to 14.
It can be used as a 57 dB variable optical attenuator. Of course, the present invention is not limited to this. For example, 0 deg to 270 d
You may make it use with rotation of eg.

FIG. 5 shows the relationship of the displacement of the attenuation amount of the parallel beam 14 with respect to the rotation angle of the shielding member 30.

As shown in the figure, the attenuation amount of the parallel beam 14 with respect to the rotation angle of the shielding member 30 is almost linear, and the attenuation amount increases in proportion to the increase of the rotation angle. for that reason,
It is possible to easily control the attenuation amount of the parallel beam, that is, the rotation angle of the shielding member 30, and easily and surely perform the fine adjustment of the attenuation amount.

The material of the shielding member 30 is
The material is not particularly limited and, for example, metal or plastic can be used, but when the parallel beam 14 is shielded, the shielding member 3 is used.
There is a possibility that an error may occur in the attenuation amount of the parallel beam 14 due to the thermal expansion of 0. Therefore, it is preferable to use a low thermal expansion material having a small thermal expansion coefficient. Even if the outer peripheral surface of the shielding member 30 that shields the parallel beam 14 is mirror-finished, the outer peripheral surface is a curved surface, so that the shielded light does not reflect toward the light source, and the finished state of the outer peripheral surface is not particularly limited. .

The thickness of the shield member 30 is not particularly limited as long as it is larger than the diameter of the parallel beam 14, that is, 1 mm in the present embodiment, but the shield member 30 can be easily positioned with respect to the parallel beam 14 and processed. Is preferably 3 mm or more.

Further, in the shape of the shielding member 30 as described above, the values shown in the following Table 1 are calculated by back calculation so that the relationship of the displacement of the attenuation amount with respect to the rotation angle becomes substantially linear,
Can be formed.

[0056]

[Table 1] Angle (deg) Radius (mm) X coordinate (mm) Y coordinate (mm) 02.002.000.00102.152.
110.370202.202.070.75302.2
41.941.12402.271.741.4650
2.301.481.76602.32.1.162.0
1702.340.802.20802.360.41
2.32902.380.002.381002.39
-0.422.3611102.41-0.822.26
1202.42-1.212.101302.44-
1.571.871402.45-1.871.571
502.46-2.131.231602.47-2.
320.851702.48-2.450.43180
2.49-2.490.00 On the other hand, the drive unit is not particularly limited as long as the rotation angle can be grasped, and in the present embodiment, for example, has a drive motor 41, an encoder 42, and an interrupter 43.

As the drive motor 41, an ultrasonic motor is used in this embodiment, and the rotary shaft 41a of the drive motor 41 is used.
The encoder 42 and the shielding member are held by the.

The encoder 42 measures the rotation angle of the drive motor 41, that is, the rotation angle of the shielding member. For more information,
The encoder 42 is held by the rotary shaft 41a of the drive motor 41 at the same time as the shield member 30, detects a slit (not shown) provided in the encoder 42 by an interrupter 43 fixed to the variable optical attenuator 10, and detects the number of detected slits. The minute rotation angle is measured by counting. By measuring the rotation angle of the encoder 42, the rotation angle of the shielding member 30 is grasped, and the drive motor 41
The amount by which the shield member 30 shields the parallel beam 14 is controlled by controlling the rotation angle of the beam.

In this embodiment, the attenuation amount is 0.61.
At the time of dB, the rotation angle of the shielding member 30 is 15 deg, 16.
Since it is 195 deg at 43 dB, rotation of about 1.138 deg / step is required when decomposing the attenuation range of 0.61 to 16.43 dB in steps of 0.1 dB. Therefore, the encoder has 316Puls
A slit of e / Rev or more is required.

Further, the drive means 40 of this embodiment is composed of the drive motor 41, the encoder 42 and the interrupter 43, but it is not limited to this as long as the shielding member 30 can be rotated and the rotation angle can be grasped. Alternatively, a pulse motor may be used as the drive motor so that the drive motor itself can grasp the rotation angle.

The variable optical attenuator 20 of this embodiment as described above.
For the positioning of the parallel beam 14 with respect to the parallel beam 14, the shield member 30 is rotated by the driving means 40 to shield the parallel beam 14 and the attenuation amount of the parallel beam 14 is measured. Is fixed at a position of 16.43 dB for positioning. By positioning the variable optical attenuator 20 in this manner, the shield member 30 can be positioned easily and reliably with respect to the parallel beam 14.

(Second Embodiment) FIG. 6 is a plan view of a variable optical attenuator according to a second embodiment, and FIG. 7 is a schematic plan view showing a shielding state of a parallel beam with respect to a rotation angle of a shielding member.

As shown in FIG. 6, the variable optical attenuator 20A of this embodiment comprises a shield member 30A and a driving means 40.

