WO2004086119A1

WO2004086119A1 - Variable optical attenuator

Info

Publication number: WO2004086119A1
Application number: PCT/JP2004/003867
Authority: WO
Inventors: Katsuhiko Kurumada; Masatoshi Kanaya; Toshiaki Tamamura; Yoshihiko Suzuki; Tohru Ishizuya; Junji Suzuki; Keiichi Akagawa
Original assignee: Ntt Electronics Corporation; Nikon Corporation
Priority date: 2003-03-27
Filing date: 2004-03-22
Publication date: 2004-10-07
Also published as: JP2004294890A

Abstract

A variable optical attenuator in which problems related to temperature is wiped off principally and attenuation of a light beam passing through an optical waveguide can be controlled to constant regardless of temperature variation. A positional variation detecting mechanism for detecting the inserting position of an inserting plate into the core of the waveguide is provided and the position of the inserting plate is subjected to drive control depending on the position of the inserting plate detected by the positional variation detecting mechanism. Based on a variation in the electrical capacity or the reactance between an electrode provided in the inserting plate driving mechanism and an electrode provided on an inserting plate driving mechanism supporting board or a waveguide holding board, a detecting circuit detects the inserting position of the inserting plate into a slit. Based on the detected position, a feedback control circuit performs drive control of the inserting plate driving mechanism such that the inserting plate is moved to a position where attenuation of the light beam becomes constant.

Description

Variable optical attenuator

Technical field

The present invention relates to a variable optical attenuator used in an optical communication device, and more particularly, to a variable optical attenuator formed in an optical waveguide.

The present invention relates to a variable optical attenuator provided with a detection mechanism for detecting an insertion position of an insertion plate that is inserted into and removed from a slit. Book

Landscape technology

In recent years, optical wavelength multiplexing (optical wavelength multiplexing) has been widely used in optical communication systems. For this reason, wavelength combining using a planar arrayed waveguide circuit has been performed. Waves and demultiplexing often occur. When this circuit is used, a variable optical attenuator is used for the so-called equalizing function that equalizes the input intensity between each wavelength before combining and the output intensity after demultiplexing. ing. The variable optical attenuator uses a microelectromechanical system (MEMS) technology to move a micromirror attached to an optical waveguide into and out of a slit formed in the optical waveguide. The transmitted light amount of the light beam propagating in the wave path can be adjusted.

FI Gs. 7 to 9 show configuration examples of a conventional optical beam variable attenuation regulator using MEMS technology. FIG. 7 is a plan view of the optical beam variable attenuation adjusting device. FI G. 8 is the FI G. 7 in the axial direction of the optical waveguide! ! I The vertical cross-sectional view of the optical beam variable attenuation adjustment device as viewed from the I-line, FIG. 9 shows the optical beam variable attenuation adjustment as viewed from the X-] X-ray of the FI G. 7 perpendicular to the optical waveguide axis. It is a longitudinal cross-sectional view of an apparatus. As shown in FI Gs. 7 to 9, an optical waveguide (core) 101 is formed on the upper surface of an insertion plate supporting board (also referred to as a first substrate) 112. A slit 102 is formed on the way to cross the optical waveguide.

On the other hand, as shown in FI G. 8 and FI G. 9, the insertion plate driving mechanism (also referred to as the second substrate) 114 attached to the insertion plate support substrate 114 The insertion plate 103 is fixed and held at the distal end, and the insertion plate 103 can be inserted into and removed from the slit 102 by the operation of the insertion plate driving mechanism 111. Here, reference numeral 113 denotes a storage part (space segment) for storing the insertion plate driving mechanism 111, and reference numeral 115 designates the insertion plate support substrate 114 for the waveguide support substrate 112. It is a supporting column.

As a driving mechanism of the insertion plate 103, as shown in FIG. 9, for example, an insertion plate driving mechanism 111 which is in a warped condition by stress induction curling is used. Is fixed to the insertion plate driving mechanism support substrate 114 and has a cantilever structure in which the other end is a free end. A voltage is supplied to this cantilever to insert the insertion plate 103 and the waveguide support substrate 1. It is known that the insertion plate 103 is moved into the slit 102 by generating an electrostatic force between the slit 102 and the slit 12 (see FIG. 6 of US Pat. No. 6,195,478). 8, see column 7, line 25 to column 8, line 26).

