WO2014097503A1 - 光変調器、光送信器、光送受信システム及び光変調器の制御方法 - Google Patents
光変調器、光送信器、光送受信システム及び光変調器の制御方法 Download PDFInfo
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- WO2014097503A1 WO2014097503A1 PCT/JP2013/004352 JP2013004352W WO2014097503A1 WO 2014097503 A1 WO2014097503 A1 WO 2014097503A1 JP 2013004352 W JP2013004352 W JP 2013004352W WO 2014097503 A1 WO2014097503 A1 WO 2014097503A1
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/0121—Operation of devices; Circuit arrangements, not otherwise provided for in this subclass
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/548—Phase or frequency modulation
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/011—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour in optical waveguides, not otherwise provided for in this subclass
Definitions
- the present invention relates to an optical modulator, an optical transmitter, an optical transmission / reception system, and an optical modulator control method.
- wavelength-division-multiplexed optical fiber communication systems With the explosive demand for broadband multimedia communication services such as the Internet and video distribution, long-distance, large-capacity and high-reliability high-density wavelength-division-multiplexed optical fiber communication systems are being introduced in trunk lines and metro lines.
- optical fiber access services are rapidly spreading in subscriber systems.
- it is important to reduce the installation cost of an optical fiber that is an optical transmission line and to increase the transmission band utilization efficiency per optical fiber. For this reason, a wavelength multiplexing technique that multiplexes and transmits optical signals having different wavelengths is widely used.
- Optical transmitters for WDM optical fiber communication systems are capable of high-speed optical modulation, have small optical signal wavelength dependency, and unnecessary optical phase modulation components (modulation) that cause deterioration of the received optical waveform during long-distance signal transmission
- an optical modulator in which the light intensity modulation component (when the method is a light intensity modulation method) or the light intensity modulation component (when the modulation method is an optical phase modulation method) is minimized.
- an MZ light intensity modulator incorporating an optical waveguide type optical phase modulator similar to an optical waveguide type Mach-Zehnder (hereinafter, MZ) interferometer is practical.
- the optical modulation spectrum is higher than that of the normal binary light intensity modulation method.
- a multilevel optical modulation signaling scheme with a narrower bandwidth is advantageous. This multi-level optical modulation signal system is considered to become mainstream particularly in a trunk optical fiber communication system exceeding 40 Gb / s, where future demand is expected to increase.
- a monolithic integrated multilevel IQ optical modulator combining the two MZ optical intensity modulators described above and an optical multiplexer / demultiplexer has been developed for such applications.
- the length of the electrode provided in the optical phase modulator region of the optical modulator is set.
- the propagation wavelength of the modulated electric signal is shortened to a level that cannot be ignored.
- the potential distribution of the electrode structure which is a means for applying an electric field to the optical phase modulator, cannot be regarded as uniform in the optical signal propagation axis direction. Therefore, in order to accurately estimate the light modulation characteristics, it is necessary to treat the electrode itself as a distributed constant line and a modulated electric signal propagating through the optical phase modulator region as a traveling wave.
- phase velocity vo of the modulated optical signal and the phase velocity vm of the modulated electrical signal are made as close as possible (phase velocity).
- a so-called traveling wave type electrode structure is required which is devised.
- An optical modulator module having a split electrode structure for realizing such a traveling wave electrode structure and a multilevel optical modulation signal system has already been proposed (Patent Documents 1 to 4).
- an optical modulator module capable of multilevel control of the phase change of the modulated optical signal in each of the divided electrodes is a compact, wideband, and capable of generating an arbitrary multilevel optical modulation signal by inputting a digital signal while maintaining phase velocity matching and impedance matching required for traveling wave structure operation.
- JP 7-13112 A Japanese Patent Laid-Open No. 5-289033 JP-A-5-257102 International Publication No. 2011/043079
- the inventor has found that the above-described optical modulator module has the following problems.
- a plurality of drivers for driving the divided electrodes are required.
- it is necessary to supply power to the plurality of drivers.
- power consumption by a plurality of drivers increases.
- the number of divided electrodes increases, and the number of drivers increases accordingly. In this case, the increase in power consumption becomes particularly significant.
- the present invention has been made in view of the above problems, and an object of the present invention is to reduce the power consumption of an optical transmitter having a split electrode structure.
- An optical modulator includes: an optical modulation unit that includes a plurality of phase modulation regions formed on an optical waveguide, outputs an optical signal obtained by binary-modulating input light; and the plurality of phase modulation regions.
- a driving circuit having a plurality of drivers for outputting a driving signal corresponding to an input digital signal; a determination circuit for determining a driver to be activated among the plurality of drivers based on information indicating a transmission rate; and the determination circuit
- a driver control circuit that activates a driver specified by the determination result of the driver and shuts off a power supply of a driver other than the activated driver, and a switching circuit that switches connections between the plurality of drivers and the plurality of phase modulation regions; And a switching control circuit that controls the switching circuit so that the drive signal is applied to the plurality of phase modulation regions from the activated driver.
