JP2013104918A - Wavelength selection switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength selection switch capable of correcting a deviation of the center wavelength of filter characteristics.SOLUTION: A wavelength selection switch 300 includes: an input port 301 to which a wavelength-multiplexed optical signal is input; an output port 302 to which the optical signal is output; a demultiplexing/multiplexing device 304 for demultiplexing and multiplexing the optical signal; an optical deflector array 306 capable of deflecting the optical signal at each wavelength; and an optical member 303 for coupling the input port 301 and the output port 302 through the demultiplexing/multiplexing device 304 and the optical deflector array 306. The optical deflector array 306 has a plurality of optical deflectors 305 arrayed in the demultiplexing direction of the demultiplexing/multiplexing device 304, and an optical detection section 307 for receiving an optical signal deviating from the optical deflector 305, and outputting an electric signal in which the light quantity of the received optical signal is reflected. The wavelength selection switch 300 further includes a position changing section 309 capable of changing the position of the optical deflector array 306, and a control section 308 for servo-controlling the position changing section 309 based on the result detected by the optical detection section 307.

Description

  The present invention relates to a wavelength selective switch.

  In the optical fiber communication industry, wavelength division multiplexing (WDM) technology is used to cope with an increase in communication data volume. One of optical devices for constructing a large-capacity optical communication system using WDM technology is a wavelength selective switch (WSS). The wavelength selective switch is, for example, a device that can distribute an input wavelength multiplexed signal (wavelength multiplexed optical signal) to different outputs for each wavelength. For this purpose, the wavelength selective switch includes a demultiplexing element that demultiplexes the optical signal and a plurality of optical deflectors that respectively deflect the demultiplexed beams having a plurality of wavelengths.

  Such a wavelength selective switch is disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-148429.

JP 2007-148429 A

  In order that no error data is generated in the optical signal communicated through the wavelength selective switch, the filter characteristic of the wavelength selective switch needs to match the standard wavelength of ITU-GRID and wide. It is desirable to have a transmission bandwidth. Here, the filter characteristic corresponds to, for example, the wavelength range of the light beam deflected by each optical deflector.

  The filter characteristics of the wavelength selective switch can change due to environmental changes such as temperature changes. For this reason, the center of the filter characteristics may deviate from the ITU-GRID (hereinafter, this state is referred to as a center wavelength shift of the filter characteristics). Such a situation causes a deterioration in the quality of the optical signal communicated through the wavelength selective switch.

  Conventional wavelength selective switches including the wavelength selective switch disclosed in Japanese Patent Application Laid-Open No. 2007-148429 have not been proposed with a function of correcting the center wavelength shift of the filter characteristics in consideration of such a situation. .

  An object of the present invention is to provide a wavelength selective switch capable of correcting a center wavelength shift of a filter characteristic caused by an environmental change.

  A wavelength selective switch according to the present invention includes: an input port to which a wavelength-multiplexed optical signal is input; an output port from which the optical signal is output; a demultiplexer / multiplexer that demultiplexes and multiplexes the optical signal; An optical deflector array that can deflect the optical signal for each wavelength, and an optical member that couples the input port and the output port via the branching multiplexer and the optical deflector. The optical deflector array includes a plurality of optical deflectors arranged in a demultiplexing direction of the demultiplexer / multiplexer and a light detection unit that outputs an electric signal reflecting the received light quantity. The wavelength selective switch further includes a position changing unit that can change the position of the optical deflector array, and a control unit that servo-controls the position changing unit based on a detection result by the light detection unit.

  According to the present invention, there is provided a wavelength selective switch capable of correcting a center wavelength shift of a filter characteristic caused by an environmental change.