By the way, in the light beam variable attenuation adjusting device of the type in which the insertion plate is inserted into the slit using the MEMS technology described above, the insertion plate 103 shields the light incident on the optical waveguide 101 so that the transmitted light is attenuated. In order to adjust the amount, the relative position between the optical waveguide 101 and the input plate 103 determines the magnitude of the transmitted light output. In order to obtain a constant attenuation, it is necessary to keep the positions of the optical waveguide 101 and the input plate 103 constant.

However, in the insertion plate driving mechanism 111 that has been warped in advance due to the stress-induced curling described above, the transmitted light output will not be constant due to a change in the warped state due to a temperature change. Of course, the temperature of the stress induced curling The variation due to the degree change depends on how to make the insertion plate driving mechanism 1 1 1. In other words, if the insertion plate driving mechanism 111 is formed so as to minimize the warpage in advance, fluctuations in the warpage due to temperature changes can be reduced, but the amount of warpage is reduced as much as possible. And control of the manufacturing process to keep the amount of warpage within a certain range at all times.Maintaining reproducibility requires strict process control, resulting in a significant cost increase. There are big issues to be addressed.

For example, an optical beam variable attenuator generally requires a change in the degree of light attenuation from 0 dB to 30 dB, that is, a change of about one thousandth. For the purpose of simplicity, the core diameter of the waveguide is set to 10 microns, and the optical attenuation is reduced in the optical beam variable attenuator according to the present invention, which obtains an attenuation effect by shielding the waveguide with the insertion plate. In the case of 10 dB, if the fluctuation of the light beam attenuation due to temperature is to be 0.1 dB per degree, the position of the insertion plate must be suppressed to 0.1 microns per degree.

. In the case of the insertion plate drive mechanism that utilizes the warping state due to the above-described stress-induced curling, it depends on the length of the arm of the insertion plate drive mechanism, but is usually about 1 micron per degree, Extremely strict process control is required to control temperature fluctuations to within 0.1 micron, and this strict process control poses a challenge in manufacturing process control.

Therefore, as a method of avoiding the above-mentioned problem, it is common practice to control the temperature of the light beam variable attenuator to suppress the fluctuation of the light beam attenuation due to the above-mentioned temperature. To control the temperature strictly under the same temperature measurement conditions and suppress the fluctuation to within 0.1 micron at a time, a temperature control of at least ± 0.05 degrees is required. However, such temperature control belongs to high-grade temperature control, causes a cost increase, and cannot be used easily.

Moreover, the temperature factor that determines the amount of warpage of the insertion plate drive mechanism is not only the environmental temperature but also the subtle heat generated by the drive mechanism itself. Adds to the problem of increased disturbance.

Also, in the optical beam variable attenuator, to perform temperature compensation, the variable attenuator The temperature of the insertion plate is measured at multiple representative temperatures in advance, and the relationship between the temperature and the amount of warpage of the insertion plate drive mechanism is given, and the temperature of the insertion plate position is compensated for fluctuations in the actual measured temperature during operation. Is generally performed. This general example is shown in FIG. The optical beam variable attenuator shown in FIG. 10 incorporates a temperature detection circuit 201 and a temperature-to-position conversion control circuit 202. In this case, it is necessary to make the temperature measurement conditions as described above and the measurement temperature conditions when the relationship between the temperature and the amount of warpage described above is given in advance. In addition, when performing temperature measurement twice, there is a drawback that errors are increased due to complicated procedures, such as double errors.

Also, in a variable light beam attenuator, it is usually applied to multiple channels. In this case, it is necessary to include the temperature fluctuation given to the insertion plate of the adjacent channel by the heat flow generated by the heat generated between the optical beam variable attenuators in each channel in the above-mentioned relation between the temperature and the amount of warpage given in advance. Includes the problem that the procedure becomes complicated due to the multi-variable equations and the complexity of the conditions makes it impractical.Therefore, fluctuations due to mutual interference of heat generation between channels must be ignored There is a point that you do not get. Disclosure of the invention

The present invention has been made in view of the above-mentioned points of the prior art, and has as its object to adopt a novel temperature compensation method having a feature of basically eliminating the above-mentioned problem relating to temperature in principle. To provide a variable optical attenuator.