- An optical transmitter includes: a light modulation unit that outputs a light signal obtained by binary-modulating input light; and a light source that outputs the input light. And a drive circuit having a plurality of drivers for outputting a drive signal corresponding to an input digital signal to the plurality of phase modulation regions, and a driver to be activated among the plurality of drivers based on information indicating a transmission rate
- An optical transmission / reception system that is one embodiment of the present invention includes an optical transmitter that outputs an optical signal and an optical receiver that receives the optical signal, and the optical transmitter has a plurality of phases on an optical waveguide.
- a modulation region is formed, an optical modulation unit that outputs the optical signal obtained by binary modulation of input light, a light source that outputs the input light, and a drive signal corresponding to the input digital signal is output to the plurality of phase modulation regions
- a driver circuit having a plurality of drivers, a determination circuit for determining a driver to be activated among the plurality of drivers based on information indicating a transmission rate, and a driver specified by a determination result in the determination circuit being activated
- a driver control circuit that shuts off the power supply of drivers other than the activated driver, a switching circuit that switches connections between the plurality of drivers and the plurality of phase modulation regions, and the activated driver As the driving signals to the plurality of the phase modulation region from bar is applied, in which and a switching control circuit
- An optical modulator control method is based on information indicating a transmission rate, and an input digital signal is input to a plurality of phase modulation regions provided on the optical waveguide that modulates input light propagating through the optical waveguide.
- the driver to be activated is determined from among a plurality of drivers that output a drive signal corresponding to the signal, the driver designated by the determination is activated, the power of drivers other than the activated driver is shut off, and the activation is performed.
- the connection between the plurality of drivers and the plurality of phase modulation regions is switched so that the drive signal is applied to the plurality of phase modulation regions from the driver.
- the power consumption of an optical transmitter having a split electrode structure can be reduced.
- FIG. 6 is a diagram schematically showing a configuration of an optical multiplexer / demultiplexer 613.
- FIG. 6 is a diagram schematically showing a configuration of an optical multiplexer / demultiplexer 614.
- 5 is an operation table showing the operation of the optical modulator 600.
- FIG. 6 is a diagram schematically showing a light propagation mode in the optical modulator 600.
- FIG. 11 is a constellation diagram showing lights L1 and L2 when phase modulation is not performed by the phase modulation regions PM61_1 to PM61_7 and the phase modulation regions PM62_1 to PM62_7.
- FIG. 10 is a constellation diagram showing the lights L1 and L2 when the binary code of the input digital signal is “000” in the optical modulator 600.
- 4 is a constellation diagram showing light L1 and L2 in the optical modulator 600.
- FIG. 1 is a block diagram schematically showing a configuration of an optical transmitter 1000 according to a first embodiment.
- 1 is a plan view schematically showing a configuration of an optical modulator 100 according to a first embodiment. It is an equivalent circuit diagram in the case where a pin structure diode behaves as a capacitive load.
- FIG. 4 is a graph showing a required transmission rate and band characteristics of the optical modulator 100.
- 5 is a flowchart illustrating a method for determining an activation driver of the optical modulator 100. It is a top view which shows the optical modulator 100 when a request
- FIG. FIG. 6 is a plan view schematically showing a configuration of an optical modulator 200 according to a second embodiment.
- 5 is a flowchart illustrating a method for determining an activation driver of the optical modulator 200.
- FIG. 1 is a block diagram schematically showing a configuration of a multi-value optical transmitter 6000 having a general divided electrode structure.
- the optical transmitter 6000 includes a light source 6001 and an optical modulator 600.
- the light source 6001 typically uses a laser diode, and outputs CW (Continuous Wave) light 6002 to the optical modulator 600, for example.
- the optical modulator 600 is a 3-bit optical modulator.
- the optical modulator 600 modulates the input CW light 6002 according to the input digital signal D [2: 0], which is a 3-bit digital signal, and outputs a 3-bit optical signal 6003.
- FIG. 2 is a plan view schematically showing the configuration of the optical modulator 600.
- the optical modulator 600 includes an optical modulation unit 61, a decoding unit 62, and a drive circuit 63.
- the light modulator 61 outputs an optical signal OUT obtained by modulating the input light IN.
- the input light IN corresponds to the CW light 6002 in FIG.
- the optical signal OUT corresponds to the optical signal 6003 in FIG.
- the optical modulator 61 includes optical waveguides 611 and 612, optical multiplexers / demultiplexers 613 and 614, phase modulation regions PM61_1 to PM61_7, and PM62_1 to PM62_7.
- the optical waveguides 611 and 612 are arranged in parallel.
- An optical multiplexer / demultiplexer 613 is inserted on the optical input (input light IN) side of the optical waveguides 611 and 612.
- the input light IN is input to the input port P1, and the input port P2 is not input.
- the optical waveguide 611 is connected to the output port P3, and the optical waveguide 612 is connected to the output port P4.
- FIG. 3A is a diagram schematically showing the configuration of the optical multiplexer / demultiplexer 613.
- the light incident on the input port P1 propagates to the output ports P3 and P4.
- the phase of light propagating from the input port P1 to the output port P4 is delayed by 90 ° compared to the light propagating from the input port P1 to the output port P3.
- the light incident on the input port P2 propagates to the output ports P3 and P4.
- the phase of light propagating from the input port P2 to the output port P3 is delayed by 90 ° compared to the light propagating from the input port P2 to the output port P4.
