A New OEO Design Using Optical Phase Modulation and Modulation Suppression G. John Dick and Nan Yu Jet Propulsion Laboratory, California Institute of Technology Pasadena, CA 91109-8099, U.S.A.

OEO Design Using Optical Phase Modulation Suppression Abstract We present the design for an Opto-Electronic Oscillator (OEO) using asymmetric Mach-Zehnder (AMZ) interferometers as phase demodulators together with PM modulation suppression. The new design promises to obtain in the electro-optical domain the low-noise advantages presently achieved in RF and microwave oscillators by the use of carrier suppression. OEO designs using RF carrier suppression have already been demonstrated, and they do show the rejection of amplifier flicker noise as is shown in microwave oscillator and interferometer applications [2]. However, a second important advantage of microwave carrier suppression, the reduction of the effects of thermal- or shot-noise [3], has not been realized in an OEO application before now. This second reduction is made possible in microwave applications by the use of higher power levels in the oscillator or interferometer than can be tolerated by a low-noise follower amplifier, combined with a means for reducing the power at the detector that still preserves the system’s sensitivity – i.e. without reducing the output response to phase variation induced by the resonator discriminator or component under test.

OEO Design Using Optical Phase Modulation Suppression The design presented here realizes this second advantage for the first time in the opto-electronic arena by enabling the effective use of high optical power levels to reduce shot-noise induced frequency variation in an OEO. This is done by use of an AMZ phase demodulator (phase detector) with unbalanced outputs together with modulation suppression. With appropriate delays and phases, the AMZ transmits virtually all of the optical power to a terminated output port while a signal with suppressed optical carrier but with high sensitivity to input PM is developed at the other port. Sideband amplitude also is reduced before detection by use of a phase “un-modulator” (matched to a PM modulator that replaces the AM unit used in a typical OEO). This reduction of both carrier and sidebands combines to prevent overload of the low-noise optical detector (which always has a low optical saturation power) as optical power is increased.

ʃ ʃ MSOEO Laser PM PM A Phase-Modulated OEO 2  Modulation- suppressed Optical Signal Fiber-Optic Delay Line Phase-Modulated Optical Signals Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control Laser PM PM AMZ Phase Demodulator 3 dB Power Amplifier A Phase-Modulated OEO 2  MSOEO Tuning ʃ Y OEO Tuning Signal Modulation-suppressed Noise Reduction System 3 X-Y mixer 20 dB X ʃ RF B = bright port D = dark port optical baseband MSOEO

ʃ ʃ ʃ MSOEO Laser PM PM Bias Tee  1 A Phase-Modulated OEO 2  Modulation- suppressed Optical Signal Fiber-Optic Delay Line Phase-Modulated Optical Signals Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control Laser PM PM AMZ Phase Demodulator with Balanced Level Control and Combined Outputs D 3 dB B Photo- diodes  Bias Tee  dc ʃ 1 rf AMZ Phase Demodulator 3 dB Power Amplifier A Phase-Modulated OEO 2  MSOEO Tuning ʃ Y OEO Tuning Signal Modulation-suppressed Noise Reduction System 3 X-Y mixer 20 dB X ʃ RF B = bright port D = dark port optical baseband MSOEO

AMZ Phase Demodulator with Balanced Level Control and Combined Outputs D 3 dB B Photo- diodes  Bias Tee  dc ʃ 1 rf Modulation- suppressed Optical Signal Fiber-Optic Delay Line Phase-Modulated Optical Signals Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control Laser PM PM AMZ Phase Demodulator with Balanced Level Control and Combined Outputs D 3 dB B Photo- diodes  Bias Tee  dc ʃ 1 rf AMZ Phase Demodulator 3 dB Power Amplifier A Phase-Modulated OEO 2  MSOEO Tuning ʃ Y OEO Tuning Signal Modulation-suppressed Noise Reduction System 3 X-Y mixer 20 dB X ʃ RF B = bright port D = dark port optical baseband MSOEO

AMZ Phase Demodulator with Balanced Level Control and 3 dB B Photo- diodes  Bias Tee  dc ʃ 1 rf AMZ Phase Demodulator with Balanced Level Control and Combined Outputs