In order to achieve the above object, the present invention provides a light beam propagating in an optical waveguide by inserting and removing an insertion plate (103) in a slit (102) crossing the optical waveguide (101). In a variable optical attenuator that blocks at least a part of the optical fiber and adjusts the amount of transmitted light, the first substrate (1 1 2) on which the optical waveguide and the slit are formed and the insertion plate are held. And an insertion plate driving mechanism (11 1) for moving the insertion plate in the slit, and an insertion plate that is disposed opposite to the first substrate with a predetermined gap so that the insertion plate can be inserted into and removed from the slit, And a second board (114) to which an insertion plate drive mechanism is attached, and a position detection device for detecting an insertion position of the insertion plate into the optical waveguide. Dispensing mechanism (301, 302, 401, 402, 501, 503, 504).

The variable optical attenuator is a feedback circuit (502) connecting the position detection mechanism and the insertion plate driving mechanism for controlling the insertion position of the insertion plate into the optical waveguide in accordance with the output of the position detection mechanism. ).

The position detecting mechanism includes an electrode (301, 401) provided on the second substrate (114) or the first substrate and an electrode (302, 402) provided on the insertion plate driving mechanism (111). By detecting the distance between the electrodes using a change in reactance or a change in capacitance between the electrodes, the insertion position of the insertion plate (103) into the optical waveguide (101) can be detected.

The position detecting mechanism includes a position detecting member (503) that is disposed near the insertion plate driving mechanism (111) and has the same shape and the same characteristics as the insertion plate driving mechanism. (114) A change in reactance or a change in capacitance between the electrode (301, 401) provided on the first substrate or the electrode (504) provided on the position detecting member (503). By detecting the distance between the electrodes, the insertion position of the insertion plate (103) into the optical waveguide (101) can be detected.

The insertion plate driving mechanism (111) is preferably a cantilever member having one end fixed to the second substrate (114) and the insertion plate (103) attached to the other free end. Driven by magnetic force or electrostatic force.

As a technique for controlling the position of the optical waveguide core shielded by the insertion plate, that is, the relative position between the insertion plate and the optical waveguide core, irrespective of temperature fluctuation, detection was performed using the relationship between the temperature and the amount of warpage given in advance. A technique for controlling the degree of warpage to a predetermined amount with respect to temperature is known as a conventional technique. In contrast, in the present invention, as described above, a position change detection mechanism for detecting the insertion position of the insertion plate into the core of the optical waveguide is provided, and the position change detection mechanism detects the position of the insertion plate detected by the position change detection mechanism. Accordingly, the position of the insertion plate is controlled to drive, so that the relative position fluctuation between the insertion plate drive mechanism and the optical waveguide support substrate, which is mainly caused by a temperature change, is directly measured without measuring the temperature. Can detect and read By controlling the relative position change, the attenuation of the light beam transmitted through the optical waveguide can be constantly controlled without being affected by the temperature fluctuation.

Further, as described above, the present invention is based on a change in electric capacitance or a change in reactance between an electrode provided on the insertion plate driving mechanism and an electrode provided on the insertion plate driving mechanism support substrate or the waveguide holding substrate. A feedback circuit that detects the insertion position of the insertion plate into the slit and drives and controls the insertion plate drive mechanism to move the insertion plate to a position where the amount of light beam attenuation is constant based on the detected position. As a result, the light beam attenuation can be kept constant, and the temperature of the device is not controlled or the temperature is not measured. In addition, it is possible to realize an inexpensive optical beam variable attenuation adjustment device that is not affected by temperature fluctuations. BRIEF DESCRIPTION OF THE FIGURES

FI.G. 1 is a plan view showing the configuration of the optical beam variable attenuation adjusting device according to the first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a cross-sectional structure of the light beam variable attenuation adjusting device along the line H-Π in FIG.