- An optical multiplexer / demultiplexer 614 is inserted on the optical signal output (optical signal OUT) side of the optical waveguides 611 and 612.
- the optical waveguide 611 is connected to the input port P5
- the optical waveguide 612 is connected to the input port P6.
- the optical signal OUT is output from the output port P7.
- FIG. 3B is a diagram schematically showing the configuration of the optical multiplexer / demultiplexer 614.
- the optical multiplexer / demultiplexer 614 has the same configuration as the optical multiplexer / demultiplexer 613.
- the input ports P5 and P6 correspond to the input ports P1 and P2 of the optical multiplexer / demultiplexer 613, respectively.
- the output ports P7 and P8 correspond to the output ports P3 and P4 of the optical multiplexer / demultiplexer 613, respectively.
- the light incident on the input port P5 propagates to the output ports P7 and P8.
- phase of light propagating from the input port P5 to the output port P8 is delayed by 90 ° compared to the light propagating from the input port P5 to the output port P7.
- the light incident on the input port P6 propagates to the output ports P7 and P8.
- the phase of light propagating from the input port P6 to the output port P7 is delayed by 90 ° compared to the light propagating from the input port P6 to the output port P8.
- Phase modulation regions PM61_1 to PM61_7 are arranged in the optical waveguide 611 between the optical multiplexer / demultiplexer 613 and the optical multiplexer / demultiplexer 614.
- Phase modulation regions PM62_1 to PM62_7 are arranged in the optical waveguide 612 between the optical multiplexer / demultiplexer 613 and the optical multiplexer / demultiplexer 614.
- the phase modulation region is a region having electrodes formed on the optical waveguide.
- an electric signal for example, a voltage signal
- the effective refractive index of the optical waveguide under the electrode changes.
- the substantial optical path length of the optical waveguide in the phase modulation region can be changed.
- the phase modulation region can change the phase of the optical signal propagating through the optical waveguide.
- the optical signal can be modulated by giving a phase difference between the optical signals propagating between the two optical waveguides 611 and 612. That is, the light modulator 61 constitutes a multi-value Mach-Zehnder light modulator having two arms and an electrode division structure.
- the decode unit 62 decodes the 3-bit input digital signal D [2: 0] and outputs, for example, multi-bit signals D1 to D7 to the drive circuit 63.
- the drive circuit 63 has binary drivers DR61 to DR67. Signals D1 to D7 are supplied to the drivers DR61 to DR67, respectively. Drivers DR61 to DR67 output a pair of differential output signals in accordance with signals D1 to D7. At this time, the positive-phase output signals of the differential output signals output from the drivers DR61 to DR67 are output to the phase modulation regions PM61_1 to PM61_7. Respective negative phase output signals of the differential output signals output from the drivers DR61 to DR67 are output to the phase modulation areas PM62_1 to PM62_7.
- the drivers DR61 to DR67 are binary output (0, 1) drivers as described above. That is, the drivers DR61 to DR67 output “0” or “1” as the positive phase output signal according to the values of the signals D1 to D7.
- the drivers DR61 to DR67 output a signal obtained by inverting the normal phase output signal as a negative phase output signal. That is, the drivers DR61 to DR67 output “1” or “0” as the reverse phase output signal according to the values of the signals D1 to D7.
- FIG. 4 is an operation table showing the operation of the optical modulator 600.
- the driver DR61 When the input digital signal D [2: 0] is “000”, the driver DR61 outputs “0” as the normal phase output signal and “1” as the negative phase output signal.
- the driver DR61 When the input digital signal D [2: 0] is “001” or more, the driver DR61 outputs “1” as the normal phase output signal and “0” as the negative phase output signal.
- the driver DR62 When the input digital signal D [2: 0] is “001” or less, the driver DR62 outputs “0” as the normal phase output signal and “1” as the negative phase output signal. When the input digital signal D [2: 0] is “010” or more, the driver DR62 outputs “1” as the normal phase output signal and “0” as the negative phase output signal.
- the driver DR63 When the input digital signal D [2: 0] is “010” or less, the driver DR63 outputs “0” as the normal phase output signal and “1” as the negative phase output signal. When the input digital signal D [2: 0] is “011” or more, the driver DR63 outputs “1” as the normal phase output signal and “0” as the negative phase output signal.
- the driver DR64 When the input digital signal D [2: 0] is “011” or less, the driver DR64 outputs “0” as the normal phase output signal and “1” as the negative phase output signal. When the input digital signal D [2: 0] is “100” or more, the driver DR64 outputs “1” as the normal phase output signal and “0” as the negative phase output signal.
- the driver DR65 When the input digital signal D [2: 0] is “100” or less, the driver DR65 outputs “0” as the normal phase output signal and “1” as the negative phase output signal. When the input digital signal D [2: 0] is “101” or more, the driver DR65 outputs “1” as the normal phase output signal and “0” as the negative phase output signal.
- the driver DR66 When the input digital signal D [2: 0] is “101” or less, the driver DR66 outputs “0” as the normal phase output signal and “1” as the negative phase output signal. When the input digital signal D [2: 0] is “110” or more, the driver DR66 outputs “1” as the normal phase output signal and “0” as the negative phase output signal.