The relationship between the filter characteristic of a wavelength selective switch and the optical signal communicated through a wavelength selective switch is shown. It is a conceptual diagram explaining the quality degradation of the optical signal by the center wavelength shift of filter characteristics. The filter characteristic, the positional relationship between the optical deflector and the beam spot in the state where the center wavelength shift of the filter characteristic does not occur is shown. It is a conceptual diagram explaining generation | occurrence | production of the center wavelength shift of the filter characteristic by the position shift of an optical deflector array. It is a conceptual diagram explaining generation | occurrence | production of the center wavelength shift of the filter characteristic by the position shift of a beam spot. The flow of the generation | occurrence | production mechanism of the center wavelength shift of a filter characteristic is shown. The structure of the wavelength selective switch of 1st Embodiment is shown typically. The structure of the optical deflector array of the wavelength selective switch of 1st Embodiment is shown typically. The structure of the control part of the wavelength selective switch of 1st Embodiment is shown typically. It is a figure explaining the principle of the center wavelength shift detection of the filter characteristic in 1st Embodiment. The operation | movement flow of the center wavelength shift correction of the filter characteristic in the wavelength selective switch of 1st Embodiment is shown. The structure of the optical deflector array of the wavelength selective switch of 2nd Embodiment is shown typically. A part of the optical deflector array of the wavelength selective switch of the second embodiment is shown enlarged. The structure of the control part of the wavelength selective switch of 2nd Embodiment is shown typically. The structure of the optical deflector array of the wavelength selective switch of 3rd Embodiment is shown typically. A part of the optical deflector array of the wavelength selective switch of the third embodiment is schematically enlarged and shown. The structure of the control part of the wavelength selective switch of 3rd Embodiment is shown typically. The operation | movement flow of the wavelength selective switch of 3rd Embodiment is shown typically.

  Prior to the description of the embodiment of the present invention, first, the generation mechanism and the influence of the center wavelength shift of the filter characteristics in the wavelength selective switch will be described.

  As described above, the filter characteristic of the wavelength selective switch needs to have its center wavelength matched with ITU-GRID, and the filter characteristic of the wavelength selective switch is desired to have a wide transmission bandwidth. .

  The relationship between the filter characteristics of the wavelength selective switch and the optical signal communicated through the wavelength selective switch is shown in FIG. FIG. 1 shows a filter characteristic corresponding to one of ITU-GRID and an optical signal (a beam of one wavelength that has been demultiplexed). FIG. 1A shows an example in which the filter characteristics have a wide bandwidth, and FIG. 1B shows an example in which the filter characteristics have a narrow bandwidth. As shown in FIG. 1A, when the filter characteristic has a wide bandwidth, the signal light is transmitted without being blocked. On the other hand, as shown in FIG. 1B, when the filter characteristic has a narrow bandwidth, the signal light is the wavelength component of the optical signal corresponding to the portion within the ellipse in the figure. Is cut. This causes a reduction in the quality of the optical signal to be communicated and causes error data to be generated.

  Further, as shown in FIG. 2, when the center wavelength of the filter characteristic is deviated, the wavelength component of the optical signal corresponding to the portion in the circle of the signal light is cut. This causes a reduction in the quality of the optical signal to be communicated and causes error data to be generated.

  Through the research, the present inventor found that the center wavelength of the filter characteristics can be shifted due to disturbances such as vibration shock and temperature change, and concluded that it is necessary to manage the shift between the center wavelength of the filter characteristics and ITU-GRID. Reached.

  The center wavelength of this filter characteristic is determined by the position of the beam spot of light incident on the optical deflector and its mirror in the wavelength selective switch. When the center of the beam spot having a wavelength of ITU-GRID comes to the center of the optical deflector, the center wavelength of the filter characteristic coincides with ITU-GRID (see FIG. 3). Therefore, the cause of the center wavelength shift of the filter characteristics may be a position shift of the optical deflector array or a position shift of the beam spot.

  As one of the causes of the center wavelength shift of the filter characteristics, the installation position shift of the optical deflector array due to disturbance such as environmental temperature change can be considered. Normally, the optical deflector array is arranged so that the center of each optical deflector in the array coincides with the center of the beam spot of the input light of ITU-GRID. Therefore, as shown in FIG. 4, when the optical deflector array is misaligned, the center wavelength of the transmission band of the filter characteristics is shifted from the center wavelength of the band of the signal light. When this deviation is large, a part of the band of the signal light protrudes outside the transmission band of the filter characteristics, and thus a part of the wavelength component of the optical signal is cut. This causes a decrease in the quality of the optical signal and causes a data error.

