JP2011055330A - Optical switch adjusting circuit, eye opening monitor circuit, optical signal transmitting apparatus, full optical signal reproducing apparatus, otdm-demux device and optical switch adjusting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adjust dynamic operation of an optical switch, easily, at low cost, within a small size and with high accuracy. <P>SOLUTION: An optical switch adjusting circuit 2 includes: a distributor 3 which splits input signal light INL and outputs it as reference signal light RL; a distributor 4 which splits output signal light OUTL from an optical switch 1 and outputs it as monitor signal light ML; an optical phase shifter 5 for shifting a phase relationship between the reference signal light RL and the monitor signal light ML; an interference signal light generator 6 for overlapping and interfering the reference signal light RL and the monitor signal light ML phase-shifted by the optical phase shifter 5; a photodetector 7 for detecting power of interference signal light IL; and a phase bias adjusting section 8 for feeding such a phase bias condition as to maximize an eye opening of the output signal light OUTL back to the optical switch 1 in accordance with a time average value of light power detected by the photodetector 7. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention mainly relates to an adjustment circuit for an optical switch at a communication speed of 10 Gbps class or higher.

  In recent years, with the explosive increase in Internet demand, the required communication capacity is increasing, and optical communication with a transmission speed exceeding 10 Gbps / ch is becoming mainstream even for commercial use. Under such circumstances, a technique for managing and controlling the quality of an output signal from an optical switch that modulates and gates an optical signal at high speed is becoming more and more important. This is because with the increase in transmission speed, signal quality is more sensitively deteriorated with respect to temperature changes and changes in structure / materials with time. In general, an optical interference type optical switch is often used for optical signal processing of 10 Gbps class or more, but it is used for adjusting the output waveform quality (driving state) of the optical interference type optical switch, that is, optimizing the phase bias. The most direct and reliable method is to feed back the result of waveform observation with an oscilloscope or the result of bit error rate measurement with an error detector.

  However, this method is difficult to adopt from the viewpoint of cost, size, power consumption, etc. when used in an actual network, and providing a more practical method to consumers instead of this method It was still a big issue. As a more practical method, an adjustment method of an interference optical switch is described in Patent Documents 1 to 6, and an optical signal quality (extinction ratio) monitoring method is described in Patent Document 7.

  The basic principle of the method described in Patent Document 1 to Patent Document 4 is to monitor the average output light power of the optical switch and compare this average output light power with the value recorded in a table prepared in advance. Thus, the optimum state of the optical switch is maintained. The method described in Patent Document 5 is a method of optimizing the optical gate operation by monitoring the optical spectrum peak of the weak continuous light input to the optical switch. The method described in Patent Document 6 monitors the interference light between the signal light leaked from the optical waveguide and the radiated light radiated from the optical waveguide inside the optical gate, and performs the optical gate operation according to the intensity change of the interference light. How to control. The method described in Patent Document 7 causes the optical gate output light to interfere with the light frequency-modulated at a low frequency, extracts only the low-frequency component of the interference light, and measures the dynamic light extinction ratio with high accuracy. It is a method to do.

Japanese Patent Laid-Open No. 2001-075062 JP 09-073055 A Japanese Patent Laid-Open No. 05-249418 Japanese Patent Laid-Open No. 04-294318 JP 2000-029081 A JP-A-10-221664 JP 07-322010 A

However, the methods described in Patent Documents 1 to 4 monitor only the average output light power from the optical switch, and adjust the optical switch only with the value of the average output light power and the value of the table. However, it is difficult to adjust dynamic signal characteristics with high accuracy.
The method described in Patent Document 5 is effective in that dynamic signal characteristics can be monitored with time average information called optical spectrum, but there is a problem that an optical component for separating optical spectral components is required separately. was there.

Patent Document 6 describes a method of monitoring and controlling the state of an optical switch by monitoring the intensity of a part of a spatial light interference pattern whose phase has been adjusted by the internal structure of a module or the like. However, the method described in Patent Document 6 has a problem that it is structurally difficult to cut out only a specific interference pattern and to adjust and stabilize the phase of light.
The method described in Patent Document 7 can monitor the extinction ratio with high accuracy by interference of light. However, since it is necessary to distinguish the mark level and the space level on the time axis, the bit rate becomes high. There is a problem that a high-speed circuit for the identification is required.

  An object of the present invention is to provide an optical switch adjustment circuit capable of adjusting the dynamic operation of an optical switch simply, at low cost, in a small size, and with high accuracy.