- the driver DR67 When the input digital signal D [2: 0] is “110” or less, the driver DR67 outputs “0” as the normal phase output signal and “1” as the negative phase output signal. When the input digital signal D [2: 0] is “111”, the driver DR67 outputs “1” as the normal phase output signal and “0” as the negative phase output signal.
- FIG. 5 is a diagram schematically illustrating a light propagation mode in the optical modulator 600.
- the input light IN is input to the input port P ⁇ b> 1 of the optical multiplexer / demultiplexer 613. Therefore, the phase of the light output from the output port P4 is delayed by 90 ° compared to the light output from the output port P3. Thereafter, the light output from the output port P3 passes through the phase modulation regions PM61_1 to PM61_7 and reaches the input port P5 of the optical multiplexer / demultiplexer 614. The light that reaches the input port P5 reaches the output port P7 as it is.
- the light output from the output port P4 passes through the phase modulation regions PM62_1 to PM62_7 and reaches the input port P6 of the optical multiplexer / demultiplexer 614.
- the light reaching the input port P6 reaches the output port P7 with a phase delay of 90 °.
- the phase modulation regions PM61_1 to PM61_7 and the phase modulation regions PM62_1 to PM62_7 are not subjected to phase modulation, the light L2 reaching the output port P7 from the input port P6 is the light reaching the output port P7 from the input port P5. Compared to L1, the phase is delayed by 180 °.
- FIG. 6A is a constellation diagram showing the lights L1 and L2 when the phase modulation regions PM61_1 to PM61_7 and the phase modulation regions PM62_1 to PM62_7 are not subjected to phase modulation.
- the phase of the light L2 reaching the output port P7 from the input port P6 is delayed by 180 ° compared to the light L1 reaching the output port P7 from the input port P5.
- the positive phase output signal is input to the phase modulation regions PM61_1 to PM61_7, and the negative phase output signal is input to the phase modulation regions PM62_1 to PM62_7.
- the phase delay of the light L2 reaching the output port P7 from the input port P6 is compensated.
- FIG. 6B is a constellation diagram showing the lights L1 and L2 when the binary code of the input digital signal D [2: 0] is “000” in the optical modulator 600.
- FIG. For example, if the binary code of the input digital signal D [2: 0] is “111”, a positive phase output signal “1” is input to the phase modulation regions PM61_1 to PM61_7. On the other hand, “0” that is an antiphase output signal is input to the phase modulation regions PM62_1 to PM62_7. As a result, the phase of the light passing through the phase modulation areas PM62_1 to PM62_7 is further delayed by 180 °.
- the light L2 reaching the output port P7 from the input port P6 is added with 180 ° which is the phase delay due to the phase modulation regions PM62_1 to PM62_7 in addition to the original 180 ° phase delay.
- a 360 ° phase lag occurs in the light L2 reaching the output port P7 from the input port P6, so that the phase lag with respect to the light L1 reaching the output port P7 from the input port P5 is substantially eliminated.
- FIG. 6C is a constellation diagram showing the lights L1 and L2 in the optical modulator 600.
- the phase modulation amount of the light L1 is 0 to 7 ⁇ and the phase modulation amount of the light L2 is 0 to ⁇ 7 ⁇ according to the value of the input digital signal D [3: 0]. It can be changed in 8 stages.
- the optical transmitter 1000 is an optical transmitter that performs a binary (ie, 1-bit) modulation operation.
- FIG. 7 is a block diagram schematically illustrating a configuration of the optical transmitter 1000 according to the first embodiment.
- the optical transmitter 1000 includes a light source 1001 and an optical modulator 100.
- the light source 1001 typically uses a laser diode, and outputs CW (Continuous Wave) light 1002 to the optical modulator 100, for example.
- the optical modulator 100 is a binary (1 bit) optical modulator.
- the optical modulator 100 modulates the input CW light 1002 according to the input digital signal DIN that is a binary digital signal, and outputs a binary optical signal 1003.
- FIG. 8 is a plan view schematically showing the configuration of the optical modulator 100 according to the first embodiment.
- the optical modulator 100 includes an optical modulator 11, a drive circuit 12, a determination circuit 13, a driver control circuit 14, a driver output switching circuit 15, and a switching control circuit 16.
- the optical modulation unit 11 includes optical waveguides 111 and 112, optical multiplexers / demultiplexers 113 and 114, and phase modulation regions PM1_1 to PM1_7 and PM2_1 to PM2_7.
- the optical waveguides 111 and 112 correspond to the first and second optical waveguides, respectively.
- the optical multiplexer / demultiplexers 113 and 114 correspond to the first and second optical multiplexer / demultiplexers, respectively.
- the phase modulation areas PM1_1 to PM1_7 correspond to the first phase modulation area.
- the phase modulation areas PM2_1 to PM2_7 correspond to the second phase modulation area.
- the optical modulation unit 11 has a so-called Mach-Zehnder optical resonator structure in which split electrodes (phase modulation regions PM1_1 to PM1_7, PM2_1 to PM2_7) are arranged on two optical waveguides (optical waveguides 111 and 112). .
- the optical waveguides 111 and 112 are arranged in parallel.
