WO2016092666A1 - 光送信器 - Google Patents
光送信器 Download PDFInfo
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- WO2016092666A1 WO2016092666A1 PCT/JP2014/082825 JP2014082825W WO2016092666A1 WO 2016092666 A1 WO2016092666 A1 WO 2016092666A1 JP 2014082825 W JP2014082825 W JP 2014082825W WO 2016092666 A1 WO2016092666 A1 WO 2016092666A1
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- modulation
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- optical modulator
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- 230000003287 optical effect Effects 0.000 title claims abstract description 605
- 238000001514 detection method Methods 0.000 claims description 28
- 230000005540 biological transmission Effects 0.000 description 46
- 230000007274 generation of a signal involved in cell-cell signaling Effects 0.000 description 24
- 238000000034 method Methods 0.000 description 16
- 238000002834 transmittance Methods 0.000 description 16
- 238000010586 diagram Methods 0.000 description 11
- 238000001228 spectrum Methods 0.000 description 8
- 238000004891 communication Methods 0.000 description 6
- 238000005259 measurement Methods 0.000 description 5
- 230000010363 phase shift Effects 0.000 description 5
- 239000004065 semiconductor Substances 0.000 description 5
- 239000000835 fiber Substances 0.000 description 4
- 239000013307 optical fiber Substances 0.000 description 4
- 230000004075 alteration Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000009977 dual effect Effects 0.000 description 2
- 229910013641 LiNbO 3 Inorganic materials 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000009022 nonlinear effect Effects 0.000 description 1
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- 230000002269 spontaneous effect Effects 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
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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
- G02F1/0123—Circuits for the control or stabilisation of the bias voltage, e.g. automatic bias control [ABC] feedback loops
-
- 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
- G02F1/21—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 by interference
- G02F1/225—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 by interference in an optical waveguide structure
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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
- H04B10/25—Arrangements specific to fibre transmission
-
- 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
-
- 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
- H04B10/54—Intensity modulation
-
- 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
- G02F1/21—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 by interference
- G02F1/212—Mach-Zehnder type
-
- 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
- G02F2201/00—Constructional arrangements not provided for in groups G02F1/00 - G02F7/00
- G02F2201/58—Arrangements comprising a monitoring photodetector
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
Definitions
- the present invention relates to an optical transmitter that transmits an optical signal, and particularly to an optical transmitter including optical modulators connected in multiple stages.
- ASE amplified spontaneous emission
- EDFA erbium-doped fiber amplifier
- WDM wavelength division multiplexing
- each optical modulator corresponds to a modulation format. It is necessary to control the bias voltage of the optical modulator (see, for example, Patent Document 3).
- the first stage is an RZ (Return to Zero) modulator
- the second stage is a DQPSK (Differential Quadrature Phase Shift Keying) modulator.
- RZ Return to Zero
- DQPSK Different Quadrature Phase Shift Keying
- the bias voltage that determines the operating point of the optical modulator is feedback controlled to the point where the optical transmittance of the optical modulator is maximized.
- the modulation signal for example, RZ modulation signal
- the optical transmittance of the optical modulator is maintained to be maximized by feedback control, but the optical signal output from the first-stage optical modulator is modulated. Since there is no loss, the optical input intensity to the second-stage (next-stage) optical modulator (eg, DQPSK modulator) increases, and the feedback control of the bias voltage control circuit in the second-stage optical modulator is unstable. It becomes.
- the bias voltage that determines the operating point of the optical modulator is feedback-controlled to the point where the optical transmittance of the optical modulator is minimized.
- a signal for example, an RZ modulation signal
- the optical transmittance of the optical modulator is maintained to be minimized by feedback control, and therefore, the second-stage optical modulator ( For example, the optical output to the DQPSK modulator is almost zero, and the optical output cannot be obtained.
- an object of the present invention is when switching control of output of a modulation signal input to at least one optical modulator and stop of output of the modulation signal among a plurality of optical modulators connected in series is executed. Even so, an optical transmitter capable of obtaining a stable optical output is provided.
- the optical transmitter of the present invention includes optical modulation units from the first stage to the Nth stage (N is an integer of 2 or more) connected in cascade, and passes through the optical modulation units from the first stage to the Nth stage.
- An optical modulator having an operating point that is changed according to a value of an applied bias voltage, a drive unit that outputs a modulation data signal to the optical modulator, and the output from the optical modulator A light intensity detector that outputs a detection signal corresponding to the intensity of the optical signal, and a bias that controls the bias voltage based on the detection signal and performs feedback control to bring the operating point of the optical modulator closer to the control target point A control unit, and at the time of modulation-on operation of the optical modulator
- the drive unit outputs the modulated data signal to the optical modulator, the optical modulator outputs the optical signal based on the modulated data signal, and the bias control unit sets the control target point in advance.
- the feedback control is executed by setting the control target point to 1, the drive unit stops outputting the modulated data signal, and the bias control unit sets the control target point during the modulation off operation of the optical modulator.
- the feedback control is performed by switching from the first control target point to the second control target point.
- the switching control of the output of the modulation signal input to at least one of the optical modulators connected in series and the stop of the output of the modulation signal is executed.
- FIG. 1 is a block diagram showing an overall configuration of a WDM system including an optical transmitter according to Embodiment 1 of the present invention.
- 2 is a block diagram illustrating a configuration of an optical transmitter according to Embodiment 1.
- FIG. Relationship between bias voltage applied to first optical modulator and output of optical signal output from first optical modulator, and bias voltage applied to first optical modulator and first light intensity It is a figure which shows the relationship with the monitor electric current which a detection part detects, respectively. It is a figure which shows the characteristic of the 1st optical modulator with respect to a bias voltage. It is a block diagram which shows the structure of the optical transmitter which concerns on Embodiment 2 of this invention.
- FIG. 1 is a block diagram showing an overall configuration of a WDM system 10 including an optical transmitter 12 according to Embodiment 1 of the present invention.
- the WDM system 10 includes a plurality of optical transmitters 12 (Tx), an optical multiplexing unit 14, an optical demultiplexing unit 16, and a plurality of optical receivers 18 (Rx).
- the optical multiplexing unit 14 and the optical demultiplexing unit 16 are connected via a transmission path 15.
- Transmission data 11 is input to each of the plurality of optical transmitters 12.
- the transmission data 11 is converted from an electrical signal to an optical signal (electrical / optical conversion) by the optical transmitter 12 to generate transmission light 13 as an optical signal.
- This transmission light 13 is output from the optical transmitter 12.
- Each of the plurality of transmission lights 13 having different wavelengths output from each of the plurality of optical transmitters 12 is wavelength-multiplexed by the optical multiplexing unit 14 and passes through the transmission path 15.
- the received light 17 wavelength-divided by the optical demultiplexing unit 16 is converted from an optical signal to an electrical signal (optical / electrical conversion) in an optical receiver 18, and reception data 19 is output.
- FIG. 2 is a block diagram illustrating a configuration of the optical transmitter 12 according to the first embodiment.
- the optical transmitter 12 includes a light source 100 that outputs continuous light.
- the light source 100 may be disposed outside the optical transmitter 12.
- the light emitted from the light source 100 is incident from the outside to the inside of the optical transmitter 12 and is incident on the first optical modulator 110.
- the light source 100 is, for example, a light emitting element that emits a continuous wave (hereinafter referred to as “CW”), and is, for example, a semiconductor laser.
- CW continuous wave
- the optical transmitter 12 includes a first optical modulation unit 101 in the previous stage (that is, a first optical modulation unit), and a second optical unit in the next stage connected in series (in series) with the first optical modulation unit 101.