FIG. 3 is a plan view showing a configuration of a light beam variable attenuation adjusting device according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a cross-sectional structure of the optical beam variable attenuation adjusting device along the line IV-IV of FIG.

FIG. 5 is a schematic diagram showing an example in which a position control circuit is added to the configuration of the first or second embodiment of the present invention to form a feedback circuit.

FIG. 6 is a diagram showing a configuration of an optical beam variable attenuation adjusting device according to a third embodiment of the present invention. It is a schematic diagram which shows an example to which a circuit was added.

FIG. 7 is a plan view showing a configuration example of a conventional optical beam variable attenuation adjustment device using MEMS technology. FIG. 8 is a cross-sectional view showing a cross-sectional structure of the conventional optical beam variable attenuation adjusting device of FIG. 7 along the -I line.

FIG. 9 is a cross-sectional view showing a cross-sectional structure of the conventional light beam variable attenuation adjustment device along line IX-IX of FIG.

FIG. 10 is a schematic diagram showing a configuration in which a conventional temperature compensation circuit is added to a conventional optical beam variable attenuation adjustment device. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments for carrying out the present invention will be described in detail with reference to the drawings.

First embodiment

FIG. 1 and FIG. 2 show the configuration of the optical beam variable attenuator according to the first embodiment of the present invention, FIG. 1 is a plan view of this device, and FIG. One! ! -It is sectional drawing in Π. Note that the cross-sectional structure along the waveguide of FIG. 1 is substantially the same as that of FIG.

As shown in FIG. 1, the optical beam variable attenuator of the present embodiment includes an optical waveguide core 101 on a waveguide support substrate 112, and an end of the optical waveguide core 101 has an incident side optical fiber 105 and It is connected to the transmission side optical fiber 106. Further, a slit 102 is formed substantially at the center of the optical waveguide core 101 so as to cross the optical waveguide. In FIG. 1, the insertion plate driving mechanism support substrate 114 is not shown for easy understanding of the drawing.

Further, as shown in FIG. 2, an insertion plate driving mechanism housing (space) 113 formed on the upper surface of the waveguide support substrate 112 at a predetermined interval is provided. An insertion plate driving mechanism support substrate 114 is disposed opposite to the waveguide support substrate 112, and the insertion plate 103 includes an insertion plate driving mechanism (actuator unit) supported by the insertion plate driving mechanism support substrate 114. 1) Supported by 1 1.

Note that the spread area of the light beam extends not only in the core part but also in the cluster part in the vicinity thereof, so that the size of the insertion plate 103 is set in consideration of the spread area of the light beam. . Also, for example, a micro mirror can be used as the insertion plate 103. The cantilevered insertion plate driving mechanism 1 1 1 has one upper end fixed to the insertion plate driving mechanism supporting substrate 1 14 and the other free end lifted by stress-induced curling. It moves up and down by electromagnetic force (Lorentz force) or electrostatic force. An insertion plate (also referred to as a shirt) 103 is fixed to the lower surface side of the free end, and the insertion plate 103 is pulled out and inserted in the opposed slit 102 by the vertical movement of the free end. Is A part of the light beam incident from the optical fiber core 108 and guided to the optical waveguide core 101 is shielded by the input plate 103 so that the amount of transmitted light is attenuated. Here, the attenuation of the light beam is naturally determined only by the relative position between the waveguide core 101 and the insertion plate 103.

As described below, if an optical beam variable attenuator capable of detecting the relative position between the insertion plate 103 and the waveguide core 101 is constructed, an insertion plate driving mechanism with a large temperature fluctuation is provided. Also in the apparatus, by performing feedback control using the relative position detection data, it is possible to obtain an effect equivalent to the conventional temperature compensation based on temperature detection in controlling the light beam attenuation.

