JP4026601B2 - Optical signal processing apparatus and semiconductor intermodulation element control method - Google Patents

Description

  The present invention relates to an optical signal processing apparatus, and more specifically to an optical signal processing apparatus that causes two lights to interact using a semiconductor optical intermodulation element such as a semiconductor optical amplifier (SOA).

  Semiconductor elements generally have a great sensitivity to light. In particular, when light having energy near or higher than the band gap is input, a large interaction with internal carriers (electron / hole pairs) occurs. Semiconductor optical intermodulation elements utilizing such interaction between light and carriers have been widely known in the past, and examples include a semiconductor optical amplifier (SOA) and an electroabsorption optical modulator (EAM).

  For example, in a state where a direct current drive current is applied to the SOA and a gain G is provided for the probe wavelength λp, a pulse-modulated signal light having a signal wavelength λs and a probe having a CW (Continuous wave) probe wavelength λp are applied to the SOA. Light is incident together. The wavelengths λs and λp are both in the SOA absorption wavelength band.

  Within the SOA, carriers are consumed by the signal light having the wavelength λs, and as a result, the gain with respect to the probe light decreases. This phenomenon is called mutual gain modulation (XGM). By utilizing this phenomenon, it is possible to invert the intensity pattern of the pulse signal light having the signal wavelength λs and transfer it to the probe light. Only the component of the probe wavelength λp needs to be extracted from the SOA output light by the optical bandpass filter. Thereby, although the intensity pattern is inverted, the wavelength of the optical carrier carrying the signal can be converted from λs to λp.

  Even if EAM is used instead of SOA, a similar phenomenon is induced and wavelength conversion becomes possible. A reverse bias DC voltage is applied to the pn junction of the EAM. In this state, the signal wavelength λs is set in the vicinity of the EAM absorption band, and the probe wavelength λp is set to a wavelength that is absorbed by the EAM in the reverse bias state.

  When the pulse signal light having the signal wavelength λs and the probe light having the probe wavelength λp are simultaneously incident on the EAM, the EAM absorbs the pulse signal light having the signal wavelength λs, thereby generating a carrier inside the EAM. The generated carriers weaken the internal electric field of the EAM. As a result, the amount of absorption with respect to the probe light is reduced. This phenomenon is called cross absorption modulation (XAM). As a result, the probe light output from the EAM has an intensity pattern similar to that of the pulse signal light having the signal wavelength λs. By extracting the component of the probe wavelength λp from the EAM output light, the signal light of the probe wavelength λp having the same intensity pattern as the pulse signal light of the signal wavelength λs can be extracted. That is, the wavelength of the optical carrier carrying the signal can be converted from λs to λp.

  In both the SOA and EAM, the carrier amount inside the element varies depending on the signal light, so the optical path length with respect to the probe light varies in phase order other than XGM or XAM. Such a phase modulation effect is called cross phase modulation (XPM). Many interferometer type optical switches using the XPM have been proposed.

  For example, an optical switch in which an SOA is incorporated in both arms of a Mach-Zehnder interferometer (MZI) is known. CW probe light is input to both arms, that is, both SOAs, and pulse signal light is supplied to only one arm, that is, only one SOA. Then, the component of the probe wavelength λp is extracted from the combined light of the output lights of both arms, that is, the output light of the MZI, by the optical bandpass filter.

  Assume that the phase difference between both arms is adjusted so that the probe light output from both arms interferes with the destructive and does not appear in the steady state where no pulse signal light is input. . In this state, in the SOA to which the pulse signal light is input, if the XPM amount with respect to the probe light due to the input of the pulse signal light is adjusted to be approximately π, the relative relationship of the probe light at the output ends of both arms Since the typical phase difference is inverted, the probe light appears in the output light. In this way, it is possible to generate light having the probe wavelength λp having a light intensity pattern similar to the light intensity pattern of the pulse signal light. It is possible to realize wavelength conversion for converting the optical carrier wavelength of the signal from λs to λp.

  When the probe light is pulsed light, the above-described wavelength conversion device also operates as an optical gate device that gates the probe pulsed light with the pulse signal light. That is, by using the semiconductor optical intermodulation elements XGM, XAM, and XPM, a logical operation element for the probe light and the pulse signal light can be easily realized.

  In optical signal processing using such a semiconductor optical intermodulation element, it is necessary to monitor the modulation amount of the semiconductor optical intermodulation element in order to obtain stable signal processing.

  For example, in a wavelength converter using a Mach-Zehnder interferometer in which SOAs are arranged on both arms, the following configuration is employed for monitoring the operating point of each SOA on the arms. That is, in addition to signal light (or control light in the case of an optical switch or optical gate) and probe light, relatively weak light (monitor light) of the third wavelength is incident on the SOAs on both arms. Utilizing the fact that the monitor light is modulated by the signal light with the modulation degree of the same or constant proportional relationship as the probe light. Both sideband components of the monitor light are separated from the output light of the MZI and its intensity is measured, and the applied current of the SOA on one arm is controlled based on the result.