- a light modulation unit 102 that is, a second-stage light modulation unit.
- the first light modulation unit 101 modulates input light (for example, continuous light output from the light source 100) according to a first modulation signal 110a (first modulation data signal as an optical modulator drive signal).
- first modulation signal 110a first modulation data signal as an optical modulator drive signal.
- a first drive unit 111a that outputs the first modulation signal 110a and a first detection signal (first detection signal) corresponding to the intensity of the optical signal 110b output from the first optical modulator 110
- the bias voltage is controlled based on the first light intensity detection unit 113 that outputs the light intensity signal 113a and the first light intensity signal 113a, and the operating point of the first light modulator 110 is brought closer to the control target point.
- the first driving unit 111 a includes a first optical modulator driving unit 112 and a first modulation signal generation unit 111.
- the first light modulation unit 101 also controls a first modulation control unit 115 that controls switching of output of the first modulation signal 110a from the first drive unit 111a and stop of output of the first modulation signal 110a.
- a first light intensity information holding unit 116 that records the light intensity information 113b (first light intensity information) transmitted from the first light intensity detecting unit 113.
- the second optical modulation unit 102 converts the input light (for example, the optical signal 110b output from the first optical modulator 110) into the second modulated signal 120a (second modulated data signal as an optical modulator driving signal). )
- a second drive unit 121a that outputs the second modulation signal 120a to the second optical modulator 120, and a detection signal (second detection signal) corresponding to the intensity of the transmission light 13 output from the second optical modulator 120.
- the second light intensity detection unit 123 that outputs the second light intensity signal 123a and the bias voltage is controlled based on the second light intensity signal 123a, and the operating point of the second light modulator 120 Perform feedback control to bring And a second bias control section 124.
- the first light modulator 110 of the first light modulation unit 101 and the second light modulator 120 of the second light modulation unit 102 are arranged in series (in series) via an optical transmission medium (for example, an optical fiber). )It is connected to the.
- an optical transmission medium for example, an optical fiber.
- the first optical modulator 110 and the second optical modulator 120 either a Mach-Zehnder modulator or an electroabsorption modulator, or a combination thereof can be used.
- ⁇ Operation of Optical Transmitter 12 inputting a modulation signal to the optical modulator is referred to as “modulation on (ON) operation”.
- the first modulation signal 110 a is input to the first optical modulator 110.
- the modulation ON operation of the first optical modulator 110 A state in which a modulation signal is input to the optical modulator is referred to as “during modulation ON (ON) operation”.
- Stopping the input of the modulation signal to the optical modulator is called a “modulation off (OFF) operation”.
- the input of the first modulation signal 110 a to the first optical modulator 110 is stopped.
- the modulation OFF operation of the first optical modulator 110 The state in which the input of the modulation signal to the optical modulator is stopped is referred to as “during modulation off (OFF) operation”.
- the input of the first modulation signal 110 a to the first optical modulator 110 is The stopped state is referred to as “during modulation OFF operation of the first optical modulator 110”.
- modulation on / off mainly refers to switching from a state in which the modulation signal is input to the optical modulator to a state in which the input of the modulation signal is stopped.
- modulation ON / OFF of the first optical modulator 110 refers to the input of the first modulated signal 110a from the state in which the first modulated signal 110a is input to the first optical modulator 110. Is switched to a state of stopping.
- the light source 100 outputs continuous light (CW light) toward the first optical modulator 110.
- the CW light output from the light source 100 is input to the first optical modulator 110, modulated based on the first modulated signal 110a input to the first optical modulator 110, and added as an optical signal 110b. Output from the first optical modulator 110.
- the optical signal 110b output from the first optical modulator 110 is transmitted by an optical transmission medium (for example, an optical fiber), input to the second optical modulator 120, and input to the second optical modulator 120.
- the second modulated signal 120a is modulated and output from the second optical modulator 120 and the optical transmitter 12 as transmission light 13 which is an optical signal.
- the CW light output from the light source 100 passes through the first optical modulator 110 and the second optical modulator 120, and is transmitted to the first optical modulator 110 and the second optical modulator 120, respectively. Modulation based on the input first modulated signal 110 a and second modulated signal 120 a is added, and the transmitted light 13 is output from the optical transmitter 12.
- the CW light output from the light source 100 does not necessarily need to be modulated by both the first optical modulator 110 and the second optical modulator 120.
- the CW light output from the light source 100 is modulated in any one of the first optical modulator 110 and the second optical modulator 120 and output from the optical transmitter 12. May be.
- an intensity modulation method or a phase modulation method can be applied to the modulation method in the first optical modulator 110 and the second optical modulator 120.
- the intensity modulation method for example, RZ modulation or NRZ (Non Return to Zero) modulation can be applied.
- the phase modulation system for example, DPSK (Differential Phase Shift Keying), DQPSK (Differential Quadrature Phase Shift Keying), DP-BPSK (Dual Polarization-Binary Phase Shift Keying), or DP-QPSK (Dual Polarization-Quadrature Phase Shift Keying ) Etc. are applicable.
- the first modulation signal generation unit 111 receives transmission data 11 from the outside, generates a first modulation signal 110 a, and outputs the generated first modulation signal 110 a to the first optical modulator driving unit 112. To do.
- the first optical modulator driver 112 amplifies the first modulated signal 110a input from the first modulated signal generator 111, and the amplified first modulated signal 110a is the first optical modulator 110. Output to.
- the first drive unit 111 a includes a first modulation signal generation unit 111 and a first optical modulator drive unit 112. Therefore, the first drive unit 111a generates the first modulated signal 110a based on the transmission data 11 input from the outside, amplifies the first modulated signal 110a, and outputs the first modulated signal 110a to the first optical modulator 110. To do.
- the first light intensity detector 113 includes a semiconductor light receiving element (for example, a photodiode), and monitors and detects the intensity of the optical signal 110b. Specifically, the first light intensity detector 113 converts the light received by the semiconductor light receiving element into a monitor current (first monitor current), and monitors the intensity of the optical signal 110b based on the value of the monitor current. And detect.
- a semiconductor light receiving element for example, a photodiode
- the first light intensity detector 113 generates a first light intensity signal 113a indicating the intensity of the optical signal 110b from the monitor current value, and sends the first light intensity signal 113a to the first bias controller 114. Send. Further, the first light intensity detector 113 detects the intensity of the optical signal 110b when the first optical modulator 110 is in the modulation ON operation, thereby corresponding to the intensity of the optical signal 110b during the modulation ON operation. Light intensity information 113b, which is information, is generated, and the light intensity information 113b is transmitted to the first light intensity information holding unit 116.
- the first light intensity detection unit 113 is not limited to the configuration built in the first light modulator 110, and may be disposed outside the first light modulator 110.
- the first bias control unit 114 controls the operating point of the first optical modulator 110 by applying a bias voltage to the first optical modulator 110. Specifically, using the first light intensity signal 113a transmitted from the first light intensity detector 113, the bias voltage necessary for operating the first optical modulator 110 at an appropriate operating point is set. By performing feedback control, the operating point of the first optical modulator 110 is controlled.
- the first modulation control unit 115 transmits an output command or a stop command to the first modulation signal generation unit 111, and outputs the first modulation signal 110 a from the first modulation signal generation unit 111 and the first modulation signal generation unit 111. Controls the switching of the output stop of the modulation signal 110a. Further, the first modulation control unit 115 links the first bias control unit 114 with a change command (first control signal) in conjunction with transmission of an output command or a stop command to the first modulation signal generation unit 111. To change the control method of the feedback control (control target switching).
