JP2000131626A - Variable light attenuator and light attenuating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized, simply constituted, power-saving variable light attenuator with less wavelength dependency for an attenuation quantity. SOLUTION: The attenuator is provided with a 1st optical fiber 1 for transmitting incident light, a lens 3 for image-converting the converged luminous flux 8 outgoing from the 1st optical fiber 1 to a collimated luminous flux 5, a mirror 4 for reflecting the collimated luminous flux 5 outgoing from the lens 3 toward the lens 3, a micromachine 10 with a movable part for moving the direction of the optical axis of the mirror 4 by a driving part 11, and a 2nd optical fiber 2 which is installed in a position where the light reflected by the mirror 4 may be made incident. Then, the transmitted outgoing light is adjusted by the movement 70 of the reflecting direction of the reflected light in accordance with the movement 7 of the optical axis of the mirror 4 due to the displacement 6 of the movable part of the micromachine 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical attenuator, and more particularly to a variable optical attenuator using a silicon micromachine.

[0002]

2. Description of the Related Art An optical attenuator is a device for giving a constant attenuation to light propagating in an optical fiber or a space, and is used for evaluating the performance of an optical device or a light receiving element and adjusting a propagation loss. Conventional variable optical attenuators required many components. For example, such a variable optical attenuator is described in Nakata et al., "Magneto-optical Variable Optical Attenuator" (1997 IEICE Electronics Society Conference C-3-48). FIG. 5 is a schematic configuration example of a conventional variable optical attenuator. Variable optical attenuator 1
00 is an optical fiber 101, 102, a lens 103, 1
04, Faraday rotator 105, polarization separation element 106,
107 and an electromagnet 109.
By rotating the Faraday rotator, the amount of irradiation light of the optical fiber 101 to the optical fiber 102 is adjusted to achieve the purpose of optical attenuation.

[0003]

However, such a conventional variable optical attenuator has a problem that it is large and expensive. The reason is that the number of parts is large and the configuration is complicated.

Another problem is that the power consumption is large. The reason is that the power consumption of the electromagnet is large.

Further, there is a problem that the wavelength dependence of the attenuation is large. The reason is that the rotation angle of the Faraday rotator has wavelength dependence.

An object of the present invention is to solve the above problems and to provide a variable optical attenuator which is small in size, has a simple structure, consumes little power, and has little wavelength dependence of attenuation.

[0007]

SUMMARY OF THE INVENTION A variable optical attenuator according to the present invention is a variable optical attenuator for providing a predetermined attenuation to light propagating through one of an optical fiber and a space, and a mirror section for reflecting incident light. Is provided on the movable part of the micromachine,
The propagation of the emitted light is adjusted by the movement of the reflection direction of the reflected light accompanying the movement of the optical axis of the mirror unit accompanying the displacement of the movable unit.

As a specific mode, a first optical fiber for transmitting incident light, a lens for converting a convergent light beam emitted from the first optical fiber into a parallel light beam, and a parallel light beam emitted from the lens A micromachine having a mirror unit for reflecting a light beam in the direction of the lens, a movable unit capable of moving the direction of the optical axis of the mirror unit, and a position where reflected light from the mirror unit can enter via the lens And a second optical fiber disposed at the second position.

Preferably, the micromachine is a silicon micromachine which is micromachined on a silicon substrate and has a movable portion capable of electrostatically performing a displacement operation. In the silicon micromachine, the movable portion has a hinge portion on a main body. The movable part may be a micro-hinge type micro machine in which the movable part can rotate around the hinge, and the outer periphery of the movable part is a displaceable diaphragm structure connected to the main body. A diaphragm type micro machine which can be moved in the direction of the drive electrode by a drive electrode arranged close to the center of the movable portion may be used.

According to the optical attenuating method of the variable optical attenuator of the present invention, a convergent light beam emitted from a first optical fiber that propagates incident light is image-converted into a parallel light beam by a lens, and the parallel light beam emitted from the lens is converted into a parallel light beam. The light is reflected in the direction of the lens by a mirror disposed at the focal position of the lens, the reflected light from the mirror is image-converted into a convergent light beam by the lens, and the convergent light beam image-converted by the lens is incident on the second optical fiber. The amount of reflected light incident on the second optical fiber is adjusted by moving the direction of the optical axis of the mirror with a micromachine.

With this configuration, the number of components is reduced, resulting in a small and inexpensive variable optical attenuator. The hinge-type micromachine and the diaphragm-type micromachine consume less power, so that the overall power consumption is reduced. Since the wavelength dependence of the reflectance of the total reflection film of the mirror is small, the wavelength dependence of the attenuation is reduced.

[0012]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a variable optical attenuator according to a first embodiment of the present invention. The present invention is a small and high-performance variable optical attenuator using a silicon micromachine.