Further, as a configuration for stabilizing the characteristics of the optical modulator, a configuration for monitoring the output signal light of the optical modulator and controlling the bias of the optical modulator according to the monitoring result has been proposed (for example, Patent Document 1 and (See Patent Document 2 corresponding to this).
JP-A-8-76068 US Pat. No. 5,629,977

  The input / output characteristics of the semiconductor optical intermodulation element are affected by the applied current or drive voltage, the intensity of the input signal light, the aging of the semiconductor element itself, the ambient temperature, and the like. Therefore, it is desirable to provide a circuit mechanism that monitors the operating state of the SOA and maintains the operating point constant. Conventional methods are insufficient to monitor and control the operating state of individual SOAs, or the circuit configuration is complicated or expensive.

  In the conventional method of measuring the modulation degree of the monitor light, the modulation degree of the SOA can be measured strictly. However, it is necessary to input the monitor light of the third wavelength to the SOA, and both sides of the monitor light from the interference output light. Since it is necessary to separate the band and measure its intensity, a large-scale device such as an optical spectrum analyzer is required.

  In a wavelength division multiplexing (WDM) system, it is necessary to prepare monitor light for each signal wavelength and measure the degree of modulation. The larger the number of wavelengths, the larger the device configuration, which is not practical.

  In order to operate the semiconductor optical intermodulation element stably, it is not necessary to measure the modulation degree of the semiconductor optical intermodulation element strictly, and it is sufficient if the fluctuation of the modulation degree can be measured.

  It is an object of the present invention to provide an optical signal processing apparatus and a method for controlling a semiconductor optical intermodulation element that can control the semiconductor optical intermodulation element by monitoring the operating state of the semiconductor optical intermodulation element without monitoring light.

An optical signal processing apparatus according to the present invention includes a light intensity adjuster that adjusts the light intensity of input signal light having a signal wavelength, probe light input means that inputs probe light having a probe wavelength, and the intensity of input light having the signal wavelength. The signal light output from the light intensity adjuster and the probe light input by the probe light input means are input. Semiconductor optical intermodulation element, DC drive circuit for direct-current driving the semiconductor optical intermodulation element, high-frequency measuring instrument for measuring a high-frequency electrical signal induced in the semiconductor optical inter-modulation element, and measurement result of the high-frequency measuring instrument And a control device for controlling the light intensity adjustment amount of the light intensity adjuster.

An optical signal processing device according to the present invention includes a signal light input unit that inputs signal light of a signal wavelength, a probe light input unit that inputs probe light of a probe wavelength, the signal light and the probe light are input, Measures a semiconductor optical intermodulation element that intermodulates the probe light according to the intensity of the signal light, a DC drive circuit that DC drives the semiconductor optical intermodulation element, and a high-frequency electrical signal induced in the semiconductor optical intermodulation element A high-frequency measuring instrument and a control device that controls the DC output of the DC drive circuit according to the measurement result of the high-frequency measuring instrument are provided.

An optical signal processing apparatus according to the present invention is an interferometer that receives signal light of a signal wavelength and probe light of a probe wavelength, and includes first and second arms, and the input signal light is the first arm. The input probe light is divided into two, one is propagated through the first arm, the other is propagated through the second arm, and the interferometer is disposed on the first arm of the interferometer, A first semiconductor optical intermodulation element that intermodulates the probe light according to the light intensity of the signal light, an optical filter that extracts component light of the probe wavelength from the interference output light of the interferometer, and an input to the interferometer A light intensity adjuster for adjusting the light intensity of the previous signal light, a direct current drive circuit for direct current driving the first semiconductor optical intermodulation element, and high-frequency electricity induced in the first semiconductor optical intermodulation element a high frequency measuring device for measuring the signal According measurement result of the frequency measurement device, characterized by comprising a controller for controlling the light intensity adjustment of the light intensity regulator.

The method for controlling a semiconductor optical intermodulation element according to the present invention is a method for controlling a semiconductor optical intermodulation element that intermodulates probe light having a probe wavelength according to the intensity of signal light having a signal wavelength so as to stably operate. A high-frequency electric signal induced by optical input to the semiconductor optical intermodulation element is measured. Then, the light intensity of the signal light to be input to the semiconductor optical intermodulation element is adjusted according to the magnitude of the measured high-frequency electrical signal .

The method for controlling a semiconductor optical intermodulation element according to the present invention controls the semiconductor optical intermodulation element that intermodulates the probe light having the probe wavelength according to the intensity of the signal light having the signal wavelength to operate stably under direct current drive. Is the method. A high-frequency electrical signal induced by light input to the half-light intermodulation element is measured. Then, the drive DC voltage of the semiconductor optical intermodulation element is adjusted according to the magnitude of the measured high-frequency electrical signal .