  The optical switch adjustment circuit of the present invention includes a first distribution unit that branches signal light input to the optical switch and outputs it as reference signal light, and branches output signal light from the optical switch as monitor signal light. Second distribution means for outputting, phase shifter for shifting the phase relationship between the reference signal light and the monitor signal light, reference signal light phase-shifted by the optical phase shifter, and output from the second distribution means Interference signal light generating means for causing interference by superimposing the monitor signal light, an optical detector for detecting the power of the interference signal light output from the interference signal light generating means, and an optical signal detected by the optical detector Phase bias adjusting means for feeding back to the optical switch a phase bias condition that maximizes the eye opening of the output signal light according to a time average value of optical power. It is characterized in that to obtain.

  The eye opening monitor circuit of the present invention includes a first distribution unit for branching signal light input to the optical switch and outputting it as reference signal light, and a monitor signal for branching output signal light from the optical switch. Second distribution means for outputting as light, phase shifter for shifting the phase relationship between the reference signal light and the monitor signal light, reference signal light phase-shifted by the optical phase shifter and the second distribution means The interference signal light generating means for superimposing the monitor signal light output from the interference signal, the photodetector for detecting the power of the interference signal light output from the interference signal light generating means, and the phase difference by the phase shifter Measure the dependence of the time average power of the interference signal light detected by the photodetector, calculate the phase bias value of the optical switch from the measurement results, Is characterized in further comprising a calculation means for the phase bias value to derive an eye opening or the output extinction ratio of the output signal light has.

  The optical switch adjustment method of the present invention includes a first distribution procedure for branching signal light input to an optical switch to be a reference signal light, and branching output signal light from the optical switch to monitor signal light. And a phase shift procedure for shifting the phase relationship between the reference signal light and the monitor signal light, and the phase-shifted reference signal light and the monitor obtained by the second distribution procedure. Interference signal light generation procedure for superimposing signal light and causing interference, detection procedure for detecting the power of the interference signal light obtained in this interference signal light generation procedure, and time average of the optical power detected in this detection procedure And a phase bias adjustment procedure for feeding back to the optical switch a phase bias condition that maximizes the eye opening of the output signal light according to the value.

  According to the present invention, it is possible to adjust the dynamic operation of the optical switch, that is, to optimize the phase bias, in a simple, low-cost, small-size and high-accuracy manner, and automatically adjust the eye opening of the output signal light. Can be maximized.

1 is a block diagram of an apparatus including an optical switch adjustment circuit according to a first embodiment of the present invention. It is a figure which shows the relationship between the phase bias and output light extinction ratio in the interference type optical switch in the 1st Embodiment of this invention. The figure which shows the average optical power of the interference signal light with respect to the phase difference of reference signal light and monitor signal light in the 1st Embodiment of this invention, and interference signal with respect to the phase difference of reference signal light and monitor signal light It is a figure which shows the phase bias of the optical switch when the average optical power of light is the maximum or the minimum. It is a figure which shows the image which extracts the mark level or space level of data signal light in the 1st Embodiment of this invention. It is a block diagram of the optical signal transmitter containing the optical switch adjustment circuit which concerns on the 2nd Embodiment of this invention. It is a block diagram of an all-optical signal regeneration device including an optical switch adjustment circuit according to a third embodiment of the present invention. It is a block diagram of the OTDM-DEMUX apparatus containing the optical switch adjustment circuit which concerns on the 4th Embodiment of this invention. It is a block diagram of the OTDM-DEMUX apparatus containing the optical switch adjustment circuit which concerns on the 5th Embodiment of this invention. It is a block diagram of the all-optical signal reproducing | regenerating apparatus containing the optical switch adjustment circuit which concerns on the 6th Embodiment of this invention. It is a block diagram of the all-optical signal reproducing | regenerating apparatus containing the optical switch adjustment circuit which concerns on the 7th Embodiment of this invention. It is a block diagram of the all-optical signal reproducing | regenerating apparatus containing the optical switch adjustment circuit based on the 8th Embodiment of this invention.

[First Embodiment]
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an apparatus including an optical switch adjustment circuit according to a first embodiment of the present invention. The apparatus according to the present embodiment includes an optical switch 1 and an optical switch adjustment circuit 2. Examples of such an apparatus include an optical signal transmitter, an all-optical signal regeneration apparatus, or an OTDM (Optical Time Division Multiplex) -DEMUX (Demultiplexer) apparatus described later. The optical switch 1 is turned on / off according to the modulation signal D, and data-modulates the input signal light INL.