- An optical multiplexer / demultiplexer 113 is inserted on the optical signal input (input light IN) side of the optical waveguides 111 and 112.
- the optical multiplexer / demultiplexer 113 has the same configuration as the optical multiplexer / demultiplexer 613 described above.
- the input light IN is input to the input port P1, and the input port P2 is not input.
- the optical waveguide 111 is connected to the output port P3, and the optical waveguide 112 is connected to the output port P4.
- the input light IN corresponds to the CW light 1002 in FIG.
- An optical multiplexer / demultiplexer 114 is inserted on the optical signal output (optical signal OUT) side of the optical waveguides 111 and 112.
- the optical multiplexer / demultiplexer 114 has the same configuration as the optical multiplexer / demultiplexer 614 described above.
- the optical waveguide 111 is connected to the input port P5
- the optical waveguide 112 is connected to the input port P6.
- the optical signal OUT is output from the output port P7.
- the optical signal OUT corresponds to the optical signal 1003 in FIG.
- phase modulation regions PM1_1 to PM1_7 are arranged in the optical waveguide 112 between the optical multiplexer / demultiplexer 113 and the optical multiplexer / demultiplexer 114.
- the phase modulation region is a region having one electrode (divided electrode) formed on the optical waveguide.
- an electric signal for example, a voltage signal
- the effective refractive index of the optical waveguide under the electrode changes.
- the substantial optical path length of the optical waveguide in the phase modulation region can be changed.
- the phase modulation region can change the phase of the optical signal propagating through the optical waveguide.
- the optical signal can be modulated by providing a phase difference between the optical signals propagating between the two optical waveguides 111 and 112. That is, the light modulator 11 constitutes a binary Mach-Zehnder light modulator having two arms and an electrode division structure.
- the drive circuit 12 has drivers 121 to 127. Each of the drivers 121 to 127 outputs a differential signal as a drive signal to the target phase modulation region in accordance with the binary input digital signal DIN. Specifically, the driver 121 outputs a normal phase drive signal via the switch S11 and outputs a reverse phase drive signal via the switch S12. The driver 122 outputs a normal phase drive signal via the switch S21 and outputs a negative phase drive signal via the switch S22. The driver 123 outputs a normal phase drive signal via the switch S31 and outputs a negative phase drive signal via the switch S32. The driver 124 outputs a normal phase drive signal via the switch S41 and outputs a negative phase drive signal via the switch S42.
- the driver 125 outputs a normal phase drive signal via the switch S51 and outputs a negative phase drive signal via the switch S52.
- the driver 126 outputs a normal phase drive signal via the switch S61, and outputs a negative phase drive signal via the switch S62.
- the driver 127 outputs a normal phase drive signal via the switch S71 and outputs a negative phase drive signal via the switch S72.
- the determination circuit 13 determines the number of drivers 121 to 127 to be activated from the required transmission rate information INF input from the outside.
- the determination circuit 13 outputs a signal SIG1 designating a driver to be activated to the driver control circuit 14 and the switching control circuit 16.
- the driver control circuit 14 activates the driver specified by the signal SIG1. Then, the driver control circuit 14 cuts off the power supply to the driver that is not specified by the signal SIG1.
- the driver output switching circuit 15 is a circuit that receives the control signal from the switching control circuit 16 and connects the activation driver designated by the signal SIG1 and each phase modulation region.
- the driver output switching circuit 15 has a plurality of switches.
- a switch S11 is inserted between the driver 121 and the phase modulation region PM1_1.
- a switch S21 is inserted between the driver 122 and the phase modulation region PM1_2.
- a switch S31 is inserted between the driver 123 and the phase modulation region PM1_3.
- a switch S41 is inserted between the driver 124 and the phase modulation region PM1_4.
- a switch S51 is inserted between the driver 125 and the phase modulation region PM1_5.
- a switch S61 is inserted between the driver 126 and the phase modulation region PM1_6.
- a switch S71 is inserted between the driver 127 and the phase modulation region PM1_7.
- Switch S12 is inserted between driver 121 and phase modulation area PM2_1.
- a switch S22 is inserted between the driver 122 and the phase modulation region PM2_2.
- a switch S32 is inserted between the driver 123 and the phase modulation region PM2_3.
- a switch S42 is inserted between the driver 124 and the phase modulation region PM2_4.
- a switch S52 is inserted between the driver 125 and the phase modulation region PM2_5.
- a switch S62 is inserted between the driver 126 and the phase modulation region PM2_6.
- a switch S72 is inserted between the driver 127 and the phase modulation region PM2_7.
- a switch B11 is inserted between the terminal of the switch S11 on the light modulation unit 11 side and the terminal of the switch S21 on the light modulation unit 11 side.
- a switch B21 is inserted between the light modulation unit 11 side terminal of the switch S21 and the light modulation unit 11 side terminal of the switch S31.
- a switch B31 is inserted between the light modulation unit 11 side terminal of the switch S31 and the light modulation unit 11 side terminal of the switch S41.
- a switch B41 is inserted between the terminal of the switch S41 on the light modulation unit 11 side and the terminal of the switch S51 on the light modulation unit 11 side.