  The same situation also occurs when the position of the beam spot of the input light to the optical deflector is shifted due to deformation or displacement of optical components such as a demultiplexing element and a lens (see FIG. 5). As shown in FIG. 5, when the position of the beam spot of the input light to the optical deflector deviates from the center of the optical deflector, the center of the beam spot deviates from the center wavelength of the transmission band of the filter characteristics. Also in this case, as in the case where the optical deflector array is displaced, a part of the signal light band protrudes outside the transmission band of the filter characteristics, so that a part of the wavelength component of the signal light is cut. As a result, the quality of the optical signal is deteriorated and a data error occurs.

  To summarize the above, the flow of the generation mechanism of the center wavelength shift of the filter characteristic is as shown in FIG. First, disturbances such as environmental changes occur. As a result, deformation or misalignment of optical components (including the optical deflector) in the wavelength selective switch occurs. Then, a spatial shift of the optical path in the wavelength selective switch occurs. For this reason, a relative displacement between the optical deflector and the beam spot occurs. Then, a center wavelength shift of the filter characteristic occurs. Thereby, a part of the optical signal is cut. As a result, the quality of the optical signal is degraded.

<First Embodiment>
The wavelength selective switch according to the first embodiment of the present invention will be described below.
(Constitution)
As illustrated in FIG. 7, the wavelength selective switch 300 according to the first embodiment includes an input port 301 to which a wavelength-multiplexed optical signal is input, an output port 302 to which an optical signal is output, a demultiplexing and optical signal. A demultiplexer / multiplexer 304 such as a grating to be multiplexed, an optical deflector array 306 that can deflect an optical signal for each wavelength, an input port 301 and an output port 302, and a demultiplexer / multiplexer 304 and an optical deflector array 306. And an optical member 303 such as a lens to be coupled with each other.

  The demultiplexer / multiplexer 304 has a function of dividing the optical signal input from the input port 301 into a plurality of beams having different wavelengths. Each beam has a wavelength broadening, and its center wavelength matches ITU-GRID.

  The optical deflector array 306 includes a plurality of optical deflectors 305 and a light detection unit 307 that receives an optical signal 310 that is out of the optical deflector 305 and outputs an electrical signal that reflects the amount of light. In one example, the optical deflector 305 is composed of a MEMS mirror, and thus the optical deflector array 306 can be composed of a MEMS mirror array. Here, the MEMS mirror includes, for example, a mirror that can swing around two axes, and controls the direction of the reflecting surface of the mirror (for example, the direction of the normal line standing on the reflecting surface) by inputting an electric signal such as a voltage. The resulting MEMS device is intended. However, the optical deflector 305 is not limited to the MEMS mirror, and may be composed of any other element capable of deflecting light.

  The wavelength selective switch 300 further includes a position changing unit 309 that can change the position of the optical deflector array 306 with respect to an optical signal incident on the optical deflector array 306, and a position changing unit 309 based on the detection result by the light detecting unit 307. A control unit 308 for servo control is provided. The position changing unit 309 can be configured by, for example, a stage driven by a motor or the like that movably supports the optical deflector array 306.

  The configuration of the optical deflector array 306 will be described with reference to FIG. As shown in FIG. 8, the optical deflector array 306 has a plurality of, for example, N (N is a natural number) optical deflectors 305-1 to 305-N. In FIG. 8, an optical deflector 305-1 represents the leftmost optical deflector, and an optical deflector 305-N represents the rightmost optical deflector. The optical deflector 305-M (1 ≦ M ≦ N) represents the Mth optical deflector starting from the left side including the optical deflectors 305-1 and 305-N.

  The optical deflectors 305-1 to 305-N are arranged in the demultiplexing direction of the demultiplexer-multiplexer 304. Here, the demultiplexing direction of the demultiplexer / multiplexer 304 means the spreading direction of beams of a plurality of wavelengths demultiplexed by the demultiplexer / multiplexer 304 on the optical deflector array 306. When a mirror or the like exists between the demultiplexer / multiplexer 304 and the optical deflector array 306, the beam spreading directions of the plurality of wavelengths on the optical deflector array 306 are beams of the plurality of wavelengths immediately after demultiplexing. Although not necessarily coincident with the spreading direction, it is referred to as such for convenience.

