Optical signal processing device and control method thereof

Abstract

The present invention solves the problem in that because the wavelength spectrum changes in an analog manner when the settings in a plurality of phase shifters are being changed, the spectrum significantly deviates from a desired wavelength spectrum. An optical signal processing device according to the present invention divides the amount between a present phase modification amount and a target phase modification amount into M segments, acquires M+1 phase modification amounts including the present phase modification amount and the target phase modification amount, and then gradually changes the settings for the phase modification amounts to be applied by the respective phase shifters.

Description

Technical Field

[0001] The present invention relates to an optical signal processing device, and more particularly to a technology for controlling the amount of phase modulation of an optical signal propagating through an optical waveguide.

Background Art

[0002] The wavelength division multiplexing (WDM) technology used in optical communication networks is regarded as an important means for realizing large-capacity optical communication.

[0003] For example, in order to apply the WDM technology to transmission over a distance of 100 km or more, it is necessary to arrange optical amplifiers at regular intervals in the transmission fiber. Since the wavelength dependence of its gain spectrum greatly affects the optical signal-to-noise ratio (OSNR), it is necessary to flatten the gain spectrum. As this gain equalizer, a gain equalizer composed of a silica-based glass waveguide disclosed in Non-Patent Document 1 has been proposed. Non-Patent Document 2 also discloses a gain equalizer having a configuration called a lattice-type optical circuit.

[0004] This lattice-type optical circuit is composed of N directional couplers and N - 1 arm waveguides formed by two waveguides sandwiched between them. Further, by applying heat to at least one of the two waveguides constituting the arm waveguide, it operates as a phase shifter utilizing the refractive index change due to the thermo-optical effect, and controls the phase of the light propagating therein. By this control, the phase difference between the optical signals propagating through the two waveguides constituting the arm waveguide can be adjusted, the interference state in the subsequent directional coupler can be adjusted, and the transmission spectrum with respect to wavelength can be controlled.

[0005] As described above, optical signal processing devices, which consist of an optical waveguide and multiple phase shifters that impart a phase shift to the optical signal propagating through the waveguide, are widely used in optical communication networks. One example is a lattice-type optical circuit, which consists of N directional couplers, N-1 arm waveguides consisting of two waveguides sandwiched between them, and up to 2(N-1) phase shifters loaded on at least one of the two waveguides constituting the arm waveguides. In the i-th arm waveguide of the lattice-type optical circuit, the phase difference Θi that occurs between the upper arm waveguide and the lower arm waveguide is expressed by equation (1).

[0006]

number

[0007] Here, λ is the wavelength of light, n eff ΔLi is the effective refractive index of the optical waveguide, ΔLi is the difference in length between the upper and lower arm waveguides in the i-th arm waveguide, and φi is the phase difference applied between the arms by the phase shifter in the i-th arm waveguide. By individually controlling the amount of phase modulation applied by multiple phase shifters, the phase difference φi in each arm waveguide is controlled, and the final output wavelength spectrum is controlled. Since the phase shifter settings can be freely changed even while an optical signal is being transmitted, the wavelength spectrum can be sequentially and arbitrarily changed according to the optical signal transmission conditions. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] K. Suzuki, T. Kitoh, S. Suzuki, Y. Inoue, Y. Hbbino, T. Shibata, A. Mori, and M. Shimizu. 2002), paper IThG2. [Non-Patent Document 2] TR Schlipf, MW Street, J. Pandavenes, R. McBride, and DRS Cumming, “Design and Analysis of a Control System for an Optical Delay-Line Circuit Used as Reconfigurable Gain Equalizer,” Journal of Lightwave Technology, 2003, Vol. 21, Issue 9, pp. 1944. [Overview of the project] [Problems that the invention aims to solve]

[0009] However, when changing the wavelength spectrum of an optical signal processing device, the waveform continuously changes during the setting process at multiple phase shifters. Therefore, if the amount of phase modulation to be set is large, the wavelength spectrum may deviate significantly from the desired wavelength spectrum. Furthermore, if the deviation of the optical characteristics from the desired wavelength spectrum is large, there is a risk that the transmitted optical signal may be interrupted.