As shown in FIG. 2, in order to detect the relative position between the insertion plate 103 and the waveguide core 101, the position of the insertion plate 103 is moved on the insertion plate drive mechanism 111. One electrode 302 is arranged near the fixed end, and the other electrode 301 is arranged at an opposing position on the insertion plate driving mechanism support substrate 114, and the pair of electrodes 310 and 3 is arranged. A position change detection circuit 5 that can detect a change in the distance (gap) between the insertion plate driving mechanism 111 and the insertion plate driving mechanism support substrate 114 by measuring the capacitance between 0 and 2. 0 1 is provided. The above-mentioned gap that can be detected by the position change detection circuit 501 and the insertion plate 103 held at the tip of the insertion plate driving mechanism 111 that moves up and down at a certain fixed rate are basically fixed. Since the relationship of the relative position between the optical waveguide at the position and the core 101 becomes constant, The relative position between the insertion plate 103 and the optical waveguide core 101 can be detected by the change detection circuit 501. Actually, the relative position detection of the insertion plate 103 was configured as follows, and an experiment was performed.

First, a bent portion is provided in the middle of the arm of the insertion plate driving mechanism 111, and when the vertical movement of the insertion plate 103 located at the waveguide core 101 is set to 10 microns, the electrode 301 and the electrode Adjust the length of the arm, the strength distribution of the arm and the electrode position, and adjust the electrode area so that the arm of the insertion plate driving mechanism 11 moves about 0.2 μm at the position of the pole 3 0 2. The value of both 0.1 and the electrode 302 was 0.04 square millimeter. At this time, the temperature coefficient of the insertion plate drive mechanism 1 1 is 1 micron. C. In such a configuration, the electric capacity when the insertion plate 103 comes closest to the input plate driving mechanism support substrate 114, and the input plate 103 is driven by 10 microns from this state. When the difference from the capacitance when the substrate was separated from the mechanism support substrate 114 was measured, a change of 45 picofarads was obtained. As a result, the ratio of the capacitance to the movement of the input plate becomes 0.2 micron Z picofarad, so that with the above temperature coefficient, an effect equivalent to detection of 0.2 ° C per picofarad can be obtained. Can be.

Therefore, with the configuration shown in FIG. 2, temperature measurement is not required, and the position of the insertion plate 103 can be easily detected. In addition, each position of a plurality of insertion plates can be detected. Therefore, the position change detection circuit 501 according to the present invention can be said to be advantageous as a position detection device for a multi-channel optical beam variable attenuator. Second embodiment

Next, a description will be given of a second embodiment of the present invention using FIGS. 3 and 4 in a light beam variable attenuating device having a configuration as shown in FIGS. 8 and 9. It is more preferable to directly capture the relative position between the insertion plate 103 and the waveguide core 101. Therefore, in the second embodiment of the present invention shown in FIG. 3 and FIG. 4, The electrode 402 on the insertion plate driving mechanism 1 1 1 is placed near the pole of the insertion plate 103, and the other electrode 410 facing the electrode 402 is placed on the waveguide support substrate 112. It is formed on the edge of the slit 102.

In this electrode arrangement, the change in electric capacitance is smaller than that in the first embodiment, but the change in the relative position of the insertion plate 103 with respect to the optical waveguide core 101 can be sufficiently grasped. Even in such a configuration, the relative position between the input plate 103 and the waveguide core 101 is detected via the electrodes 401 and 402, and the electromagnetic force (port 1) is detected using the relative position detection data. By performing feedback control for adjusting the Lenz force or the electrostatic force, a control effect equivalent to the conventional temperature compensation based on temperature detection can be obtained in the optical attenuation control. In the first and second embodiments described above, the change in the relative position of the structure in the optical beam variable attenuation adjustment device is detected as the change in the electric capacity. However, the position detection is not limited to this. Instead, a method of detecting an inductive change in reactance can be used. Example of control system

As shown in FIG. 5, the electrode 310 is used as a position detecting mechanism for detecting the relative position between the input plate 103 and the waveguide core 101 by utilizing the fluctuation of the electric capacity and the like as described above. A feedback circuit is configured by using the electrode 302 (or the electrode 401 and the electrode 402), the position change detection circuit 501, and the insertion plate position control circuit 5-2. In accordance with the feedback data of the feedback circuit, the insertion plate position control circuit 502 controls the movement of the insertion plate 103 to a position corresponding to the amount of attenuation of the light beam. Drive one. By this feedback control, according to the present invention, the temperature and the position measured in advance by detecting the temperature without using the conventional method of performing the temperature compensation by controlling the temperature to be constant based on the temperature detection can be used. Therefore, it is possible to realize a light beam attenuation adjustment device that is not affected by temperature without using a conventional method of compensating for the temperature by correcting the position of the insertion plate from the phase relationship.