ʃ  AMZ Phase Demodulator with Balanced Level Control and Phase-Modulated Optical Input AMZ Phase Demodulator with Balanced Level Control and Combined Outputs Asymmetric Mach-Zehnder Interferometer with Arm length difference L  RF / 2 and Electro-Optic or Thermal Optical Phase Control  RF Bias Tee ʃ Integrating Amplifier Photo- diodes RF Output Signal Optical Phase Control Loop keeps equal power levels at the two Detectors by Balancing Photo-Diode dc Bias levels RF Outputs Combined in 3dB Hybrid dc Bias Tee  Bright Port  RF Dark Port 3 dB

ʃ  Bias Tee dc AMZ Phase Demodulator with Balanced Level Control and Photo- diodes  Bias Tee  dc ʃ  RF 3 dB Phase-Modulated Optical Input Output Signal AMZ Phase Demodulator with Balanced Level Control and Combined Outputs Asymmetric Mach-Zehnder Interferometer with Arm length difference L  RF / 2 and Electro-Optic or Thermal Optical Phase Control RF Outputs Combined in 3dB Hybrid Integrating Amplifier Dark Port Bright Port Optical Phase Control Loop keeps equal power levels at the two Detectors by Balancing Photo-Diode dc Bias levels Photo- diodes  Phase-Modulated Optical Input AMZ Phase Demodulator with Balanced Outputs Asymmetric Mach-Zehnder Interferometer with Arm length difference L  RF / 2 and Optical Phase Control

AMZ Phase Demodulator with Asymmetric Mach-Zehnder Phase-Modulated Optical Input AMZ Phase Demodulator with Balanced Outputs Photo- diodes  Asymmetric Mach-Zehnder Interferometer with Arm length difference L  RF / 2 and Optical Phase Control

AMZ Phase Demodulator with Balanced Outputs AMZ Phase Demodulator with Photo- diodes  Phase-Modulated Optical Input AMZ Phase Demodulator with Balanced Outputs Asymmetric Mach-Zehnder Interferometer with Arm length difference L  RF / 2 and Optical Phase Control Photo- diodes  Phase-Modulated Optical Input AMZ Phase Demodulator with Balanced Outputs Asymmetric Mach-Zehnder Interferometer with Arm length difference L  RF / 2 and Optical Phase Control

AMZ Phase Demodulator with Balanced Outputs AMZ Phase Demodulator with Photo- diodes  Phase-Modulated Optical Input AMZ Phase Demodulator with Balanced Outputs Asymmetric Mach-Zehnder Interferometer with Arm length difference L  RF / 2 and Optical Phase Control Photo- diodes  Phase-Modulated Optical Input AMZ Phase Demodulator with Balanced Outputs F0 + FRF F0 - FRF F0 PM Carrier, Upper and Lower Sidebands, and Resulting Phasor at Input

AMZ Phase Demodulator with Balanced Outputs PM Carrier, Upper and Lower Sidebands, and Resulting Phasor at Input Phase-Modulated Optical Input AMZ Phase Demodulator with Balanced Outputs Photo- diodes  F0 + FRF F0 - FRF F0

AMZ Phase Demodulator with Balanced Outputs PM Carrier, Upper and Lower Sidebands, and Resulting Phasor at Input Phase-Modulated Optical Input AMZ Phase Demodulator with Balanced Outputs Photo- diodes  F0 + FRF F0 - FRF F0

AMZ Phase Demodulator with Balanced Outputs PM Carrier, Upper and Lower Sidebands, and Resulting Phasor at Input Phase-Modulated Optical Input AMZ Phase Demodulator with Balanced Outputs Photo- diodes  F0 + FRF F0 - FRF F0 F0 + FRF F0 - FRF F0

AMZ Phase Demodulator with Balanced Outputs Phase-Modulated Optical Input Photo- diodes  PM Spectral Components and Resulting Phasor at Left Branch PM Spectral Components and Resulting Phasor at Right Branch F0 + FRF F0 - FRF F0 F0 + FRF F0 - FRF F0