  According to the present invention, the operating state of the semiconductor optical intermodulation element can be constantly monitored, and the operating point can be maintained constant. The amount of intermodulation with respect to the probe light can be kept constant.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic block diagram of a first embodiment of the present invention. Signal light having a wavelength λs is input to the input terminal 10 from a signal light source or an optical transmission path (not shown), and probe light having a probe wavelength λp is input to the input terminal 12. The probe wavelength λp is different from the signal wavelength λs. In this embodiment, the probe light is composed of continuous (CW) light or an optical pulse clock synchronized with a signal light pulse input to the input terminal 10. Here, for easy understanding, it is assumed that the probe light is CW light.

  The signal wavelength λs is set to a wavelength that is absorbed by the DC-driven semiconductor optical amplifier 18, and the probe wavelength λp is set to a wavelength having a gain by the DC-driven semiconductor optical amplifier 18.

  The signal light is input from the input terminal 10 to the variable optical attenuator (or variable optical amplifier capable of changing the gain) 14 that can change the attenuation rate. The WDM optical coupler 16 combines the output light (signal light) of the variable optical attenuator 14 and the probe light from the input terminal 12 and applies the combined light to the SOA 18.

  As will be described later, a direct current is applied to the SOA 18. The SOA 18 in this state has a gain with respect to the probe wavelength λp. The SOA 18 induces carriers by the input of the signal light having the wavelength λs, and the density of the induced carriers varies according to the intensity fluctuation of the input light having the wavelength λs. Due to the carrier fluctuation, the SOA 18 modulates the gain and phase of the input probe light by mutual gain modulation (XGM) and mutual phase modulation (XPM), respectively. The output light of the SOA 18 is applied to the optical bandpass filter 20 that extracts the probe wavelength λp. The optical bandpass filter 20 extracts probe light whose gain and phase are modulated by signal light pulses. The probe wavelength light extracted by the optical bandpass filter 20, that is, the probe light whose gain and phase are modulated by the SOA 18 is output to the outside from the output terminal 22.

  When there is an optical pulse of signal light, the gain of the SOA 18 at the probe wavelength increases, and the SOA 18 optically amplifies the probe light with a large gain. On the other hand, when there is no optical pulse of signal light, the gain at the probe wavelength of the SOA 18 is suppressed, and the SOA 18 amplifies the probe light with a smaller gain. Accordingly, the probe light output from the SOA 18 has a light intensity pattern obtained by inverting the light intensity pattern of the signal light, and the SOA 18 functions as a logic inversion element. Thus, the SOA 18 functions as an all-optical signal processing device that controls another optical signal by an optical signal. When the probe light is CW, the SOA 18 functions as a wavelength conversion element that converts the wavelength of the optical carrier of the signal from λs to λp.

The SOA 18 includes electrodes 18a and 18b. The electrode 18b is connected to ground. The constant current source 24 generates a current I _dr that drives the SOA 18. The output current I _dr of the constant current source 24 is applied to the electrode 18a of the SOA 18 via the inductance or reactor 26.

  The electrode 18 a is also connected to a high frequency voltage monitor 32 via a capacitor 28 and an electrical band pass filter 30. A portion composed of the inductance 26 and the capacitor 28 is called a so-called bias tee. The center frequency of the electric bandpass filter 30 is set to a frequency corresponding to the clock frequency f0 when the pulse signal light input to the SOA 18 is in the RZ format, and half the clock frequency f0 when the pulse signal light is in the NRZ format. A frequency corresponding to f0 / 2 is set.

A high frequency with an amplitude determined according to the drive current I _dr of the SOA 18 and the light intensity of the light (signal light and probe light) input to the SOA 18 is induced in the electrode 18a. When the drive current I _{dr of the} SOA 18 and the light intensity of the probe light are constant, the amplitude of the induced high frequency depends on the light intensity of the signal light input to the SOA 18. The high frequency induced in the electrode 18a is applied to the high frequency power monitor 32 via the capacitor 28 and the band pass filter 30, and the high frequency power monitor 32 measures the high frequency power. The high frequency power measured by the high frequency power monitor 32 indicates the operating state of the SOA 18.

  The control device 34 controls the attenuation rate of the variable optical attenuator 14 so that the high frequency power measured by the high frequency power monitor 32 is maintained constant. For example, when the high frequency power measured by the high frequency power monitor 32 increases, the control device 34 increases the attenuation rate of the variable optical attenuator 14. As a result, the light intensity of the signal light input to the SOA 18 decreases, the amplitude of the high frequency induced in the electrode 18a decreases, and the high frequency power measured by the high frequency power monitor 32 decreases. Conversely, when the high frequency power measured by the high frequency power monitor 32 decreases, the control device 34 decreases the attenuation rate of the variable optical attenuator 14. By such feedback control, the operating point of the SOA 18 can be kept constant.