  The optical deflector array 306 further includes a pair of photodetectors 307-1 and 307-2 arranged along the demultiplexing direction of the demultiplexer-multiplexer 304. The photodetectors 307-1 and 307-2 are arranged on both sides of the entire optical deflectors 305-1 to 305-N along the demultiplexing direction of the demultiplexer-multiplexer 304. The pair of photodetectors 307-1 and 307-2 constitutes the photodetector 307 shown in FIG. In other words, the light detection unit 307 includes a pair of light detectors 307-1 and 307-2.

  The configuration of the control unit 308 will be described with reference to FIG. As shown in FIG. 9, the control unit 308 temporarily stores and updates the electrical signal (voltage value) from the photodetectors 307-1 and 307-2 for each photodetector, thereby changing the value of the electrical signal. LUT which stores the initial value of the voltage value of the photodetectors 307-1 and 307-2, that is, the voltage value (calibration data) in which the center wavelength shift of the filter characteristics has not occurred (Look-up table) 602, a calculation unit 601 that detects the occurrence of the center wavelength shift of the filter characteristics with reference to the LUT 602 with respect to the output of the monitor unit 600, and outputs a control signal for correcting the shift amount; A driver 603 that receives the control signal from the unit 601 and drives the position changing unit 309 is provided.

(Function)
Next, the operation of the wavelength selective switch 300 of the first embodiment will be described.
With reference to FIGS. 7 and 8, the basic operation from the input to the output of the wavelength-multiplexed optical signal in the wavelength selective switch 300 will be described. First, in FIG. 7, the wavelength-multiplexed optical signal is input from the input port 301 and enters the demultiplexer / multiplexer 304 through the optical member 303, where it is diffracted in different angular directions depending on the wavelength, Are split into beams having a wavelength of 1 and reach the optical deflector array 306. As shown in FIG. 8, the optical deflector array 306 includes optical deflectors 305-1 to 305-N respectively corresponding to a plurality of wavelengths of beams, and each of the plurality of wavelengths of beams is independently determined in a predetermined manner. Can be deflected to an angle. Specifically, when the optical deflector 305 is an electrostatic attraction type movable mirror, the movable mirror has a predetermined angle by applying a predetermined voltage. The deflected optical signal passes through an optical path different from the optical path from the input port, and is output again to the output port 302 via the demultiplexer / multiplexer 304 and the optical member 303. Therefore, it is possible to select and output only an optical signal having a wavelength corresponding to the designated mirror among the optical deflectors 305-1 to 305-N. The basic operation in the wavelength selective switch 300 has been described above.

  Here, assuming a case where the center wavelength shift of the filter characteristics occurs due to disturbance such as an environmental change, the correction method of the center wavelength shift of the filter characteristics according to the present embodiment will be described. The correction methods are roughly classified into (1) detection of the center wavelength shift, (2) calculation of the direction and amount of the center wavelength shift, (3) position change (movement) of the optical deflector array 306, and the above three items. . The outline of the correction method will be described below with reference to FIG. When the center wavelength shift of the filter characteristics occurs due to the shift of the installation position of the optical deflector array 306 or the shift of the beam spot, the increase or decrease in the amount of light received by the light detection unit 307 receiving a part of the optical signal. The shift direction and the shift amount are calculated, and the position changing unit 309 is driven so as to cancel the shift amount. Thereby, the installation position of the optical deflector array 306 is changed, and the center wavelength shift of the filter characteristic is corrected.

  Details of the correction method will be described below with reference to FIGS. 8, 9, and 10. FIG.

  First, (1) a method for detecting the center wavelength shift of the filter characteristics will be described.

  As shown in FIG. 10, an optical signal having a wavelength corresponding to the Nth optical deflector 305-N is incident on the Nth optical deflector 305-N to form a beam spot 700. In the state where the center wavelength shift of the filter characteristic does not occur, the center of the beam spot 700 is located at the center of the optical deflector 305-N. The center coordinate 702 of the beam spot 700 at this time is set as a reference 0. Here, it is assumed that a disturbance such as an environmental change occurs and the beam spot 700 moves in the + direction to become the beam spot 701. The center coordinate 703 of the beam spot at this time is set to + x1. A part of the beam spot 701 is separated from the optical deflector 305-N and enters the photodetector 307-2. The photodetector 307-2 receives the light that has been removed, and outputs an electrical signal corresponding to the amount of light. By monitoring the increase / decrease in the electrical signal output from the photodetector 307-2, it is possible to detect the occurrence of a center wavelength shift in the + direction.