AMZ Phase Demodulator with Balanced Outputs Phase-Modulated Optical Input Photo- diodes  PM Spectral Components and Resulting Phasor at Left Branch PM Spectral Components and Resulting Phasor at Right Branch F0 + FRF F0 - FRF F0 F0 + FRF F0 - FRF F0

AMZ Phase Demodulator with Balanced Outputs Phase-Modulated Optical Input Photo- diodes  PM Spectral Components and Resulting Phasor at Left Branch PM Spectral Components and Resulting Phasor at Right Branch F0 + FRF F0 - FRF F0 F0 + FRF F0 - FRF F0

AMZ Phase Demodulator with Balanced Outputs Phase-Modulated Optical Input Photo- diodes  PM Spectral Components and Resulting Phasor at Left Branch PM Spectral Components and Resulting Phasor at Right Branch F0 + FRF F0 - FRF F0 F0 + FRF F0 - FRF F0

AMZ Phase Demodulator with Balanced Outputs Phase-Modulated Optical Input Photo- diodes  

AMZ Phase Demodulator with Balanced Outputs Phase-Modulated Optical Input Photo- diodes 

AMZ Phase Demodulator with Balanced Outputs Phase-Modulated Optical Input 

AMZ Phase Demodulator with Balanced Outputs Phase-Modulated Optical Input 

AMZ Phase Demodulator with Balanced Outputs Phase-Modulated Optical Input 

AMZ Phase Demodulator with Balanced Outputs Phase-Modulated Optical Input 

AMZ Phase Demodulator with Balanced Outputs Phase-Modulated Optical Input 

AMZ Phase Demodulator with Balanced Outputs Phase-Modulated Optical Input  Time  Diode Voltage Photo- diodes

AMZ Phase Demodulator with Balanced Outputs Phase-Modulated Optical Input   Time  Diode Voltage Photo- diodes

AMZ Phase Demodulator with Balanced Outputs Phase-Modulated Optical Input Photo- diodes 

ʃ  AMZ Phase Demodulator with Balanced Level Control and Phase-Modulated Optical Input AMZ Phase Demodulator with Balanced Level Control and Combined Outputs Asymmetric Mach-Zehnder Interferometer  RF Integrating Amplifier for Optical Phase Control Loop Bias Tee ʃ Photo- diodes RF Output Signal Matching the Photo-Diode dc Bias Output also gives Matched RF Output Levels dc RF Outputs Combined in 3dB Hybrid Bias Tee  Bright Port  RF RF Phase Shifter Compensates Cable Length Discrepancy and the 180 Degree Phase Difference Between Photo-Diode Outputs Dark Port Terminated 3 dB

ʃ  AMZ Phase Demodulator with Balanced Level Control and Phase-Modulated Optical Input AMZ Phase Demodulator with Balanced Level Control and Combined Outputs Asymmetric Mach-Zehnder Interferometer  RF Integrating Amplifier for Optical Phase Control Loop Bias Tee ʃ Photo- diodes RF Output Signal Matching the Photo-Diode dc Bias Output also gives Matched RF Output Levels dc RF Outputs Combined in 3dB Hybrid Bias Tee  Bright Port  RF RF Phase Shifter Compensates Cable Length Discrepancy and the 180 Degree Phase Difference Between Photo-Diode Outputs Dark Port Terminated 3 dB

AMZ Phase Demodulator with Balanced Level Control and Combined Outputs Photo- diodes  Bias Tee  dc ʃ  RF 3 dB

AMZ Phase Demodulator with Balanced Level Control and Combined Outputs D 3 dB B Photo- diodes  Bias Tee  dc ʃ 1 rf

ʃ ʃ ʃ ʃ MSOEO Bias Tee + Level Laser PM PM Bias Tee  1 A D Photodiode Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control  Bias Tee + Level dc ʃ Modulation- suppressed Optical Signal Fiber-Optic Delay Line Phase-Modulated Optical Signals Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control Laser PM PM AMZ Phase Demodulator with Balanced Level Control and Combined Outputs D 3 dB B Photo- diodes  Bias Tee  dc ʃ 1 rf AMZ Phase Demodulator 3 dB Power Amplifier A Phase-Modulated OEO 2  MSOEO Tuning ʃ Y OEO Tuning Signal Modulation-suppressed Noise Reduction System 3 X-Y mixer 20 dB X ʃ RF B = bright port D = dark port optical baseband MSOEO