- the switching of the output of the first modulation signal 110a and the stop of the output of the first modulation signal 110a is not limited to the configuration in which the first modulation signal generation unit 111 is controlled by the first modulation control unit 115.
- the first drive unit 111a may include a control unit that controls the output of the first modulation signal 110a and the stop of the output of the first modulation signal 110a, for example, the first modulation signal generation unit 111.
- the control unit provided in the first modulation signal generation unit 111 controls the stop of the output of the first modulation signal 110a and the output of the first modulation signal 110a from the first optical modulator driving unit 112. Also good.
- the output of the first modulation signal 110a from the first optical modulator driving unit 112 is controlled by controlling the ON / OFF of the driver output by controlling the power source of the first optical modulator driving unit 112 and the like.
- the stop of the output of the first modulation signal 110a may be controlled.
- the first light intensity information holding unit 116 stores the light intensity information 113b transmitted from the first light intensity detecting unit 113 via the first bias control unit 114.
- the second modulation signal generation unit 121 receives transmission data 11 from the outside, generates a second modulation signal 120 a, and outputs the generated second modulation signal 120 a to the second optical modulator driving unit 122. To do.
- the input light (that is, the optical signal 110b) input to the second optical modulator 120 is modulated based on the second modulated signal 120a input to the second optical modulator 120, and the transmitted light 13 ( (Second optical signal) is output from the second optical modulator 120.
- the second optical modulator driver 122 amplifies the second modulated signal 120 a input from the second modulated signal generator 121, and the amplified second modulated signal 120 a is used as the second optical modulator 120.
- the second drive unit 121 a includes a second modulation signal generation unit 121 and a second optical modulator drive unit 122. Therefore, the second drive unit 121a generates the second modulation signal 120a based on the transmission data 11 input from the outside, amplifies the second modulation signal 120a, and outputs the second modulation signal 120a to the second optical modulator 120. To do.
- the second light intensity detection unit 123 includes a semiconductor light receiving element (for example, a photodiode), and monitors and detects the intensity of the transmission light 13. Specifically, the second light intensity detector 123 converts the light received by the semiconductor light receiving element into a monitor current (second monitor current), and monitors the intensity of the transmission light 13 based on the value of the monitor current. And detect. The second light intensity detection unit 123 generates a second light intensity signal 123a indicating the intensity of the transmission light 13 from the monitor current value, and the second light intensity signal 123a is used as the second bias control unit. 124.
- the second light intensity detection unit 123 is not limited to the configuration built in the second light modulator 120, and may be disposed outside the second light modulator 120.
- the second bias controller 124 applies a bias voltage to the second optical modulator 120 to control the operating point of the second optical modulator 120. Specifically, using the second light intensity signal 123a transmitted from the second light intensity detector 123, the bias voltage necessary for operating the second optical modulator 120 at an appropriate operating point is set. The operating point of the second optical modulator 120 is controlled by performing feedback control.
- FIG. 3 shows the relationship between the bias voltage applied to the first optical modulator 110 and the output of the optical signal 110b, and the bias voltage applied to the first optical modulator 110 and the first light intensity detector 113. It is a figure which shows the relationship with the monitor electric current which each detects.
- the vertical axis indicates the output value (optical output intensity) of the optical signal 110b of the first optical modulator 110 and the output value of the monitor current detected by the first optical intensity detector 113.
- the horizontal axis represents the value of the bias voltage applied to the first optical modulator 110. That is, a curve a1 shown in FIG. 3 indicates an optical output value (optical output intensity) with respect to a bias voltage applied to the first optical modulator 110, and a curve m1 is applied to the first optical modulator 110.
- the output value of the monitor current detected by the first light intensity detector 113 with respect to the bias voltage is shown.
- the Mach-Zehnder modulator has a characteristic that the light transmittance and the monitor current change based on the value of the applied bias voltage. Therefore, by controlling the bias voltage using the monitor current value as an index, the light transmittance and the light output intensity of the light modulator can be controlled.
- the example shown in FIG. 3 indicates that the output of the first optical modulator 110 when the bias voltage is V1 is P1, and the monitor current value when the output is P1 is M1. Is shown. Therefore, for example, by performing feedback control of the bias voltage so that the monitor current value becomes M1, the output of the first optical modulator 110 is controlled to become P1.
- FIG. 4 is a diagram showing the characteristics of the first optical modulator 110 with respect to the bias voltage.
- the vertical axis represents the theoretical light output value (light transmittance) obtained from the optical modulator characteristic curve, and the horizontal axis is applied to the first optical modulator 110. Indicates the value of the bias voltage.
- the first optical modulator 110 is configured so that the light transmittance of the first optical modulator 110 is maximized when the first optical modulator 110 is in the modulation ON operation.
- the operating point of the optical modulator 110 is set. That is, as shown in FIG. 4, the first bias control unit 114 receives the first light intensity transmitted from the first light intensity detection unit 113 when the first optical modulator 110 performs the modulation ON operation.
- a control target for feedback control is set such that the position of the operating point of the first optical modulator 110 is set to a position where the light transmittance of the first optical modulator 110 is maximized. Point) is set, and feedback control is executed so that the operating point approaches the set control target point (first control target point).
- the optical signal 110b actually output from the first optical modulator 110 has a modulation loss.
- the actual output from may be different from the theoretical output for the bias voltage (ie, the output determined from the optical modulator characteristic curve).
- the bias voltage applied to the first optical modulator 110 is V1
- the output (intensity) of the optical signal 110b actually output from the first optical modulator 110 is obtained from the optical modulator characteristic curve. It becomes lower than the required Pmax, for example, P1.
- the bias voltage applied to the first optical modulator 110 is the same.
- the intensity of the optical signal (for example, the optical signal 110b) input to the next optical modulator (for example, the second optical modulator 120) is May be too high. That is, when the output of the first modulation signal 110a is switched from ON to OFF, the control target of feedback control is not changed (for example, the bias voltage is maintained at V1 by controlling the light transmittance to be maximum).
- the intensity of the optical signal 110b output from the first optical modulator 110 may be too high when the first optical modulator 110 is turned off.
- the first bias control unit 114 determines that the position of the operating point of the first optical modulator 110 is the light of the first optical modulator 110.
- a control target for feedback control is set so that the transmittance is set to the maximum position (that is, the control target point is set to a predetermined first control target point), and feedback control is executed. Therefore, when the control target of the feedback control is not changed, the bias voltage is maintained at V1, for example.
- the bias voltage is maintained at, for example, V1 during the modulation OFF operation of the first optical modulator 110, the modulation loss of the optical signal 110b disappears during the modulation OFF operation, so that the intensity of the optical signal 110b is, for example, Pmax ( Pmax> P1).
- the intensity of the optical signal (for example, optical signal 110b) input from the preceding optical modulator (for example, first optical modulator 110) to the next optical modulator (for example, second optical modulator 120) is If it becomes too high, the feedback control of the bias voltage in the optical modulator at the next stage may become unstable. Therefore, it is desirable that the intensity of the optical signal input from the preceding optical modulator to the succeeding optical modulator is the same before and after switching between the modulation ON operation and the modulation OFF operation in the preceding optical modulator.
- the feedback control of the bias voltage applied to the first optical modulator 110 during the modulation OFF operation is executed based on the intensity of the optical signal 110b during the modulation ON operation of the first optical modulator 110.
- the first light intensity information holding unit 116 records the light intensity information 113b transmitted from the first light intensity detecting unit 113 when the first optical modulator 110 performs the modulation ON operation.