  Further, when a shift in the center wavelength in the-direction occurs, the increase and decrease in the electrical signal output from the photodetector 307-1 are monitored based on the same principle to correspond to the first optical deflector 305-1. By detecting the movement in the − direction of the beam spot having the wavelength to be detected, it is possible to detect the occurrence of the center wavelength shift in the − direction.

  This is the method for detecting the center wavelength shift of the filter characteristics.

  Next, (2) a deviation amount calculation method after detection of the center wavelength deviation of the filter characteristics and (3) a method for changing the position of the deviation target will be described.

  FIG. 11 shows an operation flow from detection of the center wavelength shift to correction.

  (Step 801) Correction is started. For example, initialization processing of each unit of the photodetectors 307-1 and 307-2 and the control unit 308 is performed.

  (Step 802) The monitor unit 600 monitors the electrical signals of the photodetectors 307-1 and 307-2.

  (Step 803) The computing unit 601 compares the electrical signals of the photodetectors 307-1 and 307-2 with the calibration data stored in the LUT.

  (Step 804) If the electrical signals of the photodetectors 307-1 and 307-2 match the calibration data, the process proceeds to Step 801 without changing the position of the optical deflector array 306. For example, when the electrical signal of the photodetector 307-2 matches the calibration data, the optical signal of the wavelength corresponding to the Nth optical deflector 305-N forms the beam spot 700 of FIG. It is imagined that On the other hand, if the electrical signals of the photodetectors 307-1 and 307-2 do not match the calibration data, the process proceeds to step 805 in order to change the position of the optical deflector array 306. For example, when the electrical signal of the photodetector 307-2 does not match the calibration data, the optical signal having the wavelength corresponding to the Nth optical deflector 305-N forms the beam spot 701 in FIG. It is imagined that

  (Step 805) In the calculation unit 601, a control signal corresponding to the driving amount of the position changing unit 309 is output to the driver 603 based on the difference amount between the calibration data and the electric signal.

  (Step 806) The driver 603 drives the position changing unit 309 based on the control signal to change the position of the optical deflector array 306. Thereafter, the process proceeds to step 801 (feedback control).

  Through the series of steps 801 to 806, for example, the center of the beam spot formed by the optical signal having the wavelength corresponding to the optical deflectors 305-1 and 305-N is made the center of the optical deflectors 305-1 and 305-N. Maintained. Therefore, the center of the beam spot formed by the optical signal having the wavelength corresponding to the optical deflector 305-M is also maintained at the center of the optical deflector 305-M with respect to the demultiplexing direction. As a result, the center of the filter characteristic of the wavelength selective switch 300 is matched with the ITU-GRID.

  In the present embodiment, since the optical deflector array 306 is moved one-dimensionally, the position changing unit 309 may be configured with a stage that can be moved one-dimensionally.

(effect)
As can be seen from the above description, in the wavelength selective switch 300 of the present embodiment, the optical components such as the optical deflector array 306 are displaced due to disturbances such as environmental changes, and the resulting center wavelength displacement of the filter characteristics occurs. Even in this case, the center wavelength shift of the filter characteristics is quickly corrected.

Second Embodiment
A wavelength selective switch according to a second embodiment of the present invention will be described.
The basic configuration of the wavelength selective switch of the second embodiment is the same as that of the first embodiment, and is thus as shown in FIG. The wavelength selective switch of the second embodiment is different from the wavelength selective switch of the first embodiment in the configuration of the optical deflector array 306 and the function of the control unit 308. In the following, an explanation will be given with an emphasis on the difference. That is, the part which is not touched by the following description is the same as that of 1st Embodiment.