ʃ ʃ ʃ ʃ MSOEO + Level Bias Tee Bias Tee + Level Laser PM PM A D Photodiode Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control  + Level dc ʃ Bias Tee B D Photodiode Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control  Bias Tee + Level dc ʃ Modulation- suppressed Optical Signal Fiber-Optic Delay Line Phase-Modulated Optical Signals Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control Laser PM PM AMZ Phase Demodulator 3 dB Power Amplifier A Phase-Modulated OEO 2  MSOEO Tuning ʃ Y OEO Tuning Signal Modulation-suppressed Noise Reduction System 3 X-Y mixer 20 dB X ʃ RF B = bright port D = dark port optical baseband MSOEO

ʃ Bias Tee + Level  B D Photodiode dc Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control B D Photodiode  + Level dc ʃ Bias Tee

ʃ Asymmetric Mach-Zehnder Demodulator with Unbalanced Outputs and Dark Port Level Control Asymmetric Mach-Zehnder Interferometer with Arm length difference L  RF / 2 and Optical Phase Control High-Power Modulation-suppressed Optical Input  Bright Port Output Terminated ʃ Integrating Amplifier Dark Port Photo- diode Optical Phase Control Loop Keeps Dark Port power level at Appropriate Level for Detector by Sensing Photo-diode dc Bias dc Bias Tee + Level RF Output Signal

ʃ Asymmetric Mach-Zehnder Demodulator with Unbalanced Outputs and Dark Port Level Control Asymmetric Mach-Zehnder Interferometer with Arm length difference L  RF / 2 and Optical Phase Control High-Power Modulation-suppressed Optical Input  Bright Port Output Terminated ʃ Integrating Amplifier Dark Port Photo- diode Optical Phase Control Loop Keeps Dark Port power level at Appropriate Level for Detector by Sensing Photo-diode dc Bias dc Bias Tee + Level RF Output Signal

AMZ Phase Demodulator with Unbalanced Outputs High-Power Modulation-suppressed Optical Input Asymmetric Mach-Zehnder Interferometer with Arm length difference L  RF / 2 and Optical Phase Control Bright Port Dark Port Photo- diode 

AMZ Phase Demodulator with Modulation-suppressed Unbalanced Outputs  High-Power Modulation-suppressed Optical Input Bright Port Dark Port

AMZ Phase Demodulator with Modulation-suppressed Unbalanced Outputs  High-Power Modulation-suppressed Optical Input Bright Port Dark Port Port Amplitude Time 

AMZ Phase Demodulator with Modulation-suppressed Unbalanced Outputs  High-Power Modulation-suppressed Optical Input Bright Port Dark Port

AMZ Phase Demodulator with Modulation-suppressed Unbalanced Outputs  High-Power Modulation-suppressed Optical Input Bright Port Dark Port Port Amplitude Time 

ʃ Asymmetric Mach-Zehnder Demodulator with Unbalanced Outputs and Dark Port Level Control Asymmetric Mach-Zehnder Interferometer with Arm length difference L  RF / 2 and Optical Phase Control High-Power Modulation-suppressed Optical Input  Bright Port Output Terminated ʃ Integrating Amplifier Dark Port Photo- diode Optical Phase Control Loop Keeps Dark Port power level at Appropriate Level for Detector by Sensing Photo-diode dc Bias dc Bias Tee + Level RF Output Signal

ʃ Asymmetric Mach-Zehnder Demodulator with Unbalanced Outputs and Dark Port Level Control Asymmetric Mach-Zehnder Interferometer with Arm length difference L  RF / 2 and Optical Phase Control High-Power Modulation-suppressed Optical Input  Bright Port Output Terminated ʃ Integrating Amplifier Dark Port Photo- diode Optical Phase Control Loop Keeps Dark Port power level at Appropriate Level for Detector by Sensing Photo-diode dc Bias dc Bias Tee + Level RF Output Signal