- the light intensity information 113b corresponds to the intensity (for example, the output value P1 shown in FIG. 3) of the optical signal 110b output from the first optical modulator 110 when the first optical modulator 110 performs the modulation ON operation.
- the light intensity information 113b is, for example, a monitor current value (for example, the output value M1 shown in FIG. 3) acquired by the first light intensity detector 113 when the first optical modulator 110 is in a modulation ON operation.
- the monitor current value acquired by the first light intensity detection unit 113 is, for example, a monitor current value corresponding to the average output value of the optical signal 110b during the modulation ON operation of the first optical modulator 110. is there.
- an average output value of the monitor current when the first optical modulator 110 is in the modulation ON operation may be used as the light intensity information 113b.
- the monitor current value corresponding to the maximum output value of the optical signal 110b during the modulation ON operation of the first optical modulator 110 may be used as the light intensity information 113b.
- the first modulation control unit 115 transmits a stop command for the first modulation signal 110a to the first modulation signal generation unit 111 to generate the first modulation signal.
- the output of the first modulated signal 110a by the unit 111 is stopped, the input of the first modulated signal 110a to the first optical modulator 110 is stopped.
- the first modulation control unit 115 transmits a stop instruction for the first modulation signal 110a to the first modulation signal generation unit 111, and the first When the input of the first modulation signal 110a to the optical modulator 110 is stopped, the first modulation control unit 115 controls the feedback control by the first bias control unit 114 to the first bias control unit 114. Send a method change command.
- the first bias control unit 114 When the first bias control unit 114 receives an instruction to change the control method of the feedback control, the first bias control unit 114 switches the control target point using the light intensity information 113b recorded in the first light intensity information holding unit 116, and The bias voltage applied to the first optical modulator 110 so that the intensity of the optical signal 110b output from the first optical modulator 110 is the same before and after the modulation ON / OFF of the optical modulator 110. Execute feedback control.
- the first bias control unit 114 determines that the intensity of the optical signal 110b output when the first optical modulator 110 is in the modulation OFF operation is higher than that when the first optical modulator 110 is in the modulation ON operation.
- the control target of feedback control is switched (the control target point is set to the first control target) so that the intensity is the same as the intensity of the optical signal 110b indicated by the light intensity information 113b recorded in the one light intensity information holding unit 116.
- the feedback control is executed by switching from the point to the second control target point). That is, during the modulation OFF operation of the first optical modulator 110, the first bias control unit 114 performs light intensity information 113b corresponding to the monitor current value detected by the first light intensity detection unit 113 during the modulation OFF operation.
- the feedback control is executed so as to be the same as 113b).
- the light intensity information 113b held in the first light intensity information holding unit 116 is feedback controlled when the input of the first modulation signal 110a to the first optical modulator 110 is switched from ON to OFF.
- a second control target point when the control target is switched is shown. Accordingly, during the modulation off operation of the first optical modulator 110, the first drive unit 111a stops outputting the first modulation signal 110a, and the first bias control unit 114 sets the control target point to the first control.
- the feedback control is executed by switching from the target point to the second control target point.
- the bias voltage is controlled so that the actual intensity (output value) of the optical signal 110b during the modulation OFF operation of the first optical modulator 110 is P1, and at this time, the first optical modulator 110
- the applied bias voltage is, for example, V2.
- the intensity of the optical signal 110b output when the first optical modulator 110 is in the modulation OFF operation is recorded in the first optical intensity information holding unit 116 when the first optical modulator 110 is in the modulation ON operation. It is not necessary that the intensity of the optical signal 110b indicated by the optical intensity information 113b is exactly the same as the intensity of the optical signal 110b output when the first optical modulator 110 is turned off. It may be the same intensity as the intensity of the optical signal 110b indicated by the light intensity information 113b recorded in the first light intensity information holding unit 116 at the time of the modulation ON operation of one optical modulator 110.
- the intensity of the optical signal 110b output when the first optical modulator 110 is modulated OFF is the same as that when the first optical modulator 110 is modulated ON.
- the feedback control method is switched during the modulation OFF operation of the first optical modulator 110 so that the intensity is the same as the intensity of the optical signal 110b indicated by the optical intensity information 113b recorded in the optical intensity information holding unit 116 of the first optical intensity information.
- fluctuations in the intensity of the optical signal 110b can be suppressed before and after the modulation ON / OFF, so that the second optical signal 110b output when the first optical modulator 110 performs the modulation OFF operation is input.
- the feedback control of the bias voltage in the optical modulator 120 can be stabilized.
- the intensity of the optical signal 110b output from the first optical modulator 110 can be kept constant during the operation of the optical transmitter 12, the first modulated signal 110a in the first optical modulator 110 is maintained. And the stop of the output of the first modulation signal 110a can be dynamically switched, and the second light of the next stage is irrespective of the state of the modulation ON operation or the modulation OFF operation in the first optical modulator 110.
- the intensity of the optical signal 110b input to the modulator 120 can be made constant.
- the control target of the feedback control is set such that the operating point is set at a position where the light transmittance of the first optical modulator 110 is maximized when the modulation of the first optical modulator 110 is performed.
- the example in which the first control target point) is set has been described.
- the light transmittance of the first optical modulator 110 during the modulation ON operation of the first optical modulator 110 is not necessarily the maximum.
- the control target (first control target point) of the feedback control is set so that the operating point is set at a position where the light transmittance of the first optical modulator 110 becomes 50% during the modulation ON operation. Good.
- the first modulation signal input to the first optical modulator 110 is set by setting the light transmittance (for example, 50%) at which an optical output greater than at least zero is obtained in the first optical modulator 110 in the previous stage. Even when the switching control for stopping the output of 110a and the output of the first modulated signal 110a is executed, the optical waveform (optical signal) modulated by the second optical modulator 120 at the next stage is used. It can be output from the optical transmitter 12.
- the light transmittance for example, 50%
- the example in which the bias voltage is switched from the voltage V1 to the voltage V2 during the modulation OFF operation of the first optical modulator 110 is shown.
- the first optical modulator before and after the modulation ON / OFF may be switched so that the fluctuation of the intensity of the optical signal 110b output from 110 is suppressed, and the bias voltage value before and after the modulation ON / OFF is not limited.
- the operation of the first optical modulation unit 101 when a Mach-Zehnder modulator is used as the first optical modulator 110 has been specifically described.
- the present invention provides a Mach-Zehnder modulator as the optical modulator.
- the present invention can also be applied when other optical modulators are used.
- the relationship between the bias voltage to be applied and the light transmittance may vary depending on the type of optical modulator used, as described in the first embodiment, the output is performed when the first optical modulator 110 performs the modulation OFF operation.
- the intensity of the optical signal 110b to be transmitted is the same as the intensity of the optical signal 110b indicated by the optical intensity information 113b recorded in the first optical intensity information holding unit 116 when the first optical modulator 110 is in the modulation ON operation.
- the same effect as that of the optical transmitter 12 described above can be obtained.
- FIG. FIG. 5 is a block diagram showing a configuration of the optical transmitter 22 according to Embodiment 2 of the present invention.
- the optical transmitter 22 according to the second embodiment corresponds to the optical transmitter 12 in the WDM system 10 described in the first embodiment.
- the optical transmitter 22 according to the second embodiment is based on the first embodiment in that the second optical modulation unit 202 further includes a second modulation control unit 125 and a second light intensity information holding unit 126. Different from the optical transmitter 12. Except for this point, the optical transmitter 22 according to the second embodiment is the same as the optical transmitter 12 according to the first embodiment. Therefore, in the optical transmitter 22 shown in FIG. 5, the same or corresponding components as those of the optical transmitter 12 shown in FIG.