[0010] The present invention aims to provide an optical signal processing device that can obtain a desired wavelength spectrum even when the phase modulation amount of a phase shifter is changed during optical signal transmission. [Means for solving the problem]

[0011] The present invention provides a control method for an optical signal processing apparatus, comprising an optical waveguide formed on a substrate and N phase shifters that apply a phase shift to an optical signal propagating through the optical waveguide, characterized in that the method includes: a first step of dividing the space between the currently applied phase shift amount and the target phase shift amount into M divisions and obtaining (M+1) phase shift amounts, including the phase shift amounts before and after the change, for each of the N phase shifters; and a second step of changing the phase shift amount applied to each of the N phase shifters from the first to the Nth phase shifter, changing the phase shift amount from the kth phase shift amount to the (k+1)th phase shift amount among the (M+1) phase shift amounts, and repeating the second step M times from k=1 to k=M. [Effects of the Invention]

[0012] With the above configuration, it is possible to obtain a desired wavelength spectrum in the optical signal processing device even if the phase modulation amount of the phase shifter is changed during optical signal transmission. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a top view of the optical signal processing device of the present invention. [Figure 2] Figure 2 is a graph showing the wavelength spectrum of the transmittance of a lattice-type optical circuit. [Figure 3] Figure 3 is a flowchart showing a process according to the first embodiment of the present invention, in which the current phase modulation amount and the target phase modulation amount are linearly divided to determine the number of divisions M. [Figure 4] Figure 4 shows a lookup table according to a modified example of the first embodiment of the present invention. [Figure 5] FIG. 5 is a diagram showing the amount of phase modulation in the phase shifter in each step according to the first embodiment. [Figure 6] FIG. 6 is a flowchart showing a process of determining the number of divisions M when using the look-up table shown in FIG. 4. [Figure 7] FIG. 7(a) is a diagram showing an example of the amount of phase modulation added to each phase shifter for each spectral slope according to the second embodiment of the present invention, and FIG. 7(b) is a diagram showing an example of a graph after dividing the amount of phase modulation. [Figure 8] FIG. 8 is a diagram showing a look-up table that defines the amount of phase modulation for each spectral slope according to the second embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

[0014] (Structure of optical signal processing device) FIG. 1 is a diagram schematically showing an optical signal processing device according to an embodiment of the present invention. The optical signal processing device of this embodiment shows the case of a lattice-type optical circuit as an example of the form of an optical waveguide, but the form of the optical waveguide is not limited to this. The optical signal processing device of this embodiment includes a lattice-type optical circuit 11 and a control unit 10 that controls the amount of phase modulation by a phase shifter having a phase modulation function in this optical circuit. The control unit may also execute a division process of the amount of phase modulation described later in FIGS. 3, 6, etc.

[0015] The control unit 10 has a CPU and a memory that stores programs executed by the CPU, such as control of an optical signal processing device and division processing of a phase modulation amount, which will be described later, and executes control processing of the phase modulation amount by a phase shifter described below. The lattice optical circuit 11 includes an input waveguide 111, optical directional couplers 113-1 to 113-N, arm waveguides 114-1 to 114-(N-1), and an output waveguide 112. The arm waveguides 114-1 to 114-(N-1) are each composed of two waveguides, and phase shifters 115-1 to 115-(N-1) and 116-1 to 116-(N-1) are respectively loaded on both waveguides. Note that in order to execute the phase modulation processing of the present invention, it is clear from the following description that it is sufficient if a phase shifter is loaded on at least one of the two waveguides.

[0016] The signal light input from the input waveguide 111 passes through the optical directional couplers 113-1 to 113-N and the arm waveguides 114-1 to 114-(N-1) alternately in the order shown in the figure, and is output from the output waveguide 112.

[0017] (Phase shifter) The phase shifters 115-1 to 115-(N-1) and 116-1 to 116-(N-1) respectively arranged in the arm waveguides 114-1 to 114-(N-1) control the phase of the optical signal passing through the corresponding waveguide. As the phase shifter, any principle may be used as long as it can control the phase of the passed optical signal. For example, a thermo-optic phase shifter using heat generated by a heater and the thermo-optic effect can be mentioned. In the case of a thermo-optic phase shifter, the heat generated by the amount of current applied to the heater is controlled, and the phase modulation amount is controlled by the refractive index change of the waveguide associated therewith.

[0018] (Control of optical signal processing device) The following describes the control of an optical signal processing device according to one embodiment of the present invention. For the sake of simplicity in illustration and explanation, the case in which the lattice-type optical circuit is composed of six directional couplers and five pairs of arm waveguides (N=6) will be described. Similarly, for the sake of simplicity in illustration and explanation, it will be assumed that the phase shifters 115-1 to 115-5 are arranged in only one of the two arm waveguides 114-1 to 114-5.