- the switch B51 is inserted between the terminal of the switch S51 on the light modulation unit 11 side and the terminal of the switch S61 on the light modulation unit 11 side.
- a switch B61 is inserted between the light modulation unit 11 side terminal of the switch S61 and the light modulation unit 11 side terminal of the switch S71.
- a switch B12 is inserted between the terminal of the switch S12 on the light modulation unit 11 side and the terminal of the switch S22 on the light modulation unit 11 side.
- a switch B22 is inserted between the light modulation unit 11 side terminal of the switch S22 and the light modulation unit 11 side terminal of the switch S32.
- a switch B32 is inserted between the terminal of the switch S32 on the light modulation unit 11 side and the terminal of the switch S42 on the light modulation unit 11 side.
- the switch B42 is inserted between the terminal of the switch S42 on the light modulation unit 11 side and the terminal of the switch S52 on the light modulation unit 11 side.
- a switch B52 is inserted between the terminal of the switch S52 on the light modulation unit 11 side and the terminal of the switch S62 on the light modulation unit 11 side.
- a switch B62 is inserted between the terminal of the switch S62 on the light modulation unit 11 side and the terminal of the switch S72 on the light modulation unit 11 side.
- each switch of the driver output switching circuit 15 is controlled by a control signal from the switching control circuit 16.
- the switching control circuit 16 controls switching of the connection in the driver output switching circuit 15 between the activation driver designated by the signal SIG2 and each phase modulation area.
- the optical modulator 100 changes the driver to be activated according to the change in the transmission rate.
- a method for changing the activation driver of the optical modulator 100 will be described.
- the phase modulation region of the optical modulator 100 constitutes a diode having a pin (p-intrinsic-n) structure.
- the pin structure diode behaves as a capacitive load.
- FIG. 9 is an equivalent circuit diagram in the case where the pin structure diode behaves as a capacitive load.
- the driver and the pin structure diode 1 constitute an RC series circuit.
- the capacitance value C has a more dominant influence than the resistance value R.
- each driver may drive a pair of phase modulation regions.
- each driver has a band characteristic corresponding to the high required rate.
- the required transmission rate is low, there is a margin in the bandwidth characteristics of the driver.
- a plurality of phase modulation areas are driven per driver. In other words, the lower the required transmission rate, the fewer drivers are activated.
- FIG. 10 is a graph showing the required transmission rate and the band characteristics of the optical modulator 100.
- FIG. 10 shows the band characteristics of the optical modulator 100 when one driver drives a pair of phase variable regions.
- the required transmission rate is f1
- f2 is smaller than the upper limit of the band characteristics of the optical modulator 100. Therefore, even if one driver drives a plurality of pairs of phase variable regions, the required transmission is performed. It can correspond to the rate f2.
- the optical modulator 100 changes the number of drivers to be used according to the transmission rate. Specifically, the optical modulator 100 modulates an optical signal with an activated driver, deactivates a driver that is not used for modulation, and stops power supply.
- the activation of the driver refers to supplying power to the driver and outputting a drive signal from the driver to the phase modulation region. Deactivation of the driver refers to cutting off the power supply of the driver.
- FIG. 11 is a flowchart illustrating a method for determining an activation driver of the optical modulator 100.
- Step S101 the required transmission rate information INF is input to the determination circuit 13 from the outside.
- the requested transmission rate information INF may be output from the optical receiver or the optical transmission / reception system, or may be given as setting information from the user.
- Step S102 The determination circuit 13 determines which one of the drivers 121 to 127 is activated according to the required transmission rate information INF. Then, a signal SIG ⁇ b> 1 designating a driver to be activated is output to the driver control circuit 14 and the switching control circuit 16.
- Step S103 The driver control circuit 14 activates the driver specified by the signal SIG1, and cuts off the power supply to the other drivers.
- Step S104 The switching control circuit 16 switches the connection path between the driver and the phase modulation region by the signal SIG2. As a result, some activated drivers are connected to two or more pairs of phase modulation regions.
- FIG. 12 is a plan view showing the optical modulator 100 when the required transmission rate is high (for example, f1 in FIG. 10).
- “ON” is displayed for the activated driver.
- all of the drivers 121 to 127 are activated and connected to a set of phase modulation regions.
- FIG. 13 is a plan view showing an activation driver and a deactivation driver in the optical modulator 100 when the required transmission rate is low (for example, f2 in FIG. 10).
- the required transmission rate for example, f2 in FIG. 10
- FIG. 13 “ON” is displayed for the activated driver, and “OFF” is displayed for the deactivated driver.
- the drivers 121, 123, 125, and 127 are activated, and the drivers 122, 124, and 126 are deactivated.
- the switching control circuit 16 switches the connection path of the driver output switching circuit 15.
- the driver 121 is connected to the phase modulation regions PM1_1, PM2_1, PM1_2, and PM2_2.
- the driver 123 is connected to the phase modulation areas PM1_3, PM2_3, PM1_4, and PM2_4.
- the driver 125 is connected to the phase modulation regions PM1_5, PM2_5, PM1_6, and PM2_6. That is, the drivers 121, 123, and 125 drive two sets of phase modulation areas.
- FIG. 14 is a plan view schematically showing the configuration of the optical modulator 200 according to the second embodiment.