  As shown in FIG. 1, the optical switch adjustment circuit 2 branches the signal light INL input to the optical switch 1 and outputs it as the reference signal light RL, and the output signal light OUTL from the optical switch 1. A splitter 4 that is branched and output as the monitor signal light ML, an optical phase shifter 5 that shifts the phase relationship between the reference signal light RL and the monitor signal light ML, and a reference signal light RL that is phase-shifted by the optical phase shifter 5 And the monitor signal light ML are overlapped to interfere with each other, the photodetector 7 for detecting the power of the interference signal light IL, and the time average value of the optical power detected by the photodetector 7. Accordingly, the phase bias adjusting unit 8 that feeds back to the optical switch 1 a phase bias condition that maximizes the eye opening of the output signal light OUTL.

  Here, the degree of eye opening with respect to the phase bias setting value in the interference type optical switch 1, that is, the extinction ratio of the output signal light OUTL will be described. FIG. 2 shows the output light extinction ratio (intensity ratio between the mark level and the space level) with respect to the phase bias α. In FIG. 2, reference numeral 200 denotes a curve showing the relationship between the phase bias α and the output light extinction ratio. 2 indicates an eye opening of the output signal light OUTL when the phase bias α = 0.4π, 204 indicates an eye opening when the phase bias α = π, and 205 indicates the above-described phase bias α. The eye opening when it deviates from two values is shown. The dynamic phase shift amount by the optical switch 1 at the time of signal modulation is not π, but 0.6π which is less than π is assumed so as to correspond more actually. The mark rate was assumed to be 0.5. Needless to say, generality is not lost by these assumptions.

  The eye opening of the output signal light OUTL is maximized when the phase bias α of the optical switch 1 is set to a value corresponding to the peaks 201 and 202 of the curve 200. A peak 201 indicates an operating point at which the eye opening is maximized during negative logic operation (when the extinction ratio is a negative value), and the phase bias α corresponding to the peak 201 is 0.4π. A peak 202 indicates an operating point at which the eye opening becomes maximum during positive logic operation (when the extinction ratio is a positive value), and the phase bias α corresponding to the peak 202 is π.

Next, when the optical phase shifter 5 changes the phase difference θc between the reference signal light RL and the monitor signal light ML (that is, the phase difference between the reference signal light RL and the output signal light OUTL), the photodetector 7 in the average optical power P _PD of the interference signal light IL to be detected, Figure 3 shows in (a) a plot against several phase bias α comprehensively. Average In FIG 3 (A), 400 is a curve showing the relationship between the phase difference θc when the phase bias α = 0.4π and average optical power P _PD, 401 is a phase difference θc when the phase bias alpha = [pi It is a curve which shows the relationship with optical power _PPD . According to FIG. 3A, the curves 400 and 401 at α = 0.4π, π at which the eye opening of the output signal light OUTL is maximum are in a relatively wide specific θc region, and the average optical power P _PD It can be seen that the maximum value or the minimum value is taken.

Accordingly, the optical phase shifter 5 is fixed with a certain value phase difference θc between the optical reference signal RL and the monitor signal light ML, phase bias adjustment unit 8, the maximum or minimum average optical power P _PD of the interference signal light IL By adjusting the phase bias α of the optical switch 1 so that the output signal light OUTL can be maximized, the eye opening of the output signal light OUTL can be automatically maximized. This effect is that, in a general optical signal, the phase of the light is shifted from each other at the mark level and the space level after modulation, and the monitor signal light ML and the reference signal light RL are overlapped as shown in FIG. When interference is performed together, the mark level of the interference signal light IL is emphasized as shown in FIG. 4B or the space level of the interference signal light IL as shown in FIG. Is emphasized (that is, the mark level is erased).

FIG. 3B shows the phenomenon explained in FIGS. 4A to 4C more clearly. FIG. 3 (B) is plotted against the phase difference θc between the phase bias alpha, the reference signal light RL and the monitor signal light ML when the average optical power P _PD of the interference signal light IL is maximum or minimum is there. In FIG. 3 (B), 402 is a phase bias α when the average optical power P _PD of the interference signal light IL is maximum, 403 is a phase bias α when the average optical power P _PD of the interference signal light IL minimum . Reference numeral 404 denotes a positive logic operation optimum point, and reference numeral 405 denotes a negative logic operation optimum point.