[0019] Figure 2 is a graph showing the wavelength spectrum of the transmittance of the optical signal in the lattice-type optical circuit 11, with the vertical axis representing transmittance and the horizontal axis representing the wavelength of light. In Figure 2, waveform A is the waveform currently set as the transmission spectrum in the lattice-type optical circuit 11, and as an example, it is a waveform that shows a nearly linear spectrum with a slope of approximately -0.2 dB / nm. Waveform D is the target transmittance spectrum waveform controlled by the variable phase amount, and as an example, it is a waveform with a nearly linear spectrum with a slope of approximately -0.1 dB / nm. The current phase modulation amounts applied by phase shifters 115-1 to 115-5 are φ01, φ02, φ03, φ04, and φ05, respectively. With the above settings, the transmission spectrum of the lattice-type optical circuit 11 is changed from the currently set waveform A to the target set waveform D by changing the phase modulation amount applied by each phase shifter. Here, the target phase modulation amounts to be applied by phase shifters 115-1 to 115-5 to obtain the target waveform D are denoted as φM1, φM2, φM3, φM4, and φM5, respectively.

[0020] The transmitted spectrum during waveform modification must remain within the acceptable range for the optical communication network. In the example shown in Figure 2, this range is between waveform F (upper limit) and waveform E (lower limit). This corresponds to a range of ±0.3 dB for both waveform A and waveform D.

[0021] When changing the waveform, if the phase modulation amount applied by phase shifters 115-1 to 115-5 is directly changed from the current phase modulation amounts φ01, φ02, φ03, φ04, φ05 to the target phase modulation amounts φM1, φM2, φM3, φM4, φM5, as mentioned above, the waveform will continue to change continuously during the change by the five phase shifters. Therefore, at some point during the setting change, the transmission spectrum of the lattice-type optical circuit may exceed the acceptable range. For example, waveform B shown in Figure 2 is an example of a transmission spectrum during the process of changing the phase modulation amount applied by phase shifters 115-1 to 115-5. At a wavelength of approximately 1565 nm, the transmission spectrum changes by approximately 1.8 dB beyond the acceptable range.

[0022] Therefore, in the control of the optical signal processing device according to this embodiment, first, the current phase modulation amount and the target phase modulation amount are each divided into M segments, and M+1 phase modulation amounts including the current phase modulation amount and the target phase modulation amount are calculated as follows.

[0023] Current phase modulation amounts: φ01, φ02, φ03, φ04, φ05 Phase modulation amount for the first segment after splitting: φ11, φ12, φ13, φ14, φ15 Phase modulation amount for the second segment after splitting: φ21, φ22, φ23, φ24, φ25 ... M-1st phase modulation amount after division: φ(M-1)1, φ(M-1)2, φ(M-1)3, φ(M-1)4, φ(M-1)5 Target phase modulation amounts: φM1, φM2, φM3, φM4, φM5

[0024] Subsequently, when changing the waveform, the amount of phase modulation applied by each of the phase shifters 115-1 to 115-5 is changed from the k-th phase modulation amount to the (k+1)-th phase modulation amount out of the M+1 phase modulation amounts, and this is done for each of the phase shifters 115-1 to 115-5 one by one. This step is repeated M times from k=1 to k=M, gradually changing the amount of phase modulation applied by the phase shifters 115-1 to 115-5 from the current phase modulation amount until it reaches the target phase modulation amount. The flow of the phase modulation amount change process is as follows.

[0025] Step 1: φ01→φ11, φ02→φ12, φ03→φ13, φ04→φ14, φ05→φ15 Step 2: φ11→φ21, φ12→φ22, φ13→φ23, φ14→φ24, φ15→φ25 Step 3: φ21→φ31, φ22→φ32, φ23→φ33, φ24→φ34, φ25→φ35 ... Step M-1: φ(M-2)1 → φ(M-1)1, φ(M-2)2 → φ(M-1)2, φ(M-2)3 → φ(M-1)3, φ(M-2)4 → φ(M-1)4, φ(M-2)5 → φ(M-1)5 Step M: φ(M-1)1→φM1, φ(M-1)2→φM2, φ(M-1)3→φM3, φ(M-1)4→φM4, φ(M-1)5→φM5

[0026] As described above, by changing the setting of the phase modulation amount applied by phase shifters 115-1 to 115-5 to a divided minute modulation amount as described later as a division process, even when the waveform changes continuously, the change in the transmission spectrum of the lattice-type optical circuit can be kept within an acceptable range, as shown by waveform C in Figure 2.