(Constitution)
In the second embodiment, as shown in FIGS. 12 and 13, the optical deflector array 306 includes a plurality of pairs of photodetectors 307 -M- 1 arranged along the demultiplexing direction of the demultiplexer / multiplexer 304. , 307-M-2. The photodetectors 307 -M- 1 and 307 -M- 2 are arranged on both sides of each optical deflector 305 -M along the demultiplexing direction of the demultiplexer-multiplexer 304. These plural pairs of photodetectors 307-M-1 and 307-M-2 constitute the photodetector 307 shown in FIG. In other words, the light detection unit 307 includes a plurality of pairs of light detectors 307-M-1, 307-M-2. As can be seen from FIG. 600 monitors the electrical signals (voltage values) from the photodetectors 307-M-1 and 307-M-2. The monitor unit 600 also has a function of selecting the photodetectors 307-M-1 and 307-M-2 to be monitored. The LUT 602 stores initial values of the voltage values of the photodetectors 307-M-1 and 307-M-2, that is, voltage values (calibration data) in a state in which the center wavelength shift of the filter characteristics has not occurred. Furthermore, the calculation unit 601 detects the occurrence of the center wavelength shift of the filter characteristics with reference to the LUT 602 with respect to the output of the monitor unit 600, and outputs a control signal for correcting the shift amount.

(Function)
The monitor unit 600 selects the photodetectors 307-M-1, 307-M-2 to be monitored, and monitors the electrical signals of the selected photodetectors 307-M-1, 307-M-2. A selection target is a plurality of photodetectors 307-M-1 and 307-M-2 corresponding to a plurality of optical deflectors 305-M on which beams of a plurality of wavelengths included in an input optical signal are incident. . The monitor unit 600 may select, for example, one of the plurality of photodetectors 307-M-1 and 307-M-2 and monitor the electrical signal. Alternatively, some or all of the plurality of photodetectors 307-M-1 and 307-M-2 may be selected, and their electrical signals may be monitored in order. The calculation unit 601 detects and corrects the center wavelength shift of the filter characteristics by performing the same processing as in the first embodiment on the electrical signal monitored by the monitor unit 600.

(effect)
The wavelength selective switch of the second embodiment has the same advantages as the wavelength selective switch of the first embodiment, and also has the following advantages.

  The wavelength selective switch of the first embodiment can detect and correct the center wavelength shift only when an optical signal having a wavelength corresponding to one of the optical deflectors 305-1 and 305-N at both ends is input. . In other words, detection and correction of the center wavelength shift cannot be performed unless an optical signal having a wavelength corresponding to one of the optical deflectors 305-1 and 305-N is input.

  On the other hand, the wavelength selective switch according to the second embodiment is capable of detecting the center wavelength deviation and receiving the optical signal having the wavelength corresponding to any of the optical deflectors 305-1 to 305-N. Modifications can be made. When using the wavelength selective switch, an optical signal having a wavelength corresponding to at least one (actually two or more) of the optical deflectors 305-1 to 305-N is always input. Therefore, in the wavelength selective switch of the second embodiment, During use, detection and correction of the center wavelength shift is always performed.

<Third Embodiment>
A wavelength selective switch according to a third embodiment of the present invention will be described.
Originally, a wavelength selective switch is desired to have a small optical loss. The positional deviation between the beam spot and the optical deflector causes a part of the beam spot to deviate from the optical deflector and cause optical loss. As described above, the positional deviation of the beam spot and the optical deflector in the demultiplexing direction should be corrected from the viewpoint of preventing the center wavelength deviation of the filter characteristics. In addition to this, it is preferable that the vertical displacement between the beam spot and the optical deflector is also corrected in view of reducing the optical loss.

  Based on such a viewpoint, the wavelength selective switch of the third embodiment is configured to be able to correct the positional deviation between the beam spot and the optical deflector not only in the demultiplexing direction but also in the vertical direction.

  The basic configuration of the wavelength selective switch of the third embodiment is the same as that of the first embodiment, and is thus as shown in FIG. The wavelength selective switch of the second embodiment is different from the wavelength selective switch of the first embodiment in the configuration of the optical deflector array 306 and the function of the control unit 308. In the following, an explanation will be given with an emphasis on the difference. That is, the part which is not touched by the following description is the same as that of 1st Embodiment.