- the second light intensity detection unit 123 in the second light modulation unit 202 detects the intensity of the transmission light 13 (second optical signal) at the time of the modulation ON operation of the second light modulator 120.
- Second light intensity information 123b which is information corresponding to the intensity of the transmission light 13 at the time of the modulation ON operation of the second optical modulator 120, is generated, and the second light intensity information 123b is generated as the second light intensity information.
- the data is transmitted to the holding unit 126.
- the second modulation control unit 125 in the second light modulation unit 202 corresponds to the first modulation control unit 115 in the first light modulation unit 101 and has the same function as the first modulation control unit 115. That is, the second modulation control unit 125 transmits an output command or a stop command to the second modulation signal generation unit 121, and outputs the second modulation signal 120 a from the second modulation signal generation unit 121 and the second modulation signal generation unit 121. The switching of the stop of the output of the second modulation signal 120a is controlled. Further, the second modulation control unit 125 interlocks with the transmission of the output command or the stop command to the second modulation signal generation unit 121, and the second bias control unit 124 receives a change command (second control signal). To change the control method of the feedback control (control target switching).
- the switching of the output of the second modulation signal 120a and the stop of the output of the second modulation signal 120a is not limited to the configuration in which the second modulation signal generation unit 121 is controlled by the second modulation control unit 125.
- a control unit that controls the output of the second modulation signal 120a and the stop of the output of the second modulation signal 120a may be provided inside the second drive unit 121a.
- the second modulation signal generation unit 121 may be provided.
- the control unit provided in the second modulation signal generation unit 121 controls the stop of the output of the second modulation signal 120a and the output of the second modulation signal 120a from the second optical modulator driving unit 122. Also good.
- the output of the second modulation signal 120a from the second optical modulator driving unit 122 is controlled by controlling the ON / OFF of the driver output by controlling the power source of the second optical modulator driving unit 122 and the like.
- the stop of the output of the second modulation signal 120a may be controlled.
- the second light intensity information holding unit 126 in the second light modulation unit 202 corresponds to the first light intensity information holding unit 116 in the first light modulation unit 101, and the first light intensity information holding unit 116 and Has the same function. That is, the second light intensity information holding unit 126 stores the second light intensity information 123b transmitted from the second light intensity detection unit 123 via the second bias control unit 124.
- the second light intensity information 123b in the second light modulation unit 202 corresponds to the first light intensity information 113b in the first light modulation unit 101. That is, the second light intensity information 123b is information corresponding to the intensity of the transmission light 13 output from the second optical modulator 120 when the second optical modulator 120 is in the modulation ON operation.
- each of the first optical modulation unit 101 and the second optical modulation unit 202 of the optical transmitter 22 is the same as the components of the first optical modulation unit 101 described in the first embodiment.
- each of the first optical modulation unit 101 and the second optical modulation unit 202 in the optical transmitter 22 is the same as the first optical modulation unit 101 described in the first embodiment because it has corresponding components. Operates and has similar functions. That is, when the second bias control unit 124 receives the feedback control control method change command from the second modulation control unit 125, the second light intensity information recorded in the second light intensity information holding unit 126.
- the control target point is switched using 123b so that the intensity of the second optical signal output from the second optical modulator 120 is the same before and after the modulation ON / OFF of the second optical modulator 120.
- feedback control of the bias voltage applied to the second optical modulator 120 is executed.
- the second bias control unit 124 determines that the intensity of the transmission light 13 that is output when the second optical modulator 120 is in the modulation OFF operation is the second bias control unit 124 that is in the first state when the second optical modulator 120 is in the modulation ON operation.
- the control target of the feedback control is switched (the control target point is set to the first target point) so that the intensity is the same as the intensity of the transmission light 13 indicated by the second light intensity information 123b recorded in the second light intensity information holding unit 126.
- the control target point is switched from the control target point to the second control target point) and feedback control is executed.
- the second bias control unit 124 performs the second light corresponding to the monitor current value detected by the second light intensity detection unit 123 during the modulation OFF operation.
- the intensity information 123b is the second intensity information 123b held in the second intensity information holding section 126 (that is, the second intensity information holding section 126 during the modulation ON operation of the second optical modulator 120).
- the feedback control is executed so as to be the same as the second light intensity information 123b) recorded in the above.
- the second light intensity information 123b held in the second light intensity information holding unit 126 is used when the input of the second modulation signal 120a to the second optical modulator 120 is switched from ON to OFF. Shows the second control target point when the control target of the feedback control is switched. Accordingly, during the modulation off operation of the second optical modulator 120, the second drive unit 121a stops outputting the second modulation signal 120a, and the second bias control unit 124 sets the control target point to the first control. The feedback control is executed by switching from the target point to the second control target point. Therefore, the intensity of the transmission light 13 output from the second optical modulator 120 can be kept constant during the operation of the optical transmitter 22.
- the first modulation control unit 115 and the second modulation control unit 125 of the optical transmitter 22 operate independently of each other. Further, the first bias control unit 114 and the second bias control unit 124 switch the bias voltage control method independently of each other. That is, for example, during the modulation off operation of the first optical modulator 110, the first bias control unit 114 sets the control target point from the first control target point independently of the second optical modulation unit 202. The feedback control is executed by switching to the second control target point. Similarly, for example, during the modulation off operation of the second optical modulator 120, the second bias control unit 124 sets the control target point to the first control target point independently of the first optical modulation unit 101. The feedback control is executed by switching to the second control target point. Note that the control target points set in each of the first light modulation unit 101 and the second light modulation unit 202 may be different from each other.
- the modulation ON / OFF can be switched independently of each other. Therefore, when the optical transmitter 22 is operated, the first optical modulation unit
- the combination of modulation schemes by the unit 101 and the second light modulation unit 202 can be dynamically changed.
- the optical transmitter 22 in which a plurality of optical modulators (the first optical modulator 110 and the second optical modulator 120) are connected in cascade. Before and after stopping the first modulation signal 110a that drives the first optical modulator 110 in the previous stage, the fluctuation of the intensity of the optical signal 110b input to the second optical modulator 120 in the next stage is suppressed. Therefore, stable feedback control can be realized in the second optical modulator 120.
- the optical transmitter 22 can keep the intensity of the optical signal 110b constant before and after the modulation ON / OFF of the first optical modulator 110, and further the modulation ON operation of the first optical modulator 110.
- the intensity of the transmission light 13 can be kept constant before and after the modulation ON / OFF of the second optical modulator 120 regardless of the state of the modulation OFF operation. Therefore, the same optical output can be obtained from the optical transmitter 22 before and after the modulation ON / OFF in each optical modulator regardless of the state of the modulation ON operation or the modulation OFF operation in each optical modulator of the optical transmitter 22. .
- the combination of modulation schemes by the first optical modulation unit 101 and the second optical modulation unit 202 can be dynamically changed.
- An optical modulation signal (transmission light 13) in which the modulation signals are combined can be obtained.
- FIG. 6 is a diagram illustrating a spectrum of an optical signal passing through the transmission line 15 when the second optical modulator 120 is in a modulation ON operation.
- OSNR optical Signal to Noise Ratio
- the resolution is generally set to 0.1 nm.
- the spectrum of the optical signal is broadened by the modulation of the CW light, the measurement target spectrum may not be within the range of 0.1 nm.