Asymmetric Mach-Zehnder Unbalanced Outputs and Dark Port Level Control Demodulator with Unbalanced Outputs and Dark Port Level Control  Bright Port Output Terminated ʃ Dark Port Photo- diode dc Bias Tee + Level RF Output Signal

ʃ dc Bias Tee Level  + Bright Port Output Terminated Dark Port Photo- diode  Bias Tee + Level dc ʃ RF Output Signal

ʃ ʃ ʃ ʃ MSOEO + Level Bias Tee Bias Tee + Level Laser PM PM A D Photodiode Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control  + Level dc ʃ Bias Tee B D Photodiode Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control  Bias Tee + Level dc ʃ Modulation- suppressed Optical Signal Fiber-Optic Delay Line Phase-Modulated Optical Signals Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control Laser PM PM AMZ Phase Demodulator 3 dB Power Amplifier A Phase-Modulated OEO 2  MSOEO Tuning ʃ Y OEO Tuning Signal Modulation-suppressed Noise Reduction System 3 X-Y mixer 20 dB X ʃ RF B = bright port D = dark port optical baseband MSOEO

ʃ ʃ MSOEO Laser PM PM A Phase-Modulated OEO 2  Modulation- Suppressed Optical Signal Fiber-Optic Delay Line Phase-Modulated Optical Signals Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control Laser PM PM AMZ Phase Demodulator 3 dB Power Amplifier A Phase-Modulated OEO 2  MSOEO Tuning ʃ Y OEO Tuning Signal Modulation-suppressed Noise Reduction System 3 X-Y mixer 20 dB X ʃ RF B = bright port D = dark port optical baseband MSOEO

ʃ ʃ MSOEO PM A 2 Modulation-suppressed Noise Reduction X-Y System Optical Signal Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control PM A 2 MSOEO Tuning ʃ Y Modulation-suppressed Noise Reduction System 3 X-Y mixer 20 dB X ʃ RF B = bright port D = dark port optical baseband MSOEO

ʃ PM A 2 Modulation-suppressed Noise Reduction X-Y System mixer 3 Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control 2 A 3 20 dB ʃ B = bright port D = dark port optical RF baseband Modulation- suppressed Optical Signal X-Y mixer X Y PM Modulation-suppressed Noise Reduction System MSOEO Tuning

Modulation-suppressed Optical Signal Asymmetric Mach-Zehnder Phase Demodulator PM A 2 MSOEO Tuning ʃ Y 3 X-Y mixer Modulation-suppressed Noise Reduction System 20 dB X ʃ OEO Tuning Signal RF B = bright port D = dark port optical baseband MSOEO

Modulation-suppressed Optical Signal Applied PM Modulation Asymmetric Mach-Zehnder Phase Demodulator PM A 2 MSOEO Tuning ʃ Y 3 X-Y mixer Modulation-suppressed Noise Reduction System 20 dB X ʃ OEO Tuning Signal RF B = bright port D = dark port optical baseband MSOEO

Modulation-suppressed Optical Signal Applied PM Modulation Asymmetric Mach-Zehnder Phase Demodulator PM A 2 MSOEO Tuning ʃ Y 3 X-Y mixer Modulation-suppressed Noise Reduction System 20 dB X ʃ OEO Tuning Signal RF B = bright port D = dark port optical baseband MSOEO

Modulation-suppressed Optical Signal Applied PM Modulation Asymmetric Mach-Zehnder Phase Demodulator PM A 2 MSOEO Tuning ʃ Y 3 X-Y mixer Modulation-suppressed Noise Reduction System 20 dB X ʃ OEO Tuning Signal RF B = bright port D = dark port optical baseband MSOEO

Modulation-suppressed Optical Signal Applied PM Modulation Asymmetric Mach-Zehnder Phase Demodulator PM A 2 MSOEO Tuning ʃ Y 3 X-Y mixer Modulation-suppressed Noise Reduction System 20 dB X ʃ OEO Tuning Signal RF B = bright port D = dark port optical baseband MSOEO