  Although this embodiment is not suitable for measuring the absolute modulation degree when two lights interact with each other in the SOA 18, the relative change can be monitored and the SOA 18 can be controlled so as to reduce the change. . That is, in this embodiment, the operation of the SOA 18 can be constantly monitored, the operating point can be stabilized, and as a result, the amount of intermodulation with respect to the probe light can be maintained constant.

In the embodiment shown in FIG. 1, in accordance with electric power of the high frequency signal generated by the SOA 18, has been controlling the intensity of the input signal light of SOA 18, may be controlling the drive current I _dr of SOA 18, or input control of SOA 18 Both the light intensity and the drive current I _dr of the SOA 18 may be controlled.

  When the probe light is direct current, and when the probe light is pulsed light and the fundamental frequency thereof is the same as the fundamental frequency of the control light, the high frequency induced in the electrode 18a represents the amplitude of the signal light. The band pass filter 30 may be omitted. When the probe light is pulse light and its fundamental frequency is different from the fundamental frequency of the signal light, it is necessary to extract a high frequency component induced in the electrode 18a by the band pass filter 30 according to the signal light.

  When the probe light is a return-to-zero (RZ) light pulse having a constant repetition and constant amplitude, and the signal light is a data-modulated light pulse having the same basic repetition frequency as the probe light, the light of the signal light It is necessary to adjust the timings of both the pulse and the probe light so that the light enters the SOA 18 at the same time. In this case, the embodiment shown in FIG. 1 functions as an optical element that gates the probe light with the signal light, or an arithmetic element that performs a logical operation on the signal light and the probe light.

  In the embodiment shown in FIG. 1, the signal light and the probe light are propagated in the same direction in the SOA 18, but they may be propagated in the opposite directions in the SOA 18.

  Next, an embodiment in which EAM is used instead of SOA will be described. FIG. 2 shows a schematic block diagram of the embodiment.

  Signal light having a wavelength λs is input to the input terminal 110 from a signal light source or an optical transmission path (not shown), and probe light having a probe wavelength λp is input to the input terminal 112. The probe wavelength λp is different from the signal wavelength λs. In this embodiment, the probe light is composed of continuous (CW) light or an optical pulse clock synchronized with a signal light pulse input to the input terminal 110. Both the signal wavelength λs and the probe wavelength λp are set to wavelengths absorbed by the reverse-biased EAM 118.

  The WDM coupler 116 combines the signal light from the input terminal 110 and the probe light from the input terminal 112, and applies the combined light to the EAM 118.

  The EAM 118 is reverse-biased as will be described later. The reverse-biased EAM 118 absorbs the input of the signal light having the wavelength λs and induces carriers by the absorption. The induced carrier density varies according to the intensity variation of the input light having the wavelength λs. Due to the carrier fluctuation, the EAM 118 modulates the light intensity of the input probe light by cross absorption modulation (XAM).

  The output light from the EAM 118 is applied to the optical bandpass filter 120 that extracts the probe wavelength λp. The optical bandpass filter 120 extracts the probe light whose gain is modulated by the signal light pulse. The light of the probe wavelength λp extracted by the optical bandpass filter 120, that is, the probe light whose light intensity is modulated by the EAM 118 is output to the outside from the output terminal 122.

  When there is an optical pulse of signal light, the EAM 118 absorbs light at the probe wavelength, and the EAM 118 transmits the probe light with a low absorption rate. On the other hand, when there is no optical pulse of signal light, the absorption rate at the probe wavelength of the EAM 118 remains large, and the EAM 118 attenuates the probe light with a larger absorption rate. Therefore, the EAM 118 modulates the light intensity of the probe light according to the intensity pattern of the signal light. When the probe light is CW, the light intensity pattern of the probe light output from the EAM 118 is a light intensity pattern that is very close to the light intensity pattern of the signal light.

  Thus, the EAM 118 also acts as an all-optical signal processing device that controls another optical signal by an optical signal, like the SOA 18. When the probe light is CW, the EAM 118 functions as a wavelength conversion element that converts the wavelength of the optical carrier of the signal from λs to λp.

  The EAM 118 includes electrodes 118a and 118b. The electrode 118b is connected to ground. The DC voltage source 124 generates a DC voltage that reversely biases the pn junction of the EA modulator 118. The output voltage of the DC voltage source 124 is applied to the electrode 118a of the EAM 118 via the inductance 126.