As shown in FIG. 6, the shielding member 30A of the present embodiment is a deformed cam having a similar shape to the shielding member 30 of the above-described first embodiment, and the position of the tip 31A is approximately 1 / e ² at the reference position. The variable shield region in which the attenuation amount is changed by the displacement of the tip 31A is set to be in the range of about 1 / e ² to about -2 / e ² . Further, the tip end 31A is rotated from the reference position to 195 deg while displacing the variable shield region of approximately 1 / e ² to approximately -2 / e ² .

More specifically, as shown in FIG.
The position of 31A is approximately 1 / e of the reference position ²Then, the shielding member 3
0A is approximately 2 / e²~ 1 / e²Shield the area of. This and
Assuming that the rotation angle of the shielding member 30A is 0 deg, FIG.
As shown in (n), the shielding member 30A has the parallel beam 14
Is maximally attenuated, that is, the shielding member 30A is substantially
2 / e²~ Abbreviation -2 / e²When the range of is blocked, the rotation angle
Becomes 195 deg.

Thus, the tip 31A of the shielding member 30A
The change in the attenuation of the parallel beam 14 due to the displacement of
It becomes B to 45 dB. In addition, within this change range of the attenuation amount, for example, if it is used in the range from 15 deg in FIG. 7B to 180 deg in FIG. 7M, 1.87 dB to
It can be used as a variable optical attenuator of 41.41 dB. Of course, it is not limited to this, for example, from 0 deg to 2
You may make it use by rotation of 70 deg.

FIG. 8 shows the relationship between the displacement of the attenuation amount and the rotation angle of the shielding member.

As shown in FIG. 8, the displacement of the attenuation amount with respect to the rotation angle of the shielding member 30A is almost linear, and the attenuation amount increases in proportion to the increase of the rotation angle of the shielding member 30A. I understand.

By setting the variable shielding area by the shielding member 30A to 1 / e ² to -2 / e ² in this way, the parallel beam 1
4 can be easily controlled, that is, the rotation angle of the shielding member 30 can be easily controlled, and the attenuation can be finely adjusted easily and reliably. Further, according to the variable optical attenuator 10A of the second embodiment, 0 to 195 deg or 0.
It can be used in a wide range of 0 dB to 45 dB by rotating 180 degrees.

The driving means 40 for rotating the shielding member 30A is the same as that of the first embodiment described above, but in the first embodiment described above, a slit of 316 Pulse / Rev or more is necessary, whereas in the present embodiment, Attenuation is 1.
At 87 dB, the rotation angle is 15 deg, and at 44.99 dB, it is 195 deg, so the attenuation amount is 1.87 to
When decomposing the range of 44.99 dB in 0.1 dB steps, rotation of about 0.42 deg / step is required.
Therefore, the encoder of this embodiment has 862 Pul.
A slit of se / Rev or more is required.

(Embodiment 3) Embodiments 1 and 2 described above
In the above, the odd-shaped cams are used as the shielding members 30 and 30A, but in the third embodiment, the same eccentric cam as the conventional one is used as the shielding member, and the variable shielding region in which the attenuation amount is changed by the displacement of the tip position is set to the predetermined range. It is a thing.

FIG. 9 is a plan view of the variable optical attenuator according to the third embodiment, and FIG. 10 is a schematic plan view showing a shield state of parallel beams as the shield member rotates.

As shown in the figure, the variable optical attenuator 20B of this embodiment uses an eccentric cam having a perfect circular cylindrical shape as the shielding member 30B and having a rotation shaft eccentric by a predetermined amount. In the shielding member 30B, the tip end 31B has a position of approximately 2 / e ² at the reference position, and the shielding member 30B has a position of 0 / e ^2.
The same as Embodiments 1 and 2 described above, except that the variable shielding region of the tip 31B when rotated by 180 degrees is set to a range of approximately 2 / e ² to approximately −1 / e ² .

The change in the attenuation amount of the parallel beam 14 by the shielding member 30B is approximately 0 dB to approximately 17 dB, and in the present embodiment, the shielding member 30B has a variation of 0 to 180 de.
The parallel beam 14 is rotated by 0 to 16.4 by rotating g.
It was set to attenuate by 3 dB.

FIG. 11 shows the relationship between the displacement of the attenuation amount and the rotation of the shielding member 30B.

As shown in FIG. 11, according to the shielding member 30B according to the third embodiment, the amount of attenuation changes little by little until the rotation angle reaches approximately 75 deg, and changes sharply after the rotation angle exceeds 75 deg. I understand. Therefore, the variable optical attenuator 20B of the present embodiment is more difficult to control the amount of attenuation than the variable optical attenuators 10 and 10A of the first and second embodiments, but the conventional eccentric cam has a transmission light amount of 2 / e ^2- . -2 / e ²
Compared to the case where the entire area of the range is attenuated as a variable shielding area, the area is closer to a linear shape, and the control can be easily performed compared to the conventional case.