- the determination circuit 13 has a look-up table (LUT) 131.
- the LUT 131 stores information in which the requested transmission rate information INF is associated with the driver to be activated.
- the LUT 131 is stored in, for example, a storage device provided in the determination circuit 13.
- the LUT 131 may be stored in the determination circuit 13 in advance, may be input from an optical receiver or an optical transmission / reception system, or may be given as setting information from a user.
- FIG. 15 is a flowchart illustrating a method for determining an activation driver of the optical modulator 200.
- Step S201 Step S201 is the same as step S101 in FIG.
- Step S202 The determination circuit 13 compares the requested transmission rate information INF and the LUT 131 to determine which driver to activate among the drivers 121 to 123. Then, a signal SIG1 designating the driver to be activated is output to the driver control circuit 14.
- Steps S203 and S204 are the same as steps S103 and S104 in FIG.
- the optical receiver has an appropriate multilevel value.
- a signal can be transmitted.
- the power supply to the driver which is not used can be cut off, and the power consumed by the driver can be reduced.
- connection switching between the driver and the phase modulation region may be performed as an initial setting at the time of introduction, or at a predetermined timing and frequency as a fine adjustment during operation of the optical transmission / reception system. You may go.
- the driver to be deactivated can be rotated as appropriate. By averaging the frequency of deactivation of a plurality of drivers, it is possible to extend the life of the entire drive circuit.
- the method of reducing power consumption by cutting off the power supply to the inactivation driver described in the above embodiment is not limited to a single Mach-Zehnder optical modulator, but also I (In-phase) / Q ( It can also be applied to a quadrature modulator.
- one activation driver is connected to the phase modulation region connected to one inactivation driver when the transmission rate is low
- one activated driver may be connected to the phase modulation region that has been connected to two or more deactivated drivers as long as the required transmission rate is satisfied. Therefore, it is possible to provide two or more phase modulation regions on one optical waveguide of the light modulation unit, provide two or more drivers, and connect the activated driver to two or more phase modulation regions.
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Abstract
Description
まず、本発明の実施の形態1にかかる光送信器1000について説明する。光送信器1000は、2値(すなわち1ビット)の変調動作を行う光送信器である。図7は、実施の形態1にかかる光送信器1000の構成を模式的に示すブロック図である。光送信器1000は、光源1001及び光変調器100を有する。
f1=1/(2πRC) ・・・(1)
上述の式(1)においては、容量値Cが抵抗値Rよりも支配的な影響を有する。
ステップS101
まず、判定回路13に、外部から要求伝送レート情報INFが入力される。要求伝送レート情報INFは、光受信器や光送受信システムから出力されてもよいし、ユーザから設定情報として与えられてもよい。
判定回路13は、要求伝送レート情報INFに応じて、ドライバ121~127のうち、活性化するものを判定する。そして、活性化するドライバを指定する信号SIG1をドライバ制御回路14及び切替制御回路16に出力する。
ドライバ制御回路14は、信号SIG1で指定されたドライバを活性化し、それ以外のドライバへの電源供給を遮断する。
切替制御回路16は、信号SIG2により、ドライバと位相変調領域との間の接続経路を切り替える。これにより、活性化されたドライバの中には、2対以上の位相変調領域と接続されるものが存在することとなる。