  The electrode 118a is also connected to a high frequency voltage monitor 132 via a capacitor 128 and an electrical bandpass filter 130. A portion composed of the inductance 126 and the capacitor 128 is called a so-called bias tee. The center frequency of the electric bandpass filter 130 is set to a frequency corresponding to the clock frequency f0 when the pulse signal light input to the EAM 118 is in the RZ format, and is half the clock frequency f0 when the pulse signal light is in the NRZ format. A frequency corresponding to f0 / 2 is set.

  A high frequency with an amplitude determined according to the voltage applied to the EAM 118 and the light intensity of light (signal light and probe light) input to the EAM 118 is induced in the electrode 118a. When the drive voltage of the EAM 118 and the light intensity of the probe light are constant, the amplitude of the induced high frequency depends on the light intensity of the signal light input to the EAM 118. The high frequency induced in the electrode 118a is applied to the high frequency power monitor 132 via the capacitor 128 and the band pass filter 130, and the high frequency power monitor 132 measures the high frequency power. The high frequency power measured by the high frequency power monitor 132 indicates the operating state of the EAM 118.

  The control device 134 controls the output voltage of the DC voltage source 124 so that the high frequency power measured by the high frequency power monitor 132 is maintained constant. For example, it is assumed that the high frequency power measured by the high frequency power monitor 132 has increased. In this case, the light intensity of the signal light incident on the EAM 118 is increased, and as a result, the change in the absorptance with respect to the probe light becomes too large. Therefore, the control device 134 reduces the output voltage of the DC voltage source 124. When the reverse bias voltage of the EAM 118 is lowered, the change in the absorptance with respect to the probe light is reduced, and the amount of carriers generated with respect to the incident signal light is also reduced. As a result, the high frequency power measured by the high frequency power monitor 132 is reduced. Conversely, when the high-frequency power measured by the high-frequency power monitor 132 decreases, the control device 134 increases the output voltage of the DC voltage source 124. By such feedback control, the operating point of the EAM 118 can be maintained constant. In this embodiment, the operation of the EAM 118 can be constantly monitored, and the XAM amount with respect to the probe light can be kept constant.

  In the embodiment shown in FIG. 2, the reverse bias voltage of the EAM 118 is controlled in accordance with the amount of high-frequency power generated by the EAM 118, but the signal before entering the EAM 118 by a variable attenuator or the like as in the embodiment shown in FIG. The light intensity of light may be controlled.

  Also in the embodiment shown in FIG. 2, when the probe light is DC, and when the probe light is pulsed light and the fundamental frequency thereof is the same as the fundamental frequency of the control light, the high frequency induced in the electrode 118a is a signal. Since it represents the amplitude of light, the band-pass filter 130 may be omitted. When the probe light is pulse light and its fundamental frequency is different from the fundamental frequency of the signal light, it is necessary to extract a high frequency component induced in the electrode 118a by the band pass filter 130 according to the signal light.

  When the probe light is an RZ optical pulse having a constant repetition and a constant pulse amplitude, and the signal light is a data-modulated optical pulse having the same basic repetition frequency as the probe light, the optical pulse of the signal light and the light of the probe light It is necessary to adjust both timings so that the pulses are incident on the EAM 118 at the same time. In this case, like the embodiment shown in FIG. 1, the embodiment shown in FIG. 2 functions as an optical element that gates the probe light with the signal light, or an arithmetic element that logically calculates the signal light and the probe light.

  Although the signal light and the probe light are propagated in the same direction in the EAM 118, they may be propagated in the opposite directions in the EAM 118.

  Next, an embodiment in which the present invention is applied to a wavelength converter or an optical gate having a Mach-Zehnder interferometer (MZI) structure in which SOAs are arranged on both arms will be described. In this embodiment, SOA XPM is used. FIG. 3 shows a schematic configuration diagram thereof.

  Signal light having a wavelength λs is input to the input terminal 210 from a signal light source or an optical transmission path (not shown), and probe light having a probe wavelength λp is input to the input terminal 212. The probe wavelength λp is different from the signal wavelength λs. In this embodiment, the probe light is composed of continuous (CW) light or an optical pulse clock synchronized with a signal light pulse input to the input terminal 210. Here, for easy understanding, it is assumed that the probe light is CW light and the embodiment shown in FIG. 3 is used as a wavelength converter.

  The signal wavelength λs is set to a wavelength that is absorbed by the SOA 218 that is DC-driven, and the probe wavelength λp is set to a wavelength that has a gain in the SOAs 218 and 240 that are DC-driven.

  The signal light is input from the input terminal 210 to the optical coupler 216 via the variable optical attenuator (or variable optical amplifier capable of changing the gain) 214 that can change the attenuation factor. The probe light is input from the input terminal 212 to the optical coupler 242 and is divided into two by the optical coupler 242. The optical coupler 216 combines the signal light from the variable optical attenuator 214 and one probe light divided by the optical coupler 242 and applies the resultant light to the SOA 218. The other probe light divided by the optical coupler 242 is applied to another SOA 240. SOA 218 is located on one arm of MZI and SOA 240 is located on another arm of MZI. Eventually, signal light and probe light are incident on the SOA 218, and only probe light is incident on the SOA 240.