Using the detection device according to the first or second embodiment of the present invention, the feedback circuit shown in FIG. When the movement position of the insertion plate 103 was controlled by the road, the output fluctuation with respect to the temperature fluctuation could be kept within 0.15 dB / ° C. Third embodiment

Further, in the case of configuring a more integrated light beam variable attenuation adjusting device, for example, when it is necessary to make a large change in electric capacity for position detection, or it is not possible to provide a position detecting means for each channel. In this case, as shown in the third embodiment of the present invention in FIG. 6, the device is not driven by the electromagnetic force, but has the same shape as the insertion plate driving mechanism 111, and The position detecting mechanism (monitor dummy mechanism) 503 having a large change in electric capacity by increasing the area of 504 is arranged near the insertion plate driving mechanism 111. It is more preferable that the position detecting mechanism 503 be formed in consideration of not only the shape and size of the insertion plate driving mechanism 111 but also the weight and mounting position of the insertion plate 103.

The position change due to the temperature change of the position detecting mechanism 503 is detected by the position change detecting circuit 501 as a change in electric capacity, and in response to this detection, the insertion plate driving control circuit 505 with the position correcting circuit is used.位置 The position of the insertion plate 103 is controlled by controlling the drive of the insertion plate driving mechanism 111.相対 Corrects the relative position between the insertion plate 103 and the optical waveguide core 101.By using such an insertion plate drive control circuit 505 with a position correction circuit, position compensation is performed without temperature measurement. be able to.

In the present embodiment, when the area of the electrode 504 arranged on the position detecting mechanism 503 is set to 0.25 square millimeter, the position detecting mechanism 503 becomes the same as the insertion plate driving mechanism 1 1 1. When moved by 10 microns with respect to a temperature change of 0 ° C., it was possible to change the capacitance to 110 picofarads. In the optical beam variable attenuation adjustment device using the position detection mechanism 503 to form a feedback control system as shown in FIG. 6, the temperature fluctuation of the light intensity attenuation is reduced to 0.1 dB without a compensation circuit for detecting the temperature. It could be controlled within Z ° C. Other embodiments

Although the preferred embodiment of the present invention has been described by way of example, the embodiment of the present invention is not limited to the above-described embodiment. Various modifications such as replacement, change, addition, increase / decrease in number, and change in shape are all included in the embodiments of the present invention. For example, in the above-described embodiment of the present invention, the position detecting mechanism of the insertion plate detects the distance between the electrodes by using a change in the capacitance. However, the present invention is not limited to this, and various reactances between the electrodes The distance between the electrodes may be detected using the change. Further, in the above-described embodiment, a single-lens force can be used as the driving force of the insertion plate driving mechanism. However, the present invention is not limited to this. For example, electrostatic force driving may be used. Further, in the above-described embodiment, the insertion plate driving mechanism using the cantilever is illustrated, but various forms of actuators may be applied. Also, the insertion plate is not limited to a mirror, but may be a shielding plate that absorbs light.

Claims

The scope of the claims

1. A variable optical attenuator that adjusts the amount of transmitted light by inserting and removing an insertion plate into and out of a slit that crosses the optical waveguide to block at least a part of the light beam that propagates in the optical waveguide.

A first substrate on which the optical waveguide and the slit are formed,

An insertion plate driving mechanism for holding the insertion plate and moving the insertion plate in the slit, and the insertion plate is arranged to face the first substrate with a predetermined gap so that the insertion plate can be inserted into and removed from the slit, A second substrate to which the insertion plate driving mechanism is attached;

A position detection mechanism that detects an insertion position of the insertion plate into the optical waveguide;

A variable optical attenuator comprising:

2. A variable optical attenuator which inserts and removes an insertion plate into and from a slit crossing the optical waveguide to block at least a part of the light beam propagating through the optical waveguide and adjust the amount of transmitted light.