- the intensity of the optical signal can be measured if the measurement resolution is expanded to a range where the spectrum of the modulated optical signal can be accommodated. Therefore, it cannot measure with high accuracy.
- FIG. 7 is a diagram illustrating a spectrum of an optical signal passing through the transmission line 15 when each of the first optical modulator 110 and the second optical modulator 120 is switched from the modulation ON operation to the modulation OFF operation.
- the optical transmitter 22 according to the second embodiment includes all the optical modulators of the optical transmitter 22 (that is, the first optical modulator 110 and the optical transmitter 22 when the optical transmitter 22 operates. Even when the second optical modulator 120) is dynamically switched to the modulation OFF operation, unmodulated CW light maintaining the same light output intensity as that during the modulation ON operation of the second optical modulator 120 is obtained. Therefore, OSNR measurement can be performed with a measurement resolution of 0.1 nm, and OSNR measurement can be performed with high accuracy even in a WDM communication environment.
- FIG. FIG. 8 is a block diagram showing a configuration of the optical transmitter 32 according to Embodiment 3 of the present invention.
- the optical transmitter 32 according to the third embodiment corresponds to the optical transmitter 12 in the WDM system 10 described in the first embodiment.
- an optical modulation unit for example, the nth optical modulation unit 303
- the optical transmitter 32 according to the third embodiment is the same as the optical transmitter 22 according to the second embodiment. Therefore, in the optical transmitter 32 shown in FIG. 8, the same or corresponding components as those of the optical transmitter 22 shown in FIG.
- the optical transmitter 32 includes n stages (n is 3). ⁇ n ⁇ N, where N is an integer of 4 or more)
- An example of an optical transmitter connected in series that is, an optical transmitter having an n-stage optical modulation unit
- the nth optical modulation unit 303 shown in FIG. 8 is an optical modulation unit that is cascade-connected to the nth stage counted from the first optical modulation unit 101 that is the first stage among the plurality of optical modulation units. And is connected in cascade with the (n ⁇ 1) -th stage light modulation section.
- the nth optical modulation unit 303 described in the third embodiment is at least one of the optical modulation units from the first stage to the Nth stage.
- the n-th light modulation unit 303 has another light modulation unit (for example, the (n ⁇ 1) -th light modulation unit, the (n ⁇ 2) -th step) when the light modulation unit has an n-stage configuration.
- the present invention is also applied to a light modulation unit or the like.
- the nth optical modulation unit 303 described in the third embodiment includes, for example, the same or corresponding components as the second optical modulation unit 202 among the plurality of optical modulation units included in the optical transmitter 32. .
- the nth optical modulator 130 corresponds to the second optical modulator 120.
- Other components have the same correspondence. That is, the nth modulation signal generation unit 131 corresponds to the second modulation signal generation unit 121.
- the nth driving unit 131a corresponds to the second driving unit 121a.
- the nth optical modulator driver 132 corresponds to the second optical modulator driver 122.
- the nth light intensity detection unit 133 corresponds to the second light intensity detection unit 123.
- the nth bias control unit 134 corresponds to the second bias control unit 124.
- the nth modulation control unit 135 corresponds to the second modulation control unit 125.
- the nth light intensity information holding unit 136 corresponds to the second light intensity information holding unit 126.
- the n-th modulation signal 130a (the n-th modulation data signal as the optical modulator driving signal) corresponds to the second modulation signal 120a.
- the nth light intensity signal 133a as the detection signal (nth detection signal) corresponds to the second light intensity signal 123a.
- the nth light intensity information 133b corresponds to the second light intensity information 123b.
- the nth optical modulation unit 303 of the optical transmitter 32 has the same or corresponding components as those of the second optical modulation unit 202 described in the second embodiment, the second optical modulation unit 303 described in the second embodiment.
- the operation is the same as that of the second light modulation unit 202 and has the same function. That is, when the n-th bias control unit 134 receives a change command of the control method of feedback control from the n-th modulation control unit 135, the n-th light intensity information recorded in the n-th light intensity information holding unit 136.
- the control target point is switched using 133b so that the intensity of the nth optical signal output from the nth optical modulator 130 is the same before and after the modulation ON / OFF of the nth optical modulator 130.
- feedback control of the bias voltage applied to the nth optical modulator 130 is executed.
- the nth bias control unit 134 controls the nth optical signal (for example, the transmission light 13) output from the nth optical modulator 130 when the nth optical modulator 130 performs the modulation OFF operation.
- the intensity is the same as the intensity of the nth optical signal indicated by the nth optical intensity information 133b recorded in the nth optical intensity information holding unit 136 when the nth optical modulator 130 is in the modulation ON operation.
- the control target of feedback control is switched (the control target point is switched from the first control target point to the second control target point and set), and the feedback control is executed.
- the nth bias control unit 134 performs the nth light corresponding to the monitor current value detected by the nth light intensity detection unit 133 during the modulation OFF operation.
- the intensity information 133b is the n-th light intensity information 133b held in the n-th light intensity information holding unit 136 (that is, the n-th light intensity information holding unit 136 during the modulation ON operation of the n-th light modulator 130).
- the feedback control is executed so as to be the same as the n-th light intensity information 133b) recorded in the above.
- the nth light intensity information 133b held in the nth light intensity information holding unit 136 is used when the input of the nth modulation signal 130a to the nth optical modulator 130 is switched from ON to OFF. Shows the second control target point when the control target of the feedback control is switched. Therefore, at the time of the modulation off operation of the nth optical modulator 130, the nth drive unit 131a stops outputting the nth modulation signal 130a, and the nth bias control unit 134 sets the control target point to the first control. The feedback control is executed by switching from the target point to the second control target point. Therefore, the intensity of the nth optical signal output from the nth optical modulator 130 can be kept constant during the operation of the optical transmitter 32.
- each of the modulation control units operates independently of each other.
- Each of the control units switches the control method of the bias voltage independently of each other.
- the nth bias control unit 134 sets the control target point from the first control target point to the second independent of the other optical modulation units.
- the control target point is switched to execute feedback control. Note that the control target points set in each of the optical modulation units in the optical transmitter 32 may be different from each other.
- modulation can be switched on / off independently in any of the optical modulation units from the first optical modulation unit 101 to the nth optical modulation unit 303, so that the optical transmitter In the operation of 32, the combination of modulation schemes by arbitrary light modulation units from the first light modulation unit 101 to the nth light modulation unit 303 can be dynamically changed.
- the optical modulator of the previous stage for example, the (n ⁇ 1) th stage ( n-1) before and after stopping the modulation signal for driving the optical modulator
- the intensity of the optical signal input to the optical modulator at the next stage for example, the nth optical modulator 130 at the nth stage. Since the fluctuation is suppressed, stable feedback control can be realized in the optical modulator at the next stage.
- the optical transmitter 32 includes optical modulators before and after modulation ON / OFF in an arbitrary optical modulation unit among the optical modulation units from the first optical modulation unit 101 to the nth optical modulation unit 303.
- the intensity of the optical signal output from can be kept constant. Therefore, the same optical output can be obtained from the optical transmitter 32 before and after the modulation ON / OFF in each optical modulator regardless of the state of the modulation ON operation or the modulation OFF operation in each optical modulator of the optical transmitter 32. .
- the combination of modulation schemes by a plurality of optical modulation units can be dynamically changed, so that an optical modulation signal (arbitrary modulated signal) combined from the optical transmitter 32 ( Transmitted light 13) can be obtained.
- the optical transmitter 32 As described above, according to the optical transmitter 32 according to the third embodiment, among the plurality of optical modulators connected in multiple stages, the output of the modulation signal input to an arbitrary optical modulator and the output of the modulation signal are stopped.