A direct current I _dr1 is applied to the SOA 118, and a direct current I _dr2 is applied to the SOA 240. In FIG. 3, a direct current source for the SOA 140 is omitted. Thereby, the SOAs 218 and 240 have a gain with respect to the probe wavelength λp. Since the signal light is also incident on the SOA 218, the SOA 218 modulates the gain and phase of the probe light according to the light intensity fluctuation of the incident signal light as described in the embodiment shown in FIG. Here, XPM is used. The drive current of the SOA 218, the light intensity of the signal light, and the light intensity of the probe light are adjusted in advance so that the optical phase of the probe light differs by π depending on the presence or absence of the signal light.

  The multiplexer 244 multiplexes the output lights of the SOAs 218 and 240 and applies the multiplexed light to the optical bandpass filter 220 that transmits the probe wavelength light. The optical bandpass filter 220 extracts light having the probe wavelength λp from the output light from the multiplexer 244 and supplies the light to the output terminal 222.

  The intensity of the probe wavelength light at the output of the multiplexer 244 varies depending on whether or not the signal light (its optical pulse) exists. This is due to the difference in optical path length between the arm where the SOA 218 is placed and the arm where the SOA 240 is placed in the MZI. When the difference in the optical path length between the arms is zero, the intensity of the probe wavelength light at the output of the multiplexer 244 increases when no signal light is present, and decreases when the signal light is present. When the difference in optical path length between both arms is π, the intensity of the probe wavelength light at the output of the multiplexer 244 is weak when no signal light is present, and is strong when signal light is present. Needless to say, both forms of output light can be obtained by replacing the multiplexer 244 with a multiplexer / demultiplexer and providing both destructive output and constructive output in the MZI.

  In the embodiment shown in FIG. 3 as well, the light intensity of the signal light input to the SOA 218 is adjusted as in the embodiment shown in FIG. The configuration for this is substantially the same as the embodiment shown in FIG.

The SOA 218 includes electrodes 218a and 218b. The electrode 218b is connected to ground. The constant current source 224 generates a current I _dr1 that drives the SOA 218. Output current I _dr1 of the constant current source 224 is applied to SOA218 electrode 218a through the inductance or reactor 226.

  The electrode 218 a is also connected to a high frequency voltage monitor 232 via a capacitor 228 and an electrical band pass filter 230. A portion composed of the inductance 226 and the capacitor 228 is called a so-called bias tee. The center frequency of the electrical bandpass filter 230 is set to a frequency corresponding to the clock frequency f0 when the pulse signal light input to the SOA 218 is in the RZ format, and half the clock frequency f0 when the pulse signal light is in the NRZ format. A frequency corresponding to f0 / 2 is set.

The electrode 218 a is induced with a high frequency with an amplitude determined according to the drive current I _dr1 of the SOA 218 and the light intensity of the light (signal light and probe light) input to the SOA 218. If the light intensity of the drive current I _dr1 and probe light SOA218 is constant, the high frequency amplitude induced depends on the intensity of the signal light input to SOA218. The high frequency induced in the electrode 218a is applied to the high frequency power monitor 232 via the capacitor 228 and the band pass filter 230, and the high frequency power monitor 232 measures the high frequency power. The high frequency power measured by the high frequency power monitor 232 indicates the operating state of the SOA 218.

  The control device 234 controls the attenuation rate of the variable optical attenuator 214 so that the high frequency power measured by the high frequency power monitor 232 is kept constant. For example, when the high frequency power measured by the high frequency power monitor 232 increases, the control device 234 increases the attenuation rate of the variable optical attenuator 214. As a result, the light intensity of the signal light input to the SOA 218 decreases, the amplitude of the high frequency induced in the electrode 218a decreases, and the high frequency power measured by the high frequency power monitor 232 decreases. Conversely, when the high frequency power measured by the high frequency power monitor 232 decreases, the control device 234 decreases the attenuation rate of the variable optical attenuator 214. By such feedback control, the amount of XPM for the probe light by the SOA 218 can be kept constant.

In the embodiment shown in FIG. 3, in accordance with electric power of the high frequency signal generated by SOA218, was controlling the intensity of the input signal light SOA218, may be controlling the drive current I _dr1 of SOA218, or input control of SOA218 it may control both the drive current I _dr1 of the intensity of the light and SOA218.

FIG. 4 shows a schematic configuration diagram of an embodiment in which the embodiment shown in FIG. 3 is modified to control the drive current _Idr1 instead of adjusting the light intensity of the signal light. The same components as those in FIG. 3 are denoted by the same reference numerals.