次に、本発明の実施の形態2にかかる光変調器200について説明する。光変調器200は、実施の形態1にかかる光変調器100の具体例である。図14は、実施の形態2にかかる光変調器200の構成を模式的に示す平面図である。光変調器200は、判定回路13が、ルックアップテーブル(LUT:Look Up Table)131を有している。
ステップS201
ステップS201は、図11のステップS101と同様であるので、説明を省略する。
判定回路13は、要求伝送レート情報INFとLUT131とを照合し、ドライバ121~123のうち、活性化するドライバを判定する。そして、活性化するドライバを指定する信号SIG1をドライバ制御回路14に出力する。
ステップS203及びS204は、それぞれ図11のステップS103及びS104と同様であるので、説明を省略する。
なお、本発明は上記実施の形態に限られたものではなく、趣旨を逸脱しない範囲で適宜変更することが可能である。例えば、上述の実施の形態において、ドライバと位相変調領域との間の接続切替は、導入時の初期設定として行ってもよいし、光送受信システムの運用中の微調整として所定のタイミング、頻度で行ってもよい。
12 駆動回路
13、63 判定回路
14 ドライバ制御回路
15 ドライバ制御回路
16 切替制御回路
62 デコード部
100、200 光変調器
111、112、611、612 光導波路
113、114、613、614 光合分波器
121~127、DR61~DR67 ドライバ
131 ルックアップテーブル(LUT)
1000、6000 光送信器
1001、6001 光源
1002、6002 CW光
1003、6003 光信号
DIN 入力デジタル信号
IN 入力光
INF 要求伝送レート情報
OUT 光信号
P1、P2、P5、P6 入力ポート
P3、P4、P7、P8 出力ポート
PM1_1~PM1_7、PM2_1~PM2_7、PM61_1~PM61_7、PM62_1~PM62_4 位相変調領域
S11、S12、S21、S22、S31、S32、S41、S42、S51、S52、S61、S62、S71、S72、B11、B12、B21、B22、B31、B32、B41、B42、B51、B52、B61、B62 スイッチ
Claims (9)
- 光導波路の上に複数の位相変調領域が形成され、入力光を2値変調した光信号を出力する光変調部と、
前記複数の位相変調領域に入力デジタル信号に応じた駆動信号を出力する複数のドライバを有する駆動回路と、
伝送レートを示す情報に基づいて、前記複数のドライバのうち活性化するドライバを判定する判定回路と、
前記判定回路での判定結果で指定されたドライバを活性化し、活性化したドライバ以外のドライバの電源を遮断するドライバ制御回路と、
前記複数のドライバと前記複数の位相変調領域との間の接続を切り替える切替回路と、
前記活性化したドライバから前記複数の位相変調領域に前記駆動信号が印加されるように、前記切替回路を制御する切替制御回路と、を備える、
光変調器。 - 前記判定回路は、
前記伝送レートと、活性化するドライバと、の対応付けが定義されたテーブルを備え、
前記伝送レートを示す情報を前記テーブルと照合して、前記活性化するドライバを判定する、
請求項1に記載の光変調器。 - 前記判定回路は、前記伝送レートを示す情報が示す伝送レートが小さいほど、活性化するドライバの数を少なくする、
請求項1又は2に記載の光変調器。 - 前記光変調部は、2つに分波された前記入力光がそれぞれ2本の前記光導波路を伝搬し、前記2つに分波された前記入力光の両方又は一方を位相変調した後に合波して、前記光信号を生成する、
請求項1乃至3のいずれか一項に記載の光変調器。 - 前記光変調部は、
前記入力光を第1の入力光と第2の入力光に分波する第1の光合分波器と、
前記第1の入力光が伝搬する第1の光導波路と、
前記第2の入力光が伝搬する第2の光導波路と、
前記第1の光導波路から出力される光と前記第2の光導波路から出力される光とを合波して、前記光信号を出力する第2の光合分波器と、
前記第1の光導波路上に形成された複数の第1の位相変調領域と、
前記第2の光導波路上に形成された複数の第2の位相変調領域と、を備える、
請求項4に記載の光変調器。 - 前記光変調部は、
m(mは、2以上の整数)個の前記第1の位相変調領域と、
m個の前記第2の位相変調領域と、を備え、
前記駆動回路は、
m個の前記ドライバを備え、
m個の前記ドライバのうちで活性化されたドライバには、n(nは、2以上の整数)の前記第1の位相変調領域及びn個の前記第2の位相変調領域に、他の活性化されたドライバと重複することなく接続されるものがある、
請求項5に記載の光変調器。 - 光導波路の上に複数の位相変調領域が形成され、入力光を2値変調した光信号を出力する光変調部と、
前記入力光を出力する光源と、
前記複数の位相変調領域に入力デジタル信号に応じた駆動信号を出力する複数のドライバを有する駆動回路と、
伝送レートを示す情報に基づいて、前記複数のドライバのうち活性化するドライバを判定する判定回路と、
前記判定回路での判定結果で指定されたドライバを活性化し、活性化したドライバ以外のドライバの電源を遮断するドライバ制御回路と、
前記複数のドライバと前記複数の位相変調領域との間の接続を切り替える切替回路と、
前記活性化したドライバから前記複数の位相変調領域に前記駆動信号が印加されるように、前記切替回路を制御する切替制御回路と、を備える、
光送信器。 - 光信号を出力する光送信器と、
前記光信号を受信する光受信器と、を備え、
前記光送信器は、
光導波路の上に複数の位相変調領域が形成され、入力光を2値変調した前記光信号を出力する光変調部と、
前記入力光を出力する光源と、
前記複数の位相変調領域に入力デジタル信号に応じた駆動信号を出力する複数のドライバを有する駆動回路と、
伝送レートを示す情報に基づいて、前記複数のドライバのうち活性化するドライバを判定する判定回路と、
前記判定回路での判定結果で指定されたドライバを活性化し、活性化したドライバ以外のドライバの電源を遮断するドライバ制御回路と、
前記複数のドライバと前記複数の位相変調領域との間の接続を切り替える切替回路と、
前記活性化したドライバから前記複数の位相変調領域に前記駆動信号が印加されるように、前記切替回路を制御する切替制御回路と、を備える、
光送受信システム。 - 伝送レートを示す情報に基づいて、光導波路を伝搬する入力光を変調する前記光導波路上に設けられた複数の位相変調領域に入力デジタル信号に応じた駆動信号を出力する複数のドライバのうち、活性化するドライバを判定し、
前記判定により指定されたドライバを活性化し、活性化したドライバ以外のドライバの電源を遮断し、
前記活性化したドライバから前記複数の位相変調領域に前記駆動信号が印加されるように、前記複数のドライバと前記複数の位相変調領域との間の接続を切り替える、
光変調器の制御方法。
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JPH05257102A (ja) * | 1992-03-16 | 1993-10-08 | Nippon Telegr & Teleph Corp <Ntt> | 光位相変調回路 |
JPH05289033A (ja) * | 1992-04-07 | 1993-11-05 | Hitachi Ltd | 直列導波路型光送受信装置 |
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