[0027] As described above, the control of the optical signal processing device according to this embodiment allows the change in the characteristics of the optical signal processing device to be kept within an acceptable range, regardless of any change in the phase shifter setting, and the desired signal processing characteristics can be achieved without affecting the transmission characteristics in the optical communication network. Here, transmission characteristics refer to characteristics that represent the transmission quality of the optical signal, such as the bit error rate.

[0028] In this embodiment, the case where the phase shifter 115-1 to 115-5 is adjusted one by one in each step is shown, but it may be adjusted simultaneously within the same step, or multiple shifters may be adjusted at once. The same applies when N is any other natural number. The phase modulation amount may be set in the optical signal processing device, by external software, or by hardware.

[0029] (Partitioning process) In the control of the optical signal processing device according to this embodiment, the division method for dividing the current phase modulation amount and the target phase modulation amount into M divisions is either to divide the current phase modulation amount and the target phase modulation amount linearly, or to divide it according to a pre-prepared lookup table of phase modulation amounts. The number of divisions M is determined according to the difference between the current phase modulation amount and the target phase modulation amount and the allowable value of the change in optical characteristics passing through the optical signal processing device. When the allowable value of the change in optical characteristics passing through the optical signal processing device is Q, the optical characteristics for any phase modulation amount setting φmn (m, n are integers; 1 ≤ m ≤ M, 1 ≤ n ≤ N-1) between the initial waveform and the target waveform are theoretically calculated in advance, and the number of divisions M is determined so that the optical characteristics fall within the range ±Q between the initial characteristics and the target characteristics.

[0030] Figure 3 is a flowchart showing the process for determining the number of divisions of the phase modulation amount according to the first embodiment of the present invention.

[0031] First, the current phase modulation amounts (φ01, φ02, ..., φ05) and target phase modulation amounts (φM1, φM2, ..., φM5) are obtained (S301). Also, the number of divisions M is set to the initial value of the number of divisions (1 in this example) (S302).

[0032] Next, each phase modulation amount φmn3) is determined by linear interpolation expressed by the equation φmn = φ0n + mΔφ (S303), and theoretical calculations of the wavelength spectrum for each phase modulation amount φmn are performed (S304).

[0033] Next, it is determined whether the calculated wavelength spectrum is within the acceptable range (S305). If it is not within the acceptable range, the value of the division number is incremented (in this example, +1) (S307), and the process in steps S303 and S304 is repeated. If it is determined that the calculated wavelength spectrum is within the acceptable range, the division number M at that time is set as the number of divisions to be calculated (S306), and this process is terminated. Note that although the initial value of the division number is set to 1, other values ​​are also acceptable, and the value to be incremented is also an integer of 2 or more.

[0034] The transmission spectrum in step S304 of the above division process can be calculated as follows, for example. For example, consider the case where the optical waveguide constituting the optical signal processing device is a lattice-type optical circuit, and the transmission spectrum of the lattice-type optical circuit can be approximated linearly with respect to wavelength. The transmission spectrum of the lattice-type optical circuit can be theoretically calculated by calculating the electric field after transmission for each path, which is equal to the combination of arm waveguides that pass through each stage, and then summing up the electric fields for all paths. Through this theoretical calculation, after dividing the current phase modulation amount and the target phase modulation amount into M divisions, all possible transmission spectra that the lattice filter-type optical circuit can take in each of the aforementioned steps can be calculated. By performing theoretical calculations for multiple division numbers M, it is possible to determine the number of divisions M required to keep the change in the transmission spectrum of the lattice-type optical circuit within an acceptable range.

[0035] Furthermore, while the above example determines the amount of each phase modulation by linear interpolation, a pre-prepared lookup table may also be used.

[0036] Figure 4 shows an example of a lookup table. Similar to the example above, in the example of changing waveform A (before change) to waveform D (after change) in Figure 2, four waveforms are assumed for the intermediate waveform (waveform C), and the lookup table records the phase modulation amounts φ1_1, φ1_2, ... φ1_5, φ2_1, φ2_2, ... of each phase shifter corresponding to waveform A (=waveform 1), the intermediate waveforms (=waveforms 2-5), and waveform D (=waveform 6) as the contents of the table.