According to FIG. 3B, in a certain range of the phase difference θc between the reference signal light RL and the monitor signal light ML, the phase bias α has a positive logic operation optimum point (a point at which the eye opening becomes maximum) or negative. It can be seen that the logic operation is locked at the optimum point (the point where the eye opening is maximized). Here, due to the optical hybrid, the value of the average optical power P _PD of the interference signal light IL in the different two or more phase difference θc is measured simultaneously, based on the measured value, and adjusts the phase bias α to an optimum value May be.

On the other hand, in FIG. 3 (A), the average optical power P _PD of the interference signal light IL with respect to the sweep of the phase difference θc between the optical reference signal RL and the monitor signal light ML vibrates. The vibration amplitude of the average optical power P _PD has two eye opening maxima (α = π, 0.4π) it is understood that the minimum at. Therefore, the optical phase shifter 5 sweeps the phase difference θc between the reference signal light RL and the monitor signal light ML at a low speed (several MHz or less) at a low cost, and the phase bias adjustment unit 8 detects the interference signal light IL. it may adjust the phase bias α of the optical switch 1 so that the vibration amplitude of the average optical power P _PD is minimized. Thereby, the eye opening of the output signal light OUTL can be automatically maximized.

Here, by cutting the DC component of the average optical power P _PD of the interference signal light IL, to extract only the vibration amplitude of the average optical power P _PD, it may be inserted a high-pass filter after the optical detector 7. The phase difference θc between the reference signal light RL and the monitor signal light ML may be continuously swept. Alternatively, the average optical power P _PD value of the interference signal light IL at two or more different phase differences θc may be measured simultaneously using an optical hybrid, and the vibration amplitude of the average optical power P _PD may be calculated from the measured value. Good. When the optical hybrid is used, sweeping of the phase difference θc can be made unnecessary.

Furthermore, this embodiment can also be applied as a monitor of the eye opening of the output signal light OUTL or the output light extinction ratio. To such that FIG. 3 (A), the if-dependent average optical power P _PD of the interference signal light IL with respect to the phase difference θc between the optical reference signal RL and the monitor signal light ML is known, in order to be identified the phase bias α is there.
Note that the effect of the present embodiment can be obtained in the same way regardless of whether the data signal modulation format is NRZ (Non-return-to-zero) or RZ (Return-to-zero).

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram of an optical signal transmission apparatus including an optical switch adjustment circuit according to the second embodiment of the present invention. The present embodiment more specifically describes the first embodiment.
As described in the first embodiment, the optical switch 1 is turned on / off according to the modulated electrical signal D, and data modulates the input signal light INL.

The distributor 3 branches the signal light INL input to the optical switch 1 and outputs it as the reference signal light RL. The distributor 4 branches the output signal light OUTL from the optical switch 1 and outputs it as the monitor signal light ML. The optical phase shifter 5 shifts the phase relationship between the reference signal light RL and the monitor signal light ML. The interference signal light generation unit 6 causes the reference signal light RL phase-shifted by the optical phase shifter 5 and the monitor signal light ML output from the distributor 4 to overlap and cause interference. Photodetector 7 detects the average optical power P _PD of the interference signal light IL. Here, it is assumed that the photodetector 7 has a sufficiently slow response speed (nsec order or more) with respect to the data rate of the modulated electric signal D and can observe the time average power of the data modulated signal light. Further, the input signal light INL may be a clock signal light or a continuous (CW) light.

Then, the optical phase shifter 5, and fixed to a specific value in the phase difference θc between the optical reference signal RL and the monitor signal light ML, phase bias adjustment unit 8, the average optical power P _PD of the interference signal light IL up Alternatively, the phase bias α of the optical switch 1 is adjusted so as to be minimized. Regarding the phase difference θc between the reference signal light RL and the monitor signal light ML, generally, the value of the phase difference θc that maximizes the eye opening is stored in advance in the optical phase shifter 5 only once in the initial stage of the device operation. It is necessary to keep. Here, due to the optical hybrid, the value of the average optical power P _PD of the interference signal light IL in the different two or more phase difference θc is measured simultaneously, based on the measured value, and adjusts the phase bias α to an optimum value May be.

Further, as described in the first embodiment, the optical phase shifter 5 sweeps the phase difference θc between the reference signal light RL and the monitor signal light ML at a low frequency (several MHz or less), and the phase bias adjustment unit 8, may adjust the phase bias α of the optical switch 1 so that the vibration amplitude of the average optical power P _PD of the interference signal light IL is minimized. Here, by cutting the DC component of the average optical power P _PD of the interference signal light IL, to extract only the vibration amplitude of the low frequency of the average optical power P _PD, average low cut-off frequency after the photodetector 7 A high pass filter lower than the low frequency frequency of the optical power _PPD may be inserted.