The variable optical attenuator 214 is removed, and a control device 246 in place of the control device 234 controls the output current I _dr1 of the DC current source 224 so that the high frequency power measured by the high frequency power monitor 232 is constant.

  Although the embodiment in the case of wavelength conversion has been mainly described in Embodiment 1-4, each of the above embodiments can also operate as an optical gate switch or an optical logic operation device. The present invention can be widely applied to optical devices such as gate switches and optical logic operation devices.

  Although the invention has been described with reference to specific illustrative embodiments, various modifications and alterations may be made to the above-described embodiments without departing from the scope of the invention as defined in the claims. This is obvious to an engineer in the field to which the present invention belongs, and such changes and modifications are also included in the technical scope of the present invention.

1 shows a schematic configuration diagram of Embodiment 1 of the present invention. FIG. The schematic block diagram of Example 2 of this invention is shown. The schematic block diagram of Example 3 of this invention is shown. The schematic block diagram of Example 4 of this invention is shown.

Explanation of symbols

10: Signal light input terminal 12: Probe light input terminal 14: Variable optical attenuator 16: WDM optical coupler 18: Semiconductor optical amplifier (SOA)
18a, 18b: Electrode 20: Optical band pass filter 22: Output terminal 24: Constant current source 26: Inductance 28: Capacitor 30: Electric band pass filter 32: High frequency power monitor 34: Controller 110: Signal light input terminal 112: Probe Optical input terminal 116: WDM optical coupler 118: electroabsorption optical modulator (EAM)
118a, 118b: Electrode 120: Optical band pass filter 122: Output terminal 124: DC voltage source 126: Inductance 128: Capacitor 130: Electric band pass filter 132: High frequency power monitor 134: Controller 210: Signal light input terminal 212: Probe Optical input terminal 214: Variable optical attenuator 216: WDM optical coupler 218: Semiconductor optical amplifier (SOA)
218a, 218b: Electrode 220: Optical band pass filter 222: Output terminal 224: Constant current source 226: Inductance or reactor 228: Capacitor 230: Electric band pass filter 232: High frequency power monitor 234: Controller 240: Semiconductor optical amplifier (SOA) )
242: optical coupler 244: multiplexer 246: control device

Claims (22)