- an optical transmitter capable of outputting an optical waveform (optical signal) subjected to arbitrary modulation by performing stable feedback control in each optical modulator even when switching control is performed can do.
- each optical transmitter for example, the optical transmitter 12
- Optical transmitters 12, 22, and 32 that can perform stable feedback control and output optical waveforms (optical signals) subjected to arbitrary modulation can be provided.
- 10 WDM system 11 transmission data, 12, 22, 32 optical transmitter, 13 transmission light, 14 optical multiplexing unit, 15 transmission path, 16 optical demultiplexing unit, 17 received light, 18 optical receiver, 19 received data, 100 Light source, 101 first light modulator (first stage light modulator), 102, 202 second light modulator (second stage light modulator), 110 first light modulator, 110a first Modulation signal, 110b optical signal, 111 first modulation signal generator, 112 first optical modulator driver, 113 first light intensity detector, 113a first light intensity signal, 113b first light intensity information , 114, first bias control unit, 115, first modulation control unit, 116, first light intensity information holding unit, 120, second optical modulator, 12 a second modulated signal, 121 second modulated signal generator, 122 second optical modulator driver, 123 second light intensity detector, 123a second light intensity signal, 123b second light intensity information , 124 second bias control unit, 125 second modulation control unit, 126 second light intensity information holding unit, 130 n th optical modulator,
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Abstract
Description
<WDMシステム10の構成及び動作>
図1は、本発明の実施の形態1に係る光送信器12を含むWDMシステム10の全体構成を示すブロック図である。
図2は、実施の形態1に係る光送信器12の構成を示すブロック図である。
次に、光送信器12の動作について説明する。なお、本明細書において、光変調器に変調信号が入力されることを「変調オン(ON)動作」といい、例えば、第1の光変調器110に第1の変調信号110aが入力されることを「第1の光変調器110の変調ON動作」という。また、光変調器に変調信号が入力されている状態を「変調オン(ON)動作時」といい、例えば、第1の光変調器110に第1の変調信号110aが入力されている状態を「第1の光変調器110の変調ON動作時」という。また、光変調器への変調信号の入力が停止することを「変調オフ(OFF)動作」といい、例えば、第1の光変調器110への第1の変調信号110aの入力が停止することを「第1の光変調器110の変調OFF動作」という。また、光変調器への変調信号の入力が停止している状態を「変調オフ(OFF)動作時」といい、例えば、第1の光変調器110への第1の変調信号110aの入力が停止されている状態を「第1の光変調器110の変調OFF動作時」という。
第2の変調信号生成部121は、外部から送信データ11が入力され、第2の変調信号120aを生成し、生成された第2の変調信号120aを第2の光変調器駆動部122に出力する。第2の光変調器120に入力した入力光(すなわち、光信号110b)は、第2の光変調器120に入力される第2の変調信号120aに基づく変調が加えられて、送信光13(第2の光信号)として第2の光変調器120から出力される。
次に、第1の光変調器110としてマッハツェンダ変調器を用いた場合の第1の光変調部101の動作について具体的に説明する。
図3は、第1の光変調器110に印加されるバイアス電圧と光信号110bの出力との関係、及び第1の光変調器110に印加されるバイアス電圧と第1の光強度検出部113が検出するモニタ電流との関係をそれぞれ示す図である。図3に示されるグラフにおいて、縦軸は、第1の光変調器110の光信号110bの出力値(光出力強度)及び第1の光強度検出部113が検出するモニタ電流の出力値を示し、横軸は、第1の光変調器110に印加されるバイアス電圧の値を示す。すなわち、図3において示される曲線a1は、第1の光変調器110に印加されるバイアス電圧に対する光出力値(光出力強度)を示し、曲線m1は、第1の光変調器110に印加されるバイアス電圧に対する第1の光強度検出部113が検出するモニタ電流の出力値を示す。
図5は、本発明の実施の形態2に係る光送信器22の構成を示すブロック図である。
実施の形態2に係る光送信器22は、実施の形態1で説明したWDMシステム10における光送信器12に対応する。実施の形態2に係る光送信器22は、第2の光変調部202に第2の変調制御部125と第2の光強度情報保持部126とをさらに備える点が、実施の形態1に係る光送信器12と異なる。この点を除いて、実施の形態2に係る光送信器22は、実施の形態1に係る光送信器12と同じである。したがって、図5に示される光送信器22において、図2に示される光送信器12の構成要素と同一又は対応する構成要素については、図2に示される符号と同じ符号を付す。
図7に示されるように、実施の形態2に係る光送信器22は、光送信器22の動作時において、光送信器22の全ての光変調器(すなわち、第1の光変調器110及び第2の光変調器120)を動的に変調OFF動作に切り替えた場合であっても、第2の光変調器120の変調ON動作時と同じ光出力強度を維持した無変調CW光を得ることができるので、測定分解能0.1nmでのOSNR測定が可能となり、WDM通信環境下においても精度良くOSNR測定が実施可能となる。
図8は、本発明の実施の形態3に係る光送信器32の構成を示すブロック図である。
実施の形態3に係る光送信器32は、実施の形態1で説明したWDMシステム10における光送信器12に対応する。実施の形態3に係る光送信器32は、第1の光変調部101及び第2の光変調部202に加えて、さらに、光変調部(例えば、第nの光変調部303)が縦列に接続され、光変調部が3段以上備えられている点で、実施の形態2に係る光送信器22と異なる。この点を除いて、実施の形態3に係る光送信器32は、実施の形態2に係る光送信器22と同じである。したがって、図8に示される光送信器32において、図5に示される光送信器22の構成要素と同一又は対応する構成要素については、図5に示される符号と同じ符号を付す。
Claims (10)
- 縦列接続された1段目からN段目(Nは2以上の整数)までの光変調部を備え、1段目からN段目までの前記光変調部を通過した光信号である送信光を出力する光送信器であって、
1段目からN段目までの前記光変調部の内の少なくとも一つの光変調部が、
入力光を変調して光信号を出力すると共に、印加されるバイアス電圧の値に応じて変更される動作点を持つ光変調器と、
前記光変調器に変調データ信号を出力する駆動部と、
前記光変調器から出力される前記光信号の強度に応じた検出信号を出力する光強度検出部と、
前記検出信号に基づいて前記バイアス電圧を制御して、前記光変調器の動作点を制御目標点に近づけるフィードバック制御を行うバイアス制御部と、
を有し、
前記光変調器の変調オン動作時には、前記駆動部は前記変調データ信号を前記光変調器に出力し、前記光変調器は前記変調データ信号に基づく前記光信号を出力し、前記バイアス制御部は前記制御目標点を予め決められた第1の制御目標点に設定して前記フィードバック制御を実行し、
前記光変調器の変調オフ動作時には、前記駆動部は前記変調データ信号の出力を停止し、前記バイアス制御部は前記制御目標点を前記第1の制御目標点から第2の制御目標点に切り替えて前記フィードバック制御を実行する
ことを特徴とする光送信器。 - 前記変調オフ動作時には、前記バイアス制御部は、前記変調オフ動作時における前記光信号の強度が、前記変調オン動作時における前記光信号の強度と同じになるように、前記制御目標点を前記第1の制御目標点から前記第2の制御目標点に切り替えることを特徴とする請求項1に記載の光送信器。
- 前記駆動部から出力される前記変調データ信号の出力及び前記変調データ信号の出力の停止の切り替えを制御する変調制御部をさらに備えることを特徴とする請求項1又は2に記載の光送信器。
- 前記変調オン動作時における前記光信号の強度に対応する情報である光強度情報を記録する光強度情報保持部をさらに備えることを特徴とする請求項1から3のいずれか1項に記載の光送信器。
- 前記光強度情報保持部に記録された前記光強度情報は、前記第2の制御目標点を示すことを特徴とする請求項4に記載の光送信器。
- 前記変調オフ動作時には、前記バイアス制御部は、前記光強度情報保持部に記録された前記光強度情報を用いて前記制御目標点を切り替えることを特徴とする請求項5に記載の光送信器。
- 前記光強度検出部は、前記変調オン動作時において、前記光信号の強度を検出することにより前記光強度情報を生成して前記光強度情報保持部に送信することを特徴とする請求項4から6のいずれか1項に記載の光送信器。