As described in the first embodiment, the phase difference θc between the reference signal light RL and the monitor signal light ML may be continuously swept. Alternatively, the average optical power P _PD value of the interference signal light IL at two or more different phase differences θc may be measured simultaneously using an optical hybrid, and the vibration amplitude of the average optical power P _PD may be calculated from the measured value. Good. When the optical hybrid is used, sweeping of the phase difference θc can be made unnecessary.

In the case where monitoring the vibration amplitude of the average optical power P _PD of the interference signal light IL adjusting the phase bias α of the optical switch 1, the value of the phase difference θc of eye opening is maximum in the first phase of the device operation Need not be stored in the optical phase shifter 5.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 6 is a block diagram of an all-optical signal regeneration device including an optical switch adjustment circuit according to a third embodiment of the present invention. The present embodiment more specifically describes the first embodiment.
In the present embodiment, the optical switch 1 is turned on / off by the deteriorated signal light DL deteriorated by transmission. Other configurations and operations are exactly the same as those in the second embodiment, and thus description thereof is omitted.

  When the deteriorated signal light DL input to the optical switch 1 and the output signal light OUTL from the optical switch 1 have the same wavelength, the reference signal light RL is branched from the deteriorated signal light DL, and the reference signal light RL and the output are output. The interference signal light IL may be detected by superimposing the signal light OUTL.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. FIG. 7 is a block diagram of an OTDM (Optical Time Division Multiplexing) -DEMUX device including an optical switch adjustment circuit according to the fourth embodiment of the present invention. The present embodiment more specifically describes the first embodiment. The apparatus of the present embodiment shown in FIG. 7 is an OTDM-DEMUX apparatus that outputs any one of the optical signal time division multiplexed input signal light INL as an output signal light OUTL.

  The optical switch 1 is turned on / off according to the clock electrical signal CK, and data-modulates the input signal light INL that is OTDM signal light. Thereby, the optical switch 1 extracts a low bit rate signal corresponding to the clock frequency from the input signal light INL and outputs it as the output signal light OUTL. Other configurations and operations are exactly the same as those in the second embodiment, and thus description thereof is omitted.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described. FIG. 8 is a block diagram of an all-optical signal processing type OTDM (Optical Time Division Multiplexing) -DEMUX apparatus including an optical switch adjustment circuit according to a fifth embodiment of the present invention. The present embodiment more specifically describes the first embodiment.
The optical switch 1 is turned on / off in response to the clock signal light CKL, and data-modulates the input signal light INL, which is an OTDM signal light. Thereby, the optical switch 1 extracts a low bit rate signal corresponding to the clock frequency from the input signal light INL and outputs it as the output signal light OUTL. Other configurations and operations are exactly the same as those in the fourth embodiment, and a description thereof will be omitted.

  When the clock signal light CKL input to the optical switch 1 and the output signal light OUTL from the optical switch 1 have the same wavelength, the reference signal light RL is branched from the clock signal light CKL, and the reference signal light RL and the output are outputted. The interference signal light IL may be detected by superimposing the signal light OUTL.

[Sixth Embodiment]
Next, a sixth embodiment of the present invention will be described. FIG. 9 is a block diagram of an all-optical signal regeneration device including an optical switch adjustment circuit according to a sixth embodiment of the present invention. This embodiment more specifically describes the third embodiment.

  The all-optical signal regeneration device of this embodiment includes a distributor 10, a delay circuit 11, a symmetric Mach-Zehnder (SMZ) type all-optical switch 12, a bandpass filter (BPF) 19, an optical And a switch adjustment circuit 2a. The distributor 10, the delay circuit 11, the SMZ type all-optical switch 12, and the BPF 19 correspond to the optical switch 1 of the third embodiment.

  The distributor 10 branches the deteriorated signal light DL. The delay circuit 11 delays the deteriorated signal light DL output from the distributor 10. The SMZ type all-optical switch 12 receives the degraded signal light DL, the degraded signal light DL delayed by the delay circuit 11, and the input signal light INL. The input signal light INL in the present embodiment is clock light.