The drive means 40 for rotating the shielding member 30B is the same as that of the first embodiment described above, but in the present embodiment, when the attenuation amount is 1.0 dB, the rotation angle is 66 deg, 1 deg.
Since it is 158 deg at 5 dB, rotation of about 0.657 deg / step is required when decomposing the attenuation range of 1.0 to 15 dB in 0.1 dB steps. Therefore, the encoder of the present embodiment has 548P
Although a slit of pulse / Rev or more is required, there is almost no change in the attenuation amount when the rotation angle is in the range of 0 to 66 deg, which causes insufficient gain in the entire servo system. Therefore, when the 480 Pulse / Rev encoder is used, the gain shortage can be resolved by limiting the use range to 1 to 15 dB.

Further, the variable shield attenuator 20B of the present embodiment.
In the above, the variable shield region that is displaced by rotating the shield member 30B by 0 to 180 deg is set to the range of 2 / e ² to -1 / e ² ;
Similarly, the variable shield region may be 1 / e ² to -1 / e ² or 1 / e ² to -2 / e ² . In any case,
It is possible to make the relationship of the displacement of the attenuation amount with respect to the rotation angle of the shielding member 30B closer to linear as compared with the conventional case.

(Other Embodiments) Although the first to third embodiments of the present invention have been described above, the basic configurations of the variable optical attenuator and the device are not limited to those described above.

In the first to third embodiments described above, the shielding member 3
Although the deformed cam and the eccentric cam are used for 0 to 30B, this makes it possible to realize accurate control of the attenuation amount with a small and simple structure. Further, as the shielding member, as shown in FIG. 12, a deformed cam 30C in which the thickness of the peripheral portion of the shaft is different may be used. Note that FIG. 12 is a plan view of the deformed cam.

Further, in the variable optical attenuators 10 to 10B of the above-described first to third embodiments, the parallel beam 14 to be shielded is blocked.
However, in the variable optical attenuator of the present invention that uses a rotating shield member, since the outer peripheral surface is formed of a curved surface, the reflected light of the parallel beam does not return to the optical system, and It is not necessary to decide the orientation of the input side and the output side.
Therefore, since input / output can be performed from either side, installation can be performed easily and reliably.

Furthermore, in the first and second embodiments described above,
Although the rotation angles of the shielding members 30 and 30A are set to 195 deg, they are not particularly limited. For example, when the shielding member is 270 deg.
By rotating, the tip may be displaced in the same variable shield region. Thus, when the tip of the shielding member displaces the same variable shielding region at a wide rotation angle, a finer resolution of the attenuation amount can be realized. Further, by setting the resolution of the attenuation amount to be the same, it is possible to increase the rotation angle for each step, so that the rotation stability can be improved and the rotation angle can be easily controlled.

[0083]

According to the present invention, the damping with respect to the rotation angle of the shielding member which has a substantially cylindrical shape and shields the parallel beam on the outer peripheral surface of the shielding member by the rotation of the driving means to change the attenuation amount. By making the change in the amount substantially linear, it is possible to easily control the rotation angle of the shielding member and easily control the attenuation amount. Further, by limiting the variable shielding area of the shielding member, it is possible to more easily control the rotation with a small rotation angle. Further, the rotating shield member can be easily positioned with respect to the parallel beam.

[Brief description of drawings]

FIG. 1 is a sectional view of a variable optical attenuator including a variable optical attenuator according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an intensity distribution of a parallel beam according to the first embodiment of the present invention.

FIG. 3 is a plan view of the shielding member according to the first embodiment of the present invention.

FIG. 4 is a schematic plan view showing a shield state of parallel beams by the shield member according to the first embodiment of the present invention.

FIG. 5 is a diagram showing the relationship between the displacement of the attenuation amount and the rotation angle of the shielding member according to the first embodiment of the present invention.

FIG. 6 is a top view of a variable optical attenuator according to a second embodiment of the present invention.

FIG. 7 is a schematic plan view showing each shielding state of a parallel beam by the shielding member according to the second embodiment of the present invention.

FIG. 8 is a diagram showing the relationship of the displacement of the attenuation amount with respect to the rotation angle of the shielding member according to the second embodiment of the present invention.

FIG. 9 is a top view of a variable optical attenuator according to a third embodiment of the present invention.

FIG. 10 is a schematic plan view showing a relationship between parallel beam shield states by a shield member according to a third embodiment of the present invention.

FIG. 11 is a diagram showing the relationship between the displacement of the attenuation amount and the rotation angle of the shielding member according to the third embodiment of the present invention.