- 前記変調オフ動作時には、前記バイアス制御部は、他の光変調部とは独立して、前記制御目標点を前記第1の制御目標点から前記第2の制御目標点に切り替えて前記フィードバック制御を実行することを特徴とする請求項1から7のいずれか1項に記載の光送信器。
- 前記光変調器は、マッハツェンダ変調器であることを特徴とする請求項1から8のいずれか1項に記載の光送信器。
- 連続光を出力する光源をさらに備え、
前記連続光は、前記縦列接続された1段目からN段目までの光変調部の内の1段目の光変調部の前記入力光として入力される
ことを特徴とする請求項1から9のいずれか1項に記載の光送信器。
Priority Applications (5)
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CN201480083908.1A CN107005311A (zh) | 2014-12-11 | 2014-12-11 | 光发送器 |
PCT/JP2014/082825 WO2016092666A1 (ja) | 2014-12-11 | 2014-12-11 | 光送信器 |
EP14907713.3A EP3232588A4 (en) | 2014-12-11 | 2014-12-11 | Optical transmitter |
JP2016563350A JP6261765B2 (ja) | 2014-12-11 | 2014-12-11 | 光送信器 |
US15/534,817 US10042191B2 (en) | 2014-12-11 | 2014-12-11 | Optical Transmitter |
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PCT/JP2014/082825 WO2016092666A1 (ja) | 2014-12-11 | 2014-12-11 | 光送信器 |
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EP (1) | EP3232588A4 (ja) |
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Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2018170562A (ja) * | 2017-03-29 | 2018-11-01 | 富士通株式会社 | 信号品質測定装置及び信号品質測定方法 |
US11005569B1 (en) * | 2020-08-28 | 2021-05-11 | Nokia Solutions And Networks Oy | Optical transmitter having cascaded modulators |
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Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10903908B2 (en) * | 2017-06-21 | 2021-01-26 | Mitsubishi Electric Corporation | Optical transmission apparatus, optical transmission method, control circuit of the optical transmission apparatus, and storage medium of the optical transmission apparatus |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2007208472A (ja) * | 2006-01-31 | 2007-08-16 | Fujitsu Ltd | 光送信器 |
JP2008092172A (ja) * | 2006-09-29 | 2008-04-17 | Fujitsu Ltd | 光送信機 |
JP2008249848A (ja) * | 2007-03-29 | 2008-10-16 | Fujitsu Ltd | 光変調装置および光変調方式切替方法 |
JP2010243953A (ja) * | 2009-04-09 | 2010-10-28 | Nippon Telegr & Teleph Corp <Ntt> | 送信器、及び送信方法 |
Family Cites Families (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4771067B2 (ja) * | 2005-12-01 | 2011-09-14 | 独立行政法人情報通信研究機構 | 光干渉による光スイッチシステム |
JP4910388B2 (ja) * | 2005-12-22 | 2012-04-04 | 株式会社日立製作所 | 光変調装置、光送信器、及び光伝送装置 |
US20070206960A1 (en) | 2006-03-06 | 2007-09-06 | Tyco Telecommunications (Us) Inc. | Transmission Formats for High Bit-Rate Systems |
US7733193B2 (en) * | 2007-11-01 | 2010-06-08 | Ciena Corporation | Systems and methods for DQPSK modulator control using selectively inserted dither tone |
JP2009288509A (ja) * | 2008-05-29 | 2009-12-10 | Fujitsu Ltd | 光変調装置 |
JP5476697B2 (ja) * | 2008-09-26 | 2014-04-23 | 富士通株式会社 | 光信号送信装置 |
JP5655365B2 (ja) * | 2009-08-04 | 2015-01-21 | セイコーエプソン株式会社 | 光偏向器、光偏向器の製造方法および画像表示装置 |
US20120288284A1 (en) * | 2010-02-25 | 2012-11-15 | Mitsubishi Electric Corporation | Optical transmitter |
JP5542620B2 (ja) | 2010-11-01 | 2014-07-09 | 三菱電機株式会社 | 光送信機および光通信システム |
JP5853386B2 (ja) * | 2010-12-16 | 2016-02-09 | 富士通オプティカルコンポーネンツ株式会社 | 光変調装置および光変調制御方法 |
JP5006978B1 (ja) * | 2011-03-30 | 2012-08-22 | 株式会社フジクラ | 補償方法、光変調システム、及び光復調システム |
JP5948849B2 (ja) * | 2011-12-16 | 2016-07-06 | 富士通オプティカルコンポーネンツ株式会社 | 光変調装置、及び、光変調装置における制御方法 |
JP6120761B2 (ja) * | 2013-12-12 | 2017-04-26 | 三菱電機株式会社 | 光送信器および光送信器の制御方法 |
JP6354553B2 (ja) * | 2014-12-02 | 2018-07-11 | 住友電気工業株式会社 | バイアス制御回路およびそれを含む光送信器 |
-
2014
- 2014-12-11 WO PCT/JP2014/082825 patent/WO2016092666A1/ja active Application Filing
- 2014-12-11 US US15/534,817 patent/US10042191B2/en not_active Expired - Fee Related
- 2014-12-11 JP JP2016563350A patent/JP6261765B2/ja not_active Expired - Fee Related
- 2014-12-11 CN CN201480083908.1A patent/CN107005311A/zh not_active Withdrawn
- 2014-12-11 EP EP14907713.3A patent/EP3232588A4/en not_active Withdrawn
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2007208472A (ja) * | 2006-01-31 | 2007-08-16 | Fujitsu Ltd | 光送信器 |
JP2008092172A (ja) * | 2006-09-29 | 2008-04-17 | Fujitsu Ltd | 光送信機 |
JP2008249848A (ja) * | 2007-03-29 | 2008-10-16 | Fujitsu Ltd | 光変調装置および光変調方式切替方法 |
JP2010243953A (ja) * | 2009-04-09 | 2010-10-28 | Nippon Telegr & Teleph Corp <Ntt> | 送信器、及び送信方法 |
Non-Patent Citations (1)
Title |
---|
See also references of EP3232588A4 * |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2018170562A (ja) * | 2017-03-29 | 2018-11-01 | 富士通株式会社 | 信号品質測定装置及び信号品質測定方法 |
US11005569B1 (en) * | 2020-08-28 | 2021-05-11 | Nokia Solutions And Networks Oy | Optical transmitter having cascaded modulators |
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CN107005311A (zh) | 2017-08-01 |
US10042191B2 (en) | 2018-08-07 |
EP3232588A1 (en) | 2017-10-18 |
EP3232588A4 (en) | 2018-08-15 |
JPWO2016092666A1 (ja) | 2017-05-25 |
US20170351123A1 (en) | 2017-12-07 |
JP6261765B2 (ja) | 2018-01-17 |
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