  The SMZ all-optical switch 12 is delayed by a splitter 13 that branches the input signal light INL, a multiplexer 14 that combines the input signal light INL and the degraded signal light DL, and the input signal light INL and the delay circuit 11. A combiner 15 for combining the degraded signal light DL, a semiconductor optical amplifier (SOA) 16 for amplifying the output light of the combiner 14, and the output light of the combiner 15 The SOA 17 and a linear phase shifter 18 that shifts the phase of the output light of the SOA 17 are configured. The linear phase shifter 18 adjusts the phase bias α of the SMZ type all-optical switch 12.

  The optical switch adjustment circuit 2a includes a distributor 3, a distributor 4, a delay circuit 20, an optical phase shifter 21, polarization controllers 22, 23, a 3 dB optical coupler 24, a photodiode (PD) 25, An A / D converter 26 and a CPU 27 are included. The polarization controllers 22 and 23 and the 3 dB optical coupler 24 correspond to the interference signal light generation unit of the third embodiment. The PD 25, the A / D converter 26, and the CPU 27 correspond to the photodetector 7 of the third embodiment. The CPU 27 corresponds to the phase bias adjustment unit 8 of the third embodiment.

  The delay circuit 20 delays the reference signal light RL from the distributor 3, and the optical phase shifter 21 shifts the phase of the reference signal light RL delayed by the delay circuit 20. The optical phase shifter 21 fixes the phase difference θc between the reference signal light RL and the monitor signal light ML at a certain value, like the optical phase shifter 5 of the third embodiment. Note that the delay by the delay circuit 20 is not an essential requirement.

  The 3 dB optical coupler 24 includes a reference signal light RL phase-shifted by the optical phase shifter 21 and adjusted in polarization by the polarization controller 22, and a monitor signal light ML output from the distributor 4 and adjusted in polarization by the polarization controller 23. To interfere with each other. Note that the polarization adjustment of light by the polarization controllers 22 and 23 is not an essential requirement.

The PD 25 photoelectrically converts the interference signal light IL from the 3 dB optical coupler 24. The A / D converter 26 A / D converts the output signal of the PD 25. The CPU 27 recognizes the average optical power P _PD of the interference signal light IL based on the data output from the A / D converter 26, and the phase of the linear phase shifter 18 so that the average optical power P _PD becomes maximum or minimum. Control the shift amount.

Thus, the eye opening of the output signal light OUTL can be automatically maximized, and the same effect as in the third embodiment can be obtained.
Regarding the phase difference θc between the reference signal light RL and the monitor signal light ML, the value of the phase difference θc that maximizes the eye opening is set in the optical phase shifter 21 in advance by the CPU 27 or manually during the initial operation. Just keep it.

Further, this embodiment can be used as an eye opening monitor circuit. In this case, CPU 27 measures the dependence of the average optical power P _PD of the interference signal light IL with respect to the phase difference θc between the optical reference signal RL and the monitor signal light ML. In dependence of the average optical power P _PD of the interference signal light IL with respect to the phase difference θc it is known, as is clear from the description of FIG. 3 (A), the can be calculated back phase bias α of the optical switch 1. The CPU 27 derives the eye opening or output light extinction ratio of the output signal light OUTL from the calculated value of the phase bias α, and displays the eye opening or output light extinction ratio on a display unit (not shown). As shown in FIG. 2, if the relationship between the phase bias α and the eye opening or output light extinction ratio is known, the eye opening or output light extinction ratio can be derived from the value of the phase bias α.

[Seventh Embodiment]
Next, a seventh embodiment of the present invention will be described. FIG. 10 is a block diagram of an all-optical signal regeneration device including an optical switch adjustment circuit according to a seventh embodiment of the present invention. This embodiment more specifically describes the third embodiment. The input signal light INL in the present embodiment is clock light.
The all-optical signal regeneration device of this embodiment includes a distributor 10, a delay circuit 11, an SMZ type all-optical switch 12, a BPF 19, and an optical switch adjustment circuit 2b. The configuration of the SMZ all-optical switch 12 is the same as that of the sixth embodiment.

  The optical switch adjustment circuit 2b includes a distributor 3, a distributor 4, a delay circuit 20, an optical phase shifter 21b, polarization controllers 22 and 23, a 3 dB optical coupler 24, a PD 25, and an A / D converter 26. And a CPU 27b, a low-frequency oscillator 28, and a high-pass filter 29.