Modulation-suppressed Optical Signal Applied PM Modulation Asymmetric Mach-Zehnder Phase Demodulator PM A 2 MSOEO Tuning ʃ Y 3 X-Y mixer Modulation-suppressed Noise Reduction System 20 dB X ʃ OEO Tuning Signal RF B = bright port D = dark port optical baseband MSOEO

Modulation-suppressed Optical Signal Applied PM Modulation Asymmetric Mach-Zehnder Phase Demodulator PM A 2 MSOEO Tuning ʃ Y 3 X-Y mixer Modulation-suppressed Noise Reduction System 20 dB X ʃ OEO Tuning Signal RF B = bright port D = dark port optical baseband MSOEO

Modulation-suppressed Optical Signal Applied PM Modulation Asymmetric Mach-Zehnder Phase Demodulator PM A 2 MSOEO Tuning ʃ Y 3 X-Y mixer Modulation-suppressed Noise Reduction System 20 dB X ʃ OEO Tuning Signal RF B = bright port D = dark port optical baseband MSOEO

Modulation-suppressed Optical Signal Applied PM Modulation Asymmetric Mach-Zehnder Phase Demodulator PM A 2 MSOEO Tuning ʃ Y 3 X-Y mixer Modulation-suppressed Noise Reduction System 20 dB X ʃ OEO Tuning Signal RF B = bright port D = dark port optical baseband MSOEO

Modulation-suppressed Optical Signal Applied PM Modulation Asymmetric Mach-Zehnder Phase Demodulator PM A 2 MSOEO Tuning ʃ Y 3 X-Y mixer Modulation-suppressed Noise Reduction System 20 dB X ʃ OEO Tuning Signal RF B = bright port D = dark port optical baseband MSOEO

Modulation-suppressed Optical Signal Applied PM Modulation Asymmetric Mach-Zehnder Phase Demodulator PM A 2 MSOEO Tuning ʃ Y 3 X-Y mixer Modulation-suppressed Noise Reduction System 20 dB X ʃ OEO Tuning Signal RF B = bright port D = dark port optical baseband MSOEO

Modulation-suppressed Optical Signal Applied PM Modulation Asymmetric Mach-Zehnder Phase Demodulator PM A 2 MSOEO Tuning ʃ Y 3 X-Y mixer Modulation-suppressed Noise Reduction System 20 dB X ʃ OEO Tuning Signal RF B = bright port D = dark port optical baseband MSOEO

Modulation-suppressed Optical Signal Applied PM Modulation Asymmetric Mach-Zehnder Phase Demodulator PM A 2 MSOEO Tuning ʃ Y 3 X-Y mixer Modulation-suppressed Noise Reduction System 20 dB X ʃ OEO Tuning Signal RF B = bright port D = dark port optical baseband MSOEO

Modulation-suppressed Optical Signal Asymmetric Mach-Zehnder Phase Demodulator PM A 2 MSOEO Tuning ʃ Y 3 X-Y mixer Modulation-suppressed Noise Reduction System 20 dB X ʃ OEO Tuning Signal RF B = bright port D = dark port optical baseband MSOEO

ʃ ʃ ʃ ʃ MSOEO Bias Tee + Level Laser PM PM Bias Tee  1 A D Photodiode Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control  Bias Tee + Level dc ʃ Modulation- suppressed Optical Signal Fiber-Optic Delay Line Phase-Modulated Optical Signals Asymmetric Mach-Zehnder Phase Demodulator with Unbalanced Outputs and Dark Port Level Control Laser PM PM AMZ Phase Demodulator with Balanced Level Control and Combined Outputs D 3 dB B Photo- diodes  Bias Tee  dc ʃ 1 rf AMZ Phase Demodulator 3 dB Power Amplifier A Phase-Modulated OEO 2  MSOEO Tuning ʃ Y OEO Tuning Signal Modulation-suppressed Noise Reduction System 3 X-Y mixer 20 dB X ʃ RF B = bright port D = dark port optical baseband MSOEO