A first substrate on which the optical waveguide and the slit are formed,

An insertion plate driving mechanism that holds the insertion plate and moves the insertion plate in the slit; and an insertion plate driving mechanism that is arranged to face the first substrate with a predetermined gap so that the insertion plate can be inserted into and removed from the slit. A second substrate to which the insertion plate driving mechanism is attached, and

A position detection mechanism for detecting an insertion position of the insertion plate into the optical waveguide, and controlling the insertion position of the insertion plate to the optical waveguide in accordance with an output of the position detection mechanism, A feedback circuit connecting the position detection mechanism and the insertion plate drive mechanism; and

A variable optical attenuator comprising:

(3) In a variable optical attenuator, an insertion plate is inserted into and removed from a slit for dividing an optical waveguide, thereby blocking at least a part of a light beam propagating in the optical waveguide and adjusting the amount of transmitted light.

A first substrate on which the optical waveguide and the slit are formed,

An insertion plate driving mechanism that holds the insertion plate and moves the insertion plate in the slit; and an insertion plate that is disposed to face the first substrate with a predetermined gap so that the insertion plate can be inserted into and removed from the slit. A second substrate to which the insertion plate driving mechanism is attached, and

A position detection mechanism that detects an insertion position of the insertion plate in the optical waveguide,

A feedback circuit that connects the position detection mechanism and the insertion plate drive mechanism, controlling the insertion position of the insertion plate into the optical waveguide in accordance with an output of the position detection mechanism, and

The insertion plate driving mechanism is a cantilever member having one end fixed to the second substrate and the insertion plate attached to the other free end, and driven by electromagnetic force or electrostatic force. Variable optical attenuator.

4. The position detecting mechanism detects a distance between the electrodes by using a change in reactance between an electrode provided on the second substrate and an electrode provided on the insertion plate driving mechanism, thereby obtaining the distance between the electrodes. 4. The variable optical attenuator according to any one of claims 1 to 3, wherein a position at which the insertion plate is inserted into the optical waveguide is detected.

5. The position detection mechanism detects a distance between the electrodes by using a change in reactance between an electrode provided on the first substrate and an electrode provided on the insertion plate driving mechanism, whereby the insertion is performed. 4. The variable optical attenuator according to any one of claims 1 to 3, wherein a position at which a plate is inserted into the optical waveguide is detected.

6. The position detection mechanism is configured to drive the electrode provided on the second substrate and the insertion plate. Claims 1 to 3 wherein the insertion position of the insertion plate into the optical waveguide is detected by detecting a distance between the electrodes using a change in capacitance between the electrodes provided in the mechanism. The variable optical attenuator according to any one of the above.

7. The position detection mechanism detects an inter-electrode distance by using a change in electric capacitance between an electrode provided on the first substrate and an electrode provided on the insertion plate driving mechanism, 4. The variable optical attenuator according to claim 1, wherein a position at which the insertion plate is inserted into the optical waveguide is detected.

8. The position detecting mechanism is disposed near the insertion plate driving mechanism, and includes a position detecting member having the same shape and the same characteristics as the insertion plate driving mechanism, and the first substrate or the second substrate. Detecting the insertion position of the insertion plate into the optical waveguide by detecting a distance between the electrodes using a change in reactance between the electrode provided on the substrate and the electrode provided on the position detection member. The variable optical attenuator according to any one of claims 1 to 3, characterized in that:

9. The position detecting mechanism is disposed near the insertion plate driving mechanism, includes a position detecting member having the same shape and the same characteristics as the insertion plate driving mechanism, and the first substrate or the second substrate. By detecting the distance between the electrodes using the change in electric capacity between the electrode provided on the substrate and the electrode provided on the position detecting member, the insertion position of the insertion plate into the optical waveguide is detected. The variable optical attenuator according to claim 1, wherein the variable optical attenuator is provided.