In the present embodiment, the optical phase shifter 21b sweeps the phase difference θc between the reference signal light RL and the monitor signal light ML at a low frequency corresponding to the signal output from the low frequency oscillator 28. The high pass filter 29 removes the DC component of the output signal of the PD 25. Lower cutoff frequency of the high pass filter 29 is lower than the low-frequency frequency of the average optical power P _PD of the interference signal light IL.

CPU27b recognizes the vibration amplitude of the average optical power P _PD of the interference signal light IL on the basis of the output data from the A / D converter 26, a phase shift amount of the linear phase shifter 18 as the vibration amplitude is minimum To control. The operation of the other configuration is as described in the sixth embodiment.

Thus, the eye opening of the output signal light OUTL can be automatically maximized, and the same effect as in the third embodiment can be obtained.
In the case of the present embodiment, it is not necessary to set a specific value of the phase difference θc between the reference signal light RL and the monitor signal light ML in the optical phase shifter 21b during the initial operation.

[Eighth Embodiment]
Next, an eighth embodiment of the present invention will be described. FIG. 11 is a block diagram of an all-optical signal regeneration device including an optical switch adjustment circuit according to an eighth embodiment of the present invention. This embodiment more specifically describes the third embodiment. The input signal light INL in the present embodiment is clock light.
The all-optical signal regeneration device of the present embodiment includes a distributor 10, a delay circuit 11, an SMZ type all-optical switch 12, a BPF 19, and an optical switch adjustment circuit 2c. The configuration of the SMZ all-optical switch 12 is the same as that of the sixth embodiment.

  The optical switch adjustment circuit 2c includes a distributor 3, a distributor 4, a delay circuit 20, an optical phase shifter 21, polarization controllers 22, 23, a PD 25c, an A / D converter 26c, a CPU 27c, The hybrid 30 is configured.

  In the present embodiment, the reference signal light RL phase-shifted by the optical phase shifter 21 and adjusted in polarization by the polarization controller 22 and the monitor signal light ML output from the distributor 4 and adjusted in polarization by the polarization controller 23 are used. The optical hybrid 30 is used when superimposing the two. The optical hybrid 30 outputs a plurality of interference signal lights IL having different phase differences θc.

The plurality of PDs 25c photoelectrically convert each interference signal light IL having a different phase difference. The A / D converter 26c performs A / D conversion on the output signal of each PD 25. CPU27c recognizes the average optical power P _PD of the phase difference θc based on a plurality of data output from the A / D converter 26c is different interference signal light IL, the average optical power P _PD of the interference signal light IL The phase shift amount of the linear phase shifter 18 is controlled so as to be maximized or minimized. In this case, it suffices to average optical power P _PD of any one of the interference signal light IL of the plurality of interference signal light IL is maximum or minimum. The operation of the other configuration is as described in the sixth embodiment.

In this embodiment, since the phase difference θc adjusts the phase bias α of SMZ all-optical switch 12 based on the average optical power P _PD of different interference signal light IL, as compared to the sixth embodiment Controllability, sensitivity, and stability can be improved.

Incidentally, CPU27c recognizes the average optical power P _PD of the phase difference θc based on a plurality of data output from the A / D converter 26c is different interference signal light IL, the average optical power P of the interference signal light IL The vibration amplitude of the _PD may be calculated and the phase shift amount of the linear phase shifter 18 may be controlled so that the vibration amplitude is minimized. As described above, when the optical hybrid 30 is used, an interference signal with respect to the phase difference θc between the reference signal light RL and the monitor signal light ML without sweeping out the phase difference θc between the reference signal light RL and the monitor signal light ML. it is possible to calculate the vibration amplitude of the average optical power P _PD light IL.

  In the sixth to eighth embodiments, a symmetric Mach-Zehnder all-optical switch (SMZ) is used as an optical switch, but there is no problem even if it is replaced with another optical switch.

  The present invention can be applied to an adjustment circuit of an optical switch.

  DESCRIPTION OF SYMBOLS 1 ... Optical switch, 2, 2a, 2b, 2c ... Optical switch adjustment circuit, 3, 4, 10, 13 ... Divider, 5, 21, 21b ... Optical phase shifter, 6 ... Interference signal light generation part, 7 ... Light Detector: 8 ... Phase bias adjustment unit, 11, 20 ... Delay circuit, 12 ... Symmetric Mach-Zehnder all-optical switch, 14, 15 ... Multiplexer, 16, 17 ... Semiconductor optical amplifier, 18 ... Linear phase shifter, 19 ... band pass filter, 22, 23 ... polarization controller, 24 ... 3dB optical coupler, 25, 25c ... photodiode, 26, 26c ... A / D converter, 27, 27b, 27c ... CPU, 28 ... low frequency oscillator, 29 ... high-pass filter, 30 ... optical hybrid.