More specifically, the variable optical attenuator of the present invention includes optical fibers 1 and 2, a lens 3, and a micromachine 10 having a mirror 4 and a driving unit 11. The convergent light beam 8 emitted from the optical fiber 1 is image-converted into a parallel light beam 5 by the lens 3. Thereafter, the parallel light beam 5 is totally reflected by the reflection surface of the mirror 4 and returns to the lens 3 again. After image conversion, the light beam becomes a convergent light beam 9 and is coupled to the optical fiber 2.

When the mirror 4 is moved in the direction of arrow 6, the parallel light beam 5 is shifted in the direction of arrow 7, and the convergent light beam 9 is shifted in the direction of arrow 7.
Shift in the direction of 0.

The coupling loss between the optical fiber 1 and the optical fiber 2 increases in proportion to the shift amount of the convergent light flux 9,
Since the shift amount of the convergent light beam 9 is proportional to the shift amount of the mirror 4, the coupling loss between the optical fiber 1 and the optical fiber 2 can be controlled by controlling the shift amount of the mirror 4. Functions as a vessel.

A specific configuration example of the present invention will be described in detail with reference to FIG. The optical fiber 1 and the optical fiber 2 are single mode optical fibers. The lens 3 is a lens that converts an image of the convergent light beam 8, which is light emitted from the fiber 1, into a parallel light beam 5, and converts the parallel light beam 5 into an image of a convergent light beam 9. The lens 3 is an aspheric lens, and its focal length is 4 mm. The beam diameter of the parallel light beam 5 is 200 μm.
m.

The micromachine 10 is a micro hinge type silicon micro machine mainly composed of a mirror 4 and a drive unit 11. The structure and operation of the micro hinge type silicon micro machine are, for example, Ric.
hard S.M. Muller, Surface Mi
cromachining for Micropho
tonics (MOEMOS97Technical)
As described in Digest pp109-113), the semiconductor device is manufactured in a small size and precisely by applying a semiconductor manufacturing technology.

The mirror 4 has a light reflecting mirror formed by depositing a dielectric film on silicon as a base material, and totally reflects incident light.

The positional relationship between the lens 3 and the mirror 4 is such that the distance from the principal plane 12 of the lens 3 to the reflecting surface of the mirror 4 is equal to the focal length of the lens 3 and the micromachine 10
When the optical fibers 1 and 2 are not operated, the principal plane 12 and the reflection surface of the mirror 4 are arranged in parallel.
Are arranged symmetrically with respect to the lens optical axis 13, and 2
The distance between the two fibers is about 125 μm.

The operation of the present invention will be described with reference to FIGS. FIGS. 1 and 2 are schematic structural diagrams of a variable optical attenuator according to a first embodiment of the present invention.
Shows a state when the micromachine is not operating, and FIG.
This shows the state during operation of the micromachine.

The convergent light beam 8 emitted from the optical fiber 1 is
The image is converted into a parallel light beam 5 by the lens 3. Parallel beam 5
Is then totally reflected by the reflecting surface of the mirror 4 and again
After the image conversion, a convergent light flux 9 is formed and coupled to the optical fiber 2.

Next, referring to FIG.
Operation when the mirror 4 is moved in the direction of the arrow 6 by driving 0 will be described. Convergent light beam 8 emitted from optical fiber 1
Is converted into a parallel light beam 5 by the lens 3. The parallel light beam 5 is then totally reflected by the reflecting surface of the mirror 4, but the parallel light beam 5 reflected in the direction of arrow 7 is not reflected since the normal 130 of the mirror 4 does not coincide with the optical axis 13 of the lens 3. The light beam 9 is shifted and the convergent light beam 9 is shifted in the direction of the arrow 70, so that the light beam 9 is not coupled to the optical fiber 2.

The shift amount of the parallel light beam 5 is proportional to the displacement amount of the mirror 4, and the coupling loss between the optical fiber 1 and the optical fiber 2 is approximately proportional to the square of the shift amount of the parallel light beam 5. I do. That is, by changing the driving amount of the mirror 4,
Since the coupling loss between the optical fiber 1 and the optical fiber 2 can be changed, the present invention operates as a variable optical attenuator.

Explaining in a specific embodiment, when the voltage applied to the micromachine driving unit 11 is 0 V, there is no displacement of the mirror 4 and the coupling loss between the optical fiber 1 and the optical fiber 2 is 0.7 dB. On the other hand, when the voltage applied to the micromachine driving unit 11 was 20 V, the mirror 4 shifted by 1 deg in the direction of the arrow 6, and as a result, the coupling loss between the optical fiber 1 and the optical fiber 2 became 20 dB.

Next, a second embodiment of the present invention will be described with reference to FIGS. 3 and 4 are schematic diagrams of a variable optical attenuator according to a second embodiment of the present invention. FIG. 3 shows a state where the micromachine is not operating, and FIG. This shows the state during operation.

In the second embodiment, a diaphragm micromachine 30 is used instead of the microhinge silicon micromachine 10 of the first embodiment.
Other configurations are the same as those of the first embodiment.