(Constitution)
In the third embodiment, as shown in FIGS. 15 and 16, the optical deflector array 306 includes a plurality of pairs arranged along the demultiplexing direction of the demultiplexer / multiplexer 304 as in the second embodiment. Photodetectors 307-M-1 and 307-M-2 are included. The photodetectors 307 -M- 1 and 307 -M- 2 are arranged on both sides of each optical deflector 305 -M along the demultiplexing direction of the demultiplexer-multiplexer 304. Furthermore, the optical deflector array 306 includes a plurality of pairs of photodetectors 307 -M-3 and 307 -M-4 arranged along the demultiplexing direction of the demultiplexer / multiplexer 304. The photodetectors 307-M-3 and 307-M-4 are arranged on both sides of each optical deflector 305-M along the vertical direction of the demultiplexing direction of the demultiplexer-multiplexer 304. The plurality of pairs of photodetectors 307-M-1, 307-M-2, 307-M-3, and 307-M-4 constitute the photodetector 307 shown in FIG. In other words, the light detection unit 307 includes a plurality of pairs of light detectors 307-M-1, 307-M-2, 307-M-3, and 307-M-4.

  In the control unit 308 of the third embodiment, as can be seen from FIG. 17, the monitor unit 600 includes the detectors 307 -M-1, 307 -M-2, 307 -M-3, and 307 -M-4. Monitor electrical signals (voltage values). The monitor unit 600 has a selection function of the photodetectors 307-M-1, 307-M-2, 307-M-3, and 307-M-4 to be monitored. The LUT 602 is an initial value of the voltage values of the photodetectors 307-M-1, 307-M-2, 307-M-3, and 307-M-4, that is, a voltage in a state where the center wavelength shift of the filter characteristics has not occurred. The value (calibration data) is stored. Furthermore, the calculation unit 601 detects the occurrence of the center wavelength shift of the filter characteristics with reference to the LUT 602 with respect to the output of the monitor unit 600, and outputs a control signal for correcting the shift amount.

(Function)
The correction of the center wavelength shift of the filter characteristics in the third embodiment will be described with reference to FIG.

  (Step 901) Correction is started. For example, initialization processing of each unit of the photodetectors 307-M-1, 307-M-2, 307-M-3, 307-M-4 and the control unit 308 is performed.

  (Step 902) In the monitor unit 600, the photodetectors 307-M-1, 307-M-2, 307-M-3, and 307-M-4 to be monitored are selected. The selection method is the same as in the second embodiment. Further, the electrical signals of the photodetectors 307-M-3 and 307-M-4 are monitored.

  (Step 903) The computing unit 601 compares the electrical signals of the photodetectors 307-M-3 and 307-M-4 with the calibration data stored in the LUT.

  (Step 904) If the electrical signals of the photodetectors 307-M-3 and 307-M-4 match the calibration data, the process proceeds to Step 907 without changing the position of the optical deflector array 306. . In this case, it is assumed that the optical signal having the wavelength corresponding to the optical deflector 305-M forms a beam spot at the center of the optical deflector 305-M in the vertical direction. On the other hand, if the electrical signals of the photodetectors 307-M-3 and 307-M-4 do not match the calibration data, the process proceeds to step 905 to change the vertical position of the optical deflector array 306. To do. In this case, it is assumed that the optical signal having the wavelength corresponding to the optical deflector 305-M forms a beam spot at a position shifted from the center of the optical deflector 305-M in the vertical direction.

  (Step 905) The calculation unit 601 outputs a control signal corresponding to the driving amount of the position changing unit 309 to the driver 603 based on the difference amount between the electrical signal and the calibration data.

  (Step 906) The driver 603 drives the position changing unit 309 based on the control signal to change the vertical position of the optical deflector array 306. Thereafter, the process proceeds to step 907.

  (Step 907) The monitor unit 600 monitors the electrical signals of the photodetectors 307-M-1 and 307-M-2.

  (Step 908) The arithmetic unit 601 compares the electrical signals of the photodetectors 307-M-1 and 307-M-2 with the calibration data stored in the LUT.

  (Step 909) If the electrical signals of the photodetectors 307-M-1 and 307-M-2 match the calibration data, the process proceeds to step 901 without changing the position of the optical deflector array 306. . In this case, it is assumed that the optical signal having the wavelength corresponding to the optical deflector 305-M forms a beam spot at the center of the optical deflector 305-M in the demultiplexing direction. On the other hand, if the electrical signals of the photodetectors 307-M-1 and 307-M-2 and the calibration data do not match, go to Step 910 to change the position of the optical deflector array 306 in the demultiplexing direction. Transition. In this case, it is assumed that the optical signal having the wavelength corresponding to the optical deflector 305-M forms a beam spot at a position shifted from the center of the optical deflector 305-M in the demultiplexing direction.