[0037] Figure 5 shows the phase modulation amount φn_k determined by the phase shifter k using the lookup table shown in Figure 4, compared to an example using linear interpolation. When dividing and determining each phase modulation amount from the current waveform to the target waveform, the phase modulation amounts corresponding to waveforms 2, 3, 4, and 5 are determined so that the steps (change times) of change from waveform 1 to waveform 6 are equally spaced. Note that when further dividing between waveforms, linear interpolation or other methods may be used.

[0038] Figure 6 is a flowchart showing the process for determining the number of divisions M when using a lookup table. The difference from the division process shown in Figure 3 is the phase modulation amount determination process in step S603. That is, in this example, a lookup table shown in Figure 5 is created for M determined in step S607, and then the phase modulation amount for each division is determined by referring to the lookup table created in step S603.

[0039] Note that the lookup table shown here represents a case with 6 records, from waveform 1 (=before change) to waveform 6 (=after change), but the number of records is not limited to 6. Also, the waveform before change does not need to be the first record, and the waveform after change does not need to be the last record.

[0040] Next, the control of the optical signal processing apparatus according to the second embodiment of the present invention will be described. In the second embodiment, the amount of phase modulation applied by each phase shifter is determined so that the continuous change in the optical characteristics of the optical signal processing apparatus is quantized and changed (changed to a minute (M division)). Then, in accordance with the continuous change in the optical characteristics of the optical signal processing apparatus, the amount of phase modulation applied by each phase shifter is also changed by quantizing a continuous change within a certain phase range.

[0041] As an example, consider a case where the optical signal processing device is a lattice-type optical circuit as shown in Figure 1, and is controlled so that its transmission spectrum approximates the wavelength linearly. That is, consider a case where the optical signal processing device is controlled as a tilt equalizer, i.e., each phase shifter of the optical signal processing device is controlled so that the wavelength spectrum of the transmittance of the optical signal processing device has a linear shape with respect to the wavelength. In this case, in the second embodiment, the optical signal processing device is controlled so that the slope (dB / nm) of the transmission spectrum of the tilt equalizer changes continuously. At this time, the amount of phase modulation applied by each phase shifter is also changed continuously in accordance with the continuous change in the spectral slope of the tilt equalizer, for example, within the range of -π to +π.

[0042] Figure 7(a) shows the amount of phase modulation applied by each phase shifter for each spectral slope (which indicates the shape of the waveform).

[0043] As shown in Figure 7(a), the amount of phase modulation can be approximated by a function that is continuous with respect to the slope of the spectrum. This function can be obtained by theoretical calculation of the transmission spectrum of a lattice-type optical circuit or by actually evaluating the transmission spectrum of a lattice-type optical circuit.

[0044] In this embodiment as well, the control for changing the optical characteristics of the optical signal processing device from the current setting to the target setting is the same as in the first embodiment: the current phase modulation amount and the target phase modulation amount are each divided into M segments, and M+1 phase modulation amounts including the current phase modulation amount and the target modulation amount are calculated. The phase modulation amount applied to each of the phase shifters 115-1 to 115-5 is changed from the k-th phase modulation amount to the (k+1)-th phase modulation amount out of the M+1 phase modulation amounts, and this is done for each of the phase shifters 115-1 to 115-5. This step is repeated M times from k=1 to k=M, so that the phase modulation amount applied to the phase shifters 115-1 to 115-5 is gradually changed from the current setting until it reaches the target setting. As for the division process when dividing the current phase modulation amount and the target phase modulation amount into M segments, the phase modulation amount is divided along the graph line between the plot of the current phase modulation amount and the plot of the target phase modulation amount, as shown in Figure 7(a) in the relationship of phase modulation amounts for each optical characteristic. The process for determining the number of divisions M is the same as in the first embodiment.

[0045] Figure 7(b) shows the amount of phase modulation added by each phase shifter for each slope of the spectrum after the phase modulation amount has been divided. When determining the correspondence after division shown in Figure 7(b), adjacent plots in Figure 7(a) may be connected by a linear line or smoothly by a curve.