The micromachine 30 includes a drive electrode 31 and a diaphragm 40. The area of the drive electrode 31 is
It is sufficiently smaller than the diaphragm 40.

On the end face of the diaphragm 40, a light reflecting mirror portion 34 is formed similarly to the mirror 4 of the above embodiment, and totally reflects incident light.

FIG. 3 shows a state where the micromachine 30 is not operating. When the diaphragm 40 is not in operation, the normal line of the mirror portion 34 and the optical axis of the lens 23 are parallel to each other. Therefore, the diaphragm 40 has the same form as that of the previous embodiment when the micromachine is not in operation.

FIG. 4 shows a state when the micromachine 30 is operated. When a voltage is applied to the drive electrode 31, the diaphragm 40 is displaced in the direction of the arrow 26,
Since the areas of the drive electrode 31 and the diaphragm 40 are different,
It is not uniformly displaced, but deforms like a bow as shown in FIG.

Therefore, in a portion of the diaphragm 40 that is far from the drive electrode 31, the normal 330 of the mirror portion 34 has an inclination.
By arranging the components so that the light is incident, it becomes possible to operate the variable attenuator equivalent to the previous embodiment.

Although the embodiment of the present invention has been described using a silicon micromachine, the invention is not limited to the silicon micromachine, and any micromachine suitable for this purpose may be used.

[0033]

As described above, the first effect of the present invention is that it is small and inexpensive. The reason is that the number of components is reduced by using a micromachine.

The second effect is that power consumption is small. The reason is that the power consumption of the hinge type micromachine or the diaphragm type micromachine is small.

A third effect is that the wavelength dependence of the attenuation is small. The reason is that the reflectance wavelength dependence of the total reflection film of the mirror is small.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a variable optical attenuator according to a first embodiment of the present invention, showing a state where a micromachine is not operating.

FIG. 2 is a schematic configuration diagram of the variable optical attenuator according to the first embodiment of the present invention, showing a state when the micromachine operates.

FIG. 3 is a schematic configuration diagram of a variable optical attenuator according to a second embodiment of the present invention, showing a state where the micromachine is not operating.

FIG. 4 is a schematic configuration diagram of a variable optical attenuator according to a second embodiment of the present invention, showing a state when a micromachine is operating.

FIG. 5 is a schematic configuration example of a conventional variable optical attenuator.

[Explanation of symbols]

 1, 2, 21, 22, 101, 102 Optical fiber 3, 23, 103, 104 Lens 4, 34 Mirror 5, 25 Parallel light flux 6, 7, 26, 34, 70, 270 Moving direction 8, 9, 28, 29 Convergent light flux 10, 30 Micromachine 11 Drive unit 13, 33 Lens optical axis 31 Drive electrode 100 Variable optical attenuator 105 Faraday rotator 106, 107 Polarization separation element 109 Electromagnet 130, 330 Mirror normal

Claims (6)

[Claims] 1. A variable optical attenuator for applying a predetermined attenuation to light propagating in one of an optical fiber and a space, wherein a mirror unit for reflecting incident light is provided on a movable unit of the micromachine, and The variable light attenuator, wherein the transmitted light is adjusted by the movement of the reflected light in the direction of reflection caused by the movement of the optical axis of the mirror unit accompanying the displacement of the mirror unit. 2. A first optical fiber for transmitting incident light, a lens for converting a convergent light beam emitted from the first optical fiber into a parallel light beam, and a parallel light beam emitted from the lens for the lens. The mirror unit reflecting in the direction; the micromachine having the movable unit capable of moving the direction of the optical axis of the mirror unit; and the reflected light from the mirror unit can be incident via the lens. The variable optical attenuator according to claim 1, further comprising: a second optical fiber disposed at a position. 3. The variable light attenuation according to claim 1, wherein the micromachine is a silicon micromachine that is micromachined on a silicon substrate, and the movable unit is capable of performing a displacement operation electrostatically. vessel. 4. The variable light according to claim 3, wherein the silicon micromachine is a microhinge type micromachine in which the movable part is connected to a main body by a hinge part, and the movable part is capable of rotating around the hinge. Attenuator. 5. The silicon micro-machine has a displaceable diaphragm structure in which an outer periphery of the movable portion is connected to a main body, and a driving portion in which a central portion of the movable portion is arranged close to the vicinity of the center of the movable portion. The variable optical attenuator according to claim 3, wherein the variable optical attenuator is a diaphragm-type micromachine movable in a direction of the driving electrode by an electrode. 6. A mirror which is arranged at a focal position of the lens by converting a convergent light beam emitted from the first optical fiber which propagates the incident light into a parallel light beam by a lens, and converting the parallel light beam emitted from the lens to a focal position of the lens. The reflected light from the mirror is image-converted into a convergent light beam by the lens, and the convergent light beam image-converted by the lens is made incident on a second optical fiber. The optical axis of the mirror Wherein the amount of the reflected light incident on the second optical fiber is adjusted by moving the direction of the reflected light by a micromachine.