  (Step 910) The calculation unit 601 outputs a control signal corresponding to the driving amount of the position changing unit 309 to the driver 603 based on the difference amount between the electrical signal and the calibration data.

  (Step 911) The driver 603 drives the position changing unit 309 based on the control signal to change the position of the optical deflector array 306 in the demultiplexing direction. Thereafter, the process proceeds to step 901.

  Through a series of these steps 901 to 911, the center of the beam spot formed by the optical signal having the wavelength corresponding to the selected optical deflector 305-M is the optical deflector 305- in both the demultiplexing direction and the vertical direction. Maintained in the center of M. Accordingly, the centers of the beam spots formed by the optical signals having the wavelengths corresponding to all the optical deflectors 305-1 to 305-N are the optical deflectors 305-1 to 305 in both the demultiplexing direction and the vertical direction, respectively. Maintained at the center of -N.

  In the processing by the operation flow of FIG. 18, the detection and correction of the demultiplexing direction are performed after the detection and correction in the vertical direction, but this is merely an example, and their order may be reversed.

  In this embodiment, since the optical deflector array 306 is moved two-dimensionally, the position changing unit 309 may be configured by a so-called XY stage that can move two-dimensionally.

(effect)
The wavelength selective switch of the third embodiment has the same advantages as the wavelength selective switch of the second embodiment, and also has the following advantages.

  Since the positional deviation in the vertical direction in addition to the positional deviation in the demultiplexing direction of the beam spot and the optical deflector is corrected, the optical loss of the wavelength selective switch is reduced.

  The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to these embodiments, and various modifications and changes can be made without departing from the scope of the present invention. Also good. The various modifications and changes described here include an implementation in which the above-described embodiments are appropriately combined.

DESCRIPTION OF SYMBOLS 300 ... Wavelength selection switch, 301 ... Input port, 302 ... Output port, 303 ... Optical member, 304 ... Demultiplexer / multiplexer, 305, 305-1 to 305-N ... Optical deflector, 306 ... Optical deflector array, 307: Photodetector, 307-1, 307-2, 307-M-1, 307-M-2, 307-M-3, 307-M-4 ... Photodetector, 308: Controller, 309 ... Position Change unit, 310 ... deviated optical signal, 600 ... monitor unit, 601 ... calculation unit, 603 ... driver, 700, 701 ... beam spot, 702, 703 ... center coordinates.

Claims (5)

An input port for receiving wavelength-multiplexed optical signals;
An output port from which the optical signal is output;
A demultiplexer / multiplexer for demultiplexing and multiplexing the optical signal;
An optical deflector array capable of deflecting the optical signal for each wavelength;
An optical member that couples the input port and the output port via the branching multiplexer and the optical deflector;
The optical deflector array receives a plurality of optical deflectors arranged in the demultiplexing direction of the demultiplexer / multiplexer, and an optical signal that deviates from the optical deflector, and outputs an electric signal reflecting the amount of light. Having a light detection unit, and
A position changing unit capable of changing the position of the optical deflector array;
A wavelength selective switch having a control unit that servo-controls the position changing unit based on a detection result by the light detection unit.   The light detection unit includes a pair of photodetectors arranged along the demultiplexing direction, and the pair of photodetectors includes a whole of the plurality of optical deflectors along the demultiplexing direction. The wavelength selective switch according to claim 1, which is disposed on both sides.   The light detection unit includes a plurality of pairs of light detectors arranged along the demultiplexing direction, and each pair of light detectors is provided on both sides of each light deflector along the demultiplexing direction. The wavelength selective switch according to claim 1, which is arranged.   The photodetector further includes a plurality of pairs of second photodetectors arranged along the demultiplexing direction, and each pair of second photodetectors extends along a direction perpendicular to the demultiplexing direction. 4. The wavelength selective switch according to claim 3, wherein the wavelength selective switch is disposed on both sides of each of the optical deflectors.   5. The wavelength selective switch according to claim 1, wherein the position changing unit includes a stage that supports the optical deflector array so as to be movable at least in the demultiplexing direction. 6.

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