FIG. 12 is a plan view of a shielding member according to another embodiment of the present invention.

FIG. 13 is a plan view of a variable optical attenuator according to the prior art of the present invention.

FIG. 14 is a diagram showing a relationship of displacement of attenuation amount with respect to a rotation angle of an eccentric cam according to a conventional technique of the present invention.

[Explanation of symbols]

10 Variable optical attenuator 11 optical fiber 12 ferrules 13 Optical system 14 parallel beams 20, 20A, 20B Variable optical attenuator 30, 30A, 30B, 30C Shielding member 31, 31A, 31B Tip 40 drive means 41 Drive motor 42 encoder 43 Interrupter

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02B 26/00-26/08

Claims (15)

(57) [Claims] 1. A variable attenuator provided in a parallel beam region formed between a pair of opposed optical systems for continuously attenuating the parallel beam, wherein the variable attenuator has a substantially cylindrical shape and a driving means The outermost tip of the outermost protruding into the parallel beam by rotation is displaced in a direction orthogonal to the parallel beam to change the attenuation amount of the parallel beam, and the tip of the shield member is displaced. By excluding at least one end on both sides of the parallel beam in the movement direction of the shield member from the shield variable region that shields the parallel beam and changes the attenuation amount, the attenuation amount with respect to the rotation angle of the shield member is reduced. Variable optical attenuator characterized in that the change is substantially linear. 2. The intensity distribution of the parallel beam with respect to the moving direction of the shielding member is Gaussian distribution, and the amount of transmitted light over the displacement direction of the tip position of the shielding member is 2 / e ² --2. when expressed as / e ^2, variable shielding region for changing the attenuation amount by the displacement of the tip end position of the shielding member, are substantially 1 / e ² ~ approximately -1 / e ² with respect to the displacement direction from the reference position A variable optical attenuator characterized in that 3. The intensity distribution of the parallel beam with respect to the moving direction of the shield member is Gaussian distribution, and the amount of transmitted light over the displacement direction of the tip position of the shield member is 2 / e ² --2. when expressed as / e ^2, variable shielding region for changing the attenuation amount by the displacement of the tip end position of the shielding member, are substantially 2 / e ² ~ approximately -1 / e ² with respect to the displacement direction from the reference position A variable optical attenuator characterized in that 4. The intensity distribution of the parallel beam with respect to the moving direction of the shield member is Gaussian distribution, and the amount of transmitted light over the displacement direction of the tip position of the shield member is 2 / e ² --2. In the case of being expressed as / e ² , the variable shield region in which the attenuation amount is changed by the displacement of the tip position of the shield member is approximately 1 / e ² to approximately −2 / e ² from the reference position in the displacement direction. A variable optical attenuator characterized in that 5. The variable light according to claim 1, wherein the shielding member is a deformed cam in which a radius of a portion that shields the parallel beam gradually increases with rotation. Attenuator. 6. The variable light according to claim 5, wherein the shield member is rotated from a reference position by about 150 degrees to about 270 degrees so that its tip position moves within the shield variable region. Attenuator. 7. The attenuation amount of the parallel beam according to claim 6, wherein the amount of attenuation of the parallel beam is approximately 0 dB due to the movement of the range of the variable shield region.
The variable optical attenuator is characterized in that it changes from about 15 dB to about 15 dB. 8. The attenuation amount of the parallel beam according to claim 6, wherein the attenuation of the parallel beam is approximately 0 dB due to the movement of the range of the variable shield region.
The variable optical attenuator is characterized in that it changes from about 45 dB to about 45 dB. 9. The variable optical attenuator according to claim 1, wherein the shielding member has a perfect circular cylindrical shape, and is an eccentric cam whose rotation axis is eccentric by a predetermined amount. 10. The rotating member according to claim 9, wherein the shield member is rotated up to 180 degrees from the reference position so that the tip position of the shield member moves in the range of the variable shield region, and the attenuation amount of the parallel beam is substantially from 0 dB. Variable optical attenuator characterized by varying up to 17 dB. 11. The variable optical attenuator according to claim 1, wherein the drive means is a drive motor, and the drive motor is a pulse motor capable of grasping a rotation angle. . 12. The variable optical attenuator according to claim 1, wherein the drive unit has a drive motor and a rotation angle grasping unit. 13. The variable optical attenuator according to claim 12, wherein the rotation angle grasping means is an encoder provided coaxially with the shielding member and an interrupter grasping a rotation angle of the encoder. 14. The variable optical attenuator according to claim 1, wherein the shielding member is made of a low thermal expansion material having a small thermal expansion coefficient. 15. A variable optical attenuator comprising the variable optical attenuator according to claim 1.