[0046] For example, consider a case where the optical waveguide constituting the optical signal processing device is a lattice-type optical circuit, and the lattice-type optical circuit operates as a tilt equalizer. Assume that the allowable value for the change in the transmission spectrum of the optical signal processing device is 0.3 dB. Currently, the slope of the transmission spectrum is -0.2 dB / nm, and the slope of the target transmission spectrum is -0.1 dB / nm. In this case, in the graph of phase modulation amounts for each spectral slope shown in Figure 7, the phase modulation amount is divided into 20 segments at intervals of 0.005 dB / nm on the graph line between the plot of the phase modulation amount at -0.2 dB / nm and the plot of the phase modulation amount at -0.1 dB / nm. At this time, as shown in Figure 8, by referring to a lookup table that defines the phase modulation amount for each spectral slope, and dividing the range from a phase modulation amount of -0.2 dB / nm to a phase modulation amount of -0.1 dB / nm into 20 parts, it can be theoretically determined in advance that the transmission spectrum that can be obtained after one of the aforementioned steps will fall within the range between the straight line obtained by subtracting 0.3 dB from the waveform with a slope of -0.2 dB / nm and the straight line obtained by adding 0.3 dB to the waveform with a slope of -0.1 dB / nm. In other words, the initial waveform can be changed to the target waveform without adversely affecting the transmission characteristics. [Explanation of Symbols]

[0047] 10 Control Unit 11 Lattice-type optical circuit 111 Input Waveguide 112 Output waveguide 113-1~113-N Optical directional coupler 114-1~114-(N-1) Arm Waveguide 115-1~115-(N-1), 116-1~116-(N-1) Phase Shifter

Claims

1. An optical signal processing device comprising an optical waveguide formed on a substrate and N phase shifters that apply a phase shift to an optical signal propagating through the optical waveguide, The first step involves dividing the currently applied phase shift amount and the target phase shift amount into M divisions, and obtaining (M+1) phase shift amounts, including the phase shift amounts before and after the change, for each of the N phase shifters. The second step includes changing the phase shift amount applied to each of the N phase shifters from the kth phase shift amount to the (k+1)th phase shift amount among the (M+1) phase shift amounts, from the first phase shifter to the Nth phase shifter, The above second step is repeated M times from k=1 to k=M. An optical signal processing device configured to perform a process, wherein the phase shift amount in each of the second step, which is repeated M times, is set such that the time intervals between changes in the waveform due to each shift amount are equal.

2. The number of divisions M is determined by the difference between the currently set optical characteristics and the target set optical characteristics. Given a tolerance Q for the change in optical characteristics as the optical signal processing device passes through it, the number of steps M is determined such that the optical characteristics that can be obtained after one second step are within the range ±Q between the currently set optical characteristics and the target set optical characteristics. The optical signal processing apparatus according to feature 1.

3. The control method for the optical signal processing device involves quantizing and changing the continuous change in the optical properties of the optical signal processing device. The optical signal processing apparatus according to claim 1 or 2.

4. The control method for the optical signal processing device is characterized by quantizing and changing the continuous change in the optical properties of the optical signal processing device. The amount of phase shift applied to each of the N phase shifters changes by quantizing a continuous change within a certain phase range, in accordance with the continuous change in the optical properties of the optical signal processing device. The optical signal processing apparatus according to claim 1 or 2.

5. The optical signal processing device is a gain equalizer, and the phase shift amount is determined such that the gain equalization spectrum of the gain equalizer changes linearly with respect to the optical signal wavelength. The optical signal processing apparatus according to claim 1 or 2.

6. The optical signal processing device has at least one input port and at least one output port. The aforementioned optical signal processing device has three or more 2-input 2-output photomultiplier and current splitting circuits, Three or more of the aforementioned two-input, two-output photomultiplier and shunt circuits are connected by a connecting optical waveguide consisting of two optical waveguides sandwiched between the two-input, two-output photomultiplier and shunt circuits. One or more of the two optical waveguides constituting the connecting optical waveguide have a driven element that includes a phase shifter that applies a phase shift to the input optical signal. The optical signal processing apparatus according to claim 1 or 2, characterized by the above.

7. The aforementioned phase shifter is constructed by using the thermo-optic effect and heating the optical waveguide. The optical signal processing apparatus according to claim 1 or 2.

8. A control method for an optical signal processing device comprising an optical waveguide formed on a substrate and N phase shifters that apply a phase shift to an optical signal propagating through the optical waveguide, The first step involves dividing the currently applied phase shift amount and the target phase shift amount into M divisions, and obtaining (M+1) phase shift amounts, including the phase shift amounts before and after the change, for each of the N phase shifters. The second step includes changing the phase shift amount applied to each of the N phase shifters from the kth phase shift amount to the (k+1)th phase shift amount among the (M+1) phase shift amounts, from the first phase shifter to the Nth phase shifter, The above second step is repeated M times from k=1 to k=M. A control method for an optical signal processing device, characterized by executing a process and setting the phase shift amount in each of the second step, which is repeated M times, such that the change time of the waveform change due to each shift amount is at equal intervals.

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