Claims (12)

First distribution means for branching the signal light input to the optical switch and outputting it as reference signal light;
Second distribution means for branching the output signal light from the optical switch and outputting it as monitor signal light;
A phase shifter for shifting the phase relationship between the reference signal light and the monitor signal light;
Interference signal light generation means for causing the reference signal light phase-shifted by the optical phase shifter and the monitor signal light output from the second distribution means to overlap and interfere,
A photodetector for detecting the power of the interference signal light output from the interference signal light generation means;
Phase bias adjusting means for feeding back to the optical switch a phase bias condition that maximizes the eye opening of the output signal light in accordance with a time average value of the optical power detected by the photodetector. Optical switch adjustment circuit. The optical switch adjustment circuit according to claim 1,
The phase shifter fixes a phase difference between the reference signal light and the monitor signal light to a predetermined value,
The optical switch adjustment circuit, wherein the phase bias adjustment means adjusts the phase bias of the optical switch so that the time average power of the interference signal light detected by the photodetector is maximized or minimized. The optical switch adjustment circuit according to claim 2,
The interference signal light generation means is an optical hybrid that outputs a plurality of interference signal lights having different phase differences between the reference signal light and the monitor signal light,
The photodetector detects the power of each of a plurality of interference signal lights,
The phase switch adjuster adjusts the phase bias of the optical switch so that the time average power of any one of the plurality of interference signal lights is maximized or minimized. Adjustment circuit. The optical switch adjustment circuit according to claim 1,
The optical switch adjustment circuit, wherein the phase bias adjustment means adjusts the phase bias of the optical switch so that the vibration amplitude of the time average power of the interference signal light detected by the photodetector is minimized. The optical switch adjustment circuit according to claim 4, wherein
The optical switch adjustment circuit, wherein the phase shifter sweeps a phase difference between the reference signal light and the monitor signal light. The optical switch adjustment circuit according to claim 4, wherein
The interference signal light generation means is an optical hybrid that outputs a plurality of interference signal lights having different phase differences between the reference signal light and the monitor signal light,
The phase bias adjusting means obtains the vibration amplitude of the time average power based on the time average power of the plurality of interference signal lights, and adjusts the phase bias of the optical switch so that the vibration amplitude is minimized. Optical switch adjustment circuit. In the optical switch adjustment circuit according to any one of claims 4 to 6,
The optical switch adjustment circuit further comprises a high-pass filter between the photodetector and the phase bias adjustment means. First distribution means for branching the signal light input to the optical switch and outputting it as reference signal light;
Second distribution means for branching the output signal light from the optical switch and outputting it as monitor signal light;
A phase shifter for shifting the phase relationship between the reference signal light and the monitor signal light;
Interference signal light generation means for causing the reference signal light phase-shifted by the optical phase shifter and the monitor signal light output from the second distribution means to overlap and interfere,
A photodetector for detecting the power of the interference signal light output from the interference signal light generation means;
The dependence of the time average power of the interference signal light detected by the photodetector on the phase difference due to the phase shifter is measured, the phase bias value of the optical switch is calculated from the measurement result, and the calculated phase bias is calculated. An eye opening monitor circuit comprising: calculation means for deriving an eye opening or an output light extinction ratio of the output signal light from a value. An optical switch,
An optical signal transmitter comprising: the optical switch adjustment circuit according to claim 2. An optical switch,
An all-optical signal regeneration device comprising the optical switch adjustment circuit according to claim 2. An optical switch,
An OTDM-DEMUX apparatus comprising the optical switch adjustment circuit according to claim 2. A first distribution procedure for branching signal light input to the optical switch into reference signal light;
A second distribution procedure for branching the output signal light from the optical switch into monitor signal light;
A phase shift procedure for shifting the phase relationship between the reference signal light and the monitor signal light;
An interference signal light generation procedure in which the phase-shifted reference signal light and the monitor signal light obtained in the second distribution procedure are overlapped to interfere with each other;
A detection procedure for detecting the power of the interference signal light obtained in this interference signal light generation procedure;
A phase bias adjustment procedure for feeding back to the optical switch a phase bias condition that maximizes the eye opening of the output signal light according to the time average value of the optical power detected by the detection procedure. Optical switch adjustment method.