A light intensity adjuster (14) for adjusting the light intensity of the input signal light of the signal wavelength;
Probe light input means (12) for inputting probe light having a probe wavelength;
A semiconductor optical intermodulation element that intermodulates the input light of the probe wavelength according to the intensity of the input light of the signal wavelength, the signal light output from the light intensity adjuster (14), and the probe light input means Semiconductor optical intermodulation element (18) to which the input probe light is input
When,
A DC driving circuit (24) for DC driving the semiconductor optical intermodulation element (18);
A high-frequency measuring instrument (32) for measuring a high-frequency electrical signal induced in the semiconductor optical intermodulation element (18);
A control device (34) for controlling the light intensity adjustment amount of the light intensity adjuster (14) according to the measurement result of the high frequency measuring instrument (32).
An optical signal processing device comprising:   The optical signal processing apparatus according to claim 1, further comprising an optical filter (20) for extracting an optical component of the probe wavelength from the output light of the semiconductor optical intermodulation element (18).   The semiconductor optical intermodulation element (18) includes an electrode (18a), the output of the DC drive circuit (24) is connected to the electrode (18a) via an inductance (26), and the electrode (18a) 3. The optical signal processing device according to claim 1, wherein the optical signal processing device is connected to an input of the high-frequency measuring instrument (32) via a capacitor (28).   The optical signal processing apparatus according to any one of claims 1 to 3, wherein the light intensity adjuster comprises a variable optical attenuator (14).   The optical signal processing apparatus according to claim 1, wherein the light intensity adjuster includes a variable optical amplifier.   6. The optical signal processing apparatus according to claim 1, wherein the semiconductor optical intermodulation element comprises a semiconductor optical amplifier. Signal light input means (110) for inputting signal light of a signal wavelength;
Probe light input means (112) for inputting probe light having a probe wavelength;
A semiconductor optical intermodulation element (118) that receives the signal light and the probe light and intermodulates the probe light in accordance with the intensity of the signal light;
A direct current drive circuit (124) for direct current driving the semiconductor optical intermodulation element (118);
Frequency measuring device for measuring a high-frequency electrical signal induced in the semiconductor optical intermodulation element (118) and (132),
A control device (134) for controlling the direct current output of the direct current drive circuit (124) according to the measurement result of the high frequency measuring device (132).
An optical signal processing device comprising:   The optical signal processing apparatus according to claim 7, further comprising an optical filter (120) for extracting an optical component of the probe wavelength from the output light of the semiconductor optical intermodulation element (118).   The semiconductor optical intermodulation element (118) includes an electrode (118a), the output of the DC drive circuit (124) is connected to the electrode (118a) via an inductance (126), and the electrode (118a) 9. The optical signal processing device according to claim 7, wherein the optical signal processing device is connected to an input of the high-frequency measuring device (132) via a capacitor (128).   Further, the signal light input by the signal light input means (110) and the probe light input by the probe light input means (112) are combined, and the combined light is combined with the semiconductor optical intermodulation element (118). 10. An optical signal processing apparatus according to claim 7, further comprising an optical coupler (116) applied to the optical signal.   11. The optical signal processing apparatus according to claim 7, wherein the semiconductor optical intermodulation element includes one of a semiconductor optical amplifier and an electroabsorption optical intermodulator. An interferometer for inputting signal light having a signal wavelength and probe light having a probe wavelength. The interferometer includes first and second arms. The input signal light propagates through the first arm, and the input probe light is divided into two. Interferometers (216, 242, 244), one propagating through the first arm and the other propagating through the second arm,
A first semiconductor optical intermodulation element (218) disposed on the first arm of the interferometer and intermodulating the probe light according to the light intensity of the signal light;
An optical filter (220) for extracting component light of the probe wavelength from the interference output light of the interferometer;
A light intensity adjuster (214) for adjusting the light intensity of the signal light before being input to the interferometer;
A DC driving circuit (224) for DC driving the first semiconductor optical intermodulation element (218);
A high-frequency measuring instrument (232) for measuring a high-frequency electrical signal induced in the first semiconductor optical intermodulation element (218);
A control device (234) for controlling the light intensity adjustment amount of the light intensity adjuster (214) according to the measurement result of the high frequency measuring instrument (232).
An optical signal processing device comprising: An interferometer for inputting signal light having a signal wavelength and probe light having a probe wavelength. The interferometer includes first and second arms. The input signal light propagates through the first arm, and the input probe light is divided into two. Interferometers (216, 242, 244), one propagating through the first arm and the other propagating through the second arm,
A first semiconductor optical intermodulation element (218) disposed on the first arm of the interferometer and intermodulating the probe light according to the light intensity of the signal light;
An optical filter (220) for extracting component light of the probe wavelength from the interference output light of the interferometer;
A DC driving circuit (224) for DC driving the first semiconductor optical intermodulation element (218);
A high-frequency measuring instrument (232) for measuring a high-frequency electrical signal induced in the first semiconductor optical intermodulation element (218);
A control device (246) for controlling the DC output of the DC drive circuit (224) according to the measurement result of the high-frequency measuring device (232).
An optical signal processing device comprising: The interferometer is
An optical demultiplexer (242) for dividing the input probe light into two;
A first optical multiplexer (216) that combines the input signal light and one output light of the optical demultiplexer (242), and outputs the combined light to the first arm;
Second optical multiplexer (244) for multiplexing the output lights of the first and second arms
The optical signal processing apparatus according to claim 12 or 13, wherein the other output light of the optical demultiplexer (242) is input to the second arm.   The semiconductor optical intermodulation element (218) includes an electrode (218a), the output of the DC drive circuit (224) is connected to the electrode (218a) via an inductance (226), and the electrode (218a) 14. The optical signal processing apparatus according to claim 12, wherein the optical signal processing apparatus is connected to an input of the high-frequency measuring instrument (232) through a capacitor (228).   13. The optical signal processing device according to claim 12, wherein the light intensity adjuster comprises a variable optical attenuator (214).   13. The optical signal processing apparatus according to claim 12, wherein the light intensity adjuster comprises a variable optical amplifier.   18. The optical signal processing apparatus according to claim 13, wherein the semiconductor optical intermodulation element includes any one of a semiconductor optical amplifier and an electroabsorption optical modulator.   The optical signal processing device according to any one of claims 13 to 18, further comprising a second semiconductor optical intermodulation element (240) disposed on the second arm. A method of controlling a semiconductor optical intermodulation element that intermodulates probe light of a probe wavelength according to the intensity of signal light of a signal wavelength so as to stably operate,
Measure the high-frequency electrical signal induced by the optical input to the semiconductor optical intermodulation element,
A method for controlling a semiconductor optical intermodulation element, comprising adjusting the light intensity of signal light to be input to the semiconductor optical intermodulation element in accordance with the magnitude of the measured high-frequency electrical signal . A method of controlling a semiconductor optical intermodulation element that intermodulates probe light of a probe wavelength according to the intensity of signal light of a signal wavelength under direct current drive so as to stably operate,
Measure the high-frequency electrical signal induced by the light input to the half-light intermodulation element,
According magnitude of the measured high-frequency electrical signals, the control method of the semiconductor light intermodulation element and adjusts the driving DC voltage of the semiconductor optical intermodulation element. The method according to claim 20 or 21, wherein the high-frequency electric signal has a frequency corresponding to a fluctuation component frequency of the signal light input to the semiconductor optical intermodulation element.

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