Optical Phase-Locked Loop

Report
New Opportunities for Optical
Phase-locked Loops in
Coherent Photonics
Larry A. Coldren , Mingzhi Lu, Hyun-chul Park
ECE UCSB
“区域光纤通信网与新型光通信系统”国家重点实验室
Outline
Background
• Coherent Optical Communication
• Optical Frequency Synthesizer/Sweeper
Architecture of OPLL
Experiments and Results
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“区域光纤通信网与新型光通信系统”国家重点实验室
Coherent Optical Communication
Spring up in 1980s
• Coherent receiver vs. IMDD
• Improve sensitivity
• Longer reach between repeaters
• Optical homodyne: Best power penalty performance
• OPLL prototypes
• Phase error reduction/Synchronization
• LIMIT
• Laser linewidth
• Loop bandwidth
• Stability: temperature, vibration, environment fluctuations
Refrigerated in 1990s
• EDFA
• WDM
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“区域光纤通信网与新型光通信系统”国家重点实验室
Coherent Optical Communication
2000s, Digitalization
• Spectral efficiency
• Full vector optical field
• Linear, nonlinear effects introduced by long-distance propagation
• Intradyne:
• High-speed ADCs
• Sophisticated DSPs
• Complicated algorithms
• Costly to design/fabricate/operate, Power consumption
2010s, revival
• Enhanced sensitivity
• Small size, low power
• Sensor applications
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“区域光纤通信网与新型光通信系统”国家重点实验室
Optical Frequency Synthesizer/Sweeper
Optical signal processing
•
Microwave photonics:
– Microwave signal generation
– Microwave Phase Detector/Shifter
•
Military:
– Beam-forming
– LO distribution
– Up/Down Conversion
Coherent Optical Measurement and Sensing Systems
• FMCW LIDAR
• OFDR
• Ultra-accurate optical spectrum analyzers
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“区域光纤通信网与新型光通信系统”国家重点实验室
Optical Phase-Locked Loop
OPLL Concept
Optical: Laser Output
Phase-Locked: Phase error (Phase noise)
Reduction / Synchronization
Loop: Feedback
OPLL Structure
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“区域光纤通信网与新型光通信系统”国家重点实验室
OPLL: Optical Phase Detector
Phase Detector Types
• Homodyne / Heterodyne
• Linear / Nonlinear
Linear Homodyne Detection
Balanced loop
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“区域光纤通信网与新型光通信系统”国家重点实验室
OPLL: Optical Phase Detector
Other Detection Types
Costas/Decision-driven loop
SyncBit loop
Dither loop
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“区域光纤通信网与新型光通信系统”国家重点实验室
OPLL: Optical Voltage Controlled Oscillator
OVCO techniques:
•
•
Resonator mirrors tuning (by PZT)
fLO
Laser
Laser driving current
OVCO
PZT/
Current control
Vc
•
•
•
Phase modulation
Acousto-optic modulation
Laser
fLO
PM/AOM/
MZM
fLO +fVCO
fVCO
SSB modulation
Electrical
VCO
OVCO
Vc
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“区域光纤通信网与新型光通信系统”国家重点实验室
Optical Phase-Locked Loop
Requirement
•
Large loop bandwidth
–
–
•
•
•
•
•
•
•
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Bandwidth of OPD、OVCO
Short loop delay for stable operation
Narrow laser linewidth
Insensitive to environment fluctuation
Small size
Low power
No crosstalk between phase-locking signal and data
Transparent link
No residual carrier transmission required
“区域光纤通信网与新型光通信系统”国家重点实验室
Architecture of OPLL
Costas Loop
Homodyne / Heterodyne
Loop bandwidth: 1.1GHz
Phase error variance: <0.03  2
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“区域光纤通信网与新型光通信系统”国家重点实验室
Architecture of OPLL
EIC:
PIC:
• SG-DBR laser
•
90° Optical Hybrid
• LIA
• SSB Mixer
• four uni-traveling carrier PDs
• XOR and a delay line
• 4.3 × 0.56 mm2
• 1.30 × 1.20 mm2
• 40 ps propagation delay
• 50 ps propagation delay
Size: 10 × 10 mm2
Loop delay: 120 ps
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“区域光纤通信网与新型光通信系统”国家重点实验室
Architecture of OPFD
SSB Mixer
PFD
• Heterodyne
• Quadricorrelator Type
• Frequency sweep
• Pull-in range: ±46GHz
(Range:±1~20GHz)
SSB Mixer
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“区域光纤通信网与新型光通信系统”国家重点实验室
Hybrid Loop Filter
Type II 2nd Order Loop Filter
• High DC gain
• OPA delay of 200ps
Feedforward capacitor
• Phase compensation
ωn = 4.4 × 109 rad/s
Phase Margin = 65°
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“区域光纤通信网与新型光通信系统”国家重点实验室
Experiment and Result
Locking 10MHz linewidth laser to 100KHz
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“区域光纤通信网与新型光通信系统”国家重点实验室
Experiment and Result
40Gbit/s coherent receiver using costas loop
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“区域光纤通信网与新型光通信系统”国家重点实验室
Conclusion
High bandwidth
Small size and low power
Large optical frequency synthesis range
For multiple applications
• Frequency-Modulated Continuous-Wave (FMCW) Light Detection and
Ranging (LIDAR) systems
• Widely-and-fast-tunable ultra-narrow-linewidth lasers
• Ultra-accurate optical spectrum analyzers
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“区域光纤通信网与新型光通信系统”国家重点实验室
谢 谢!
“区域光纤通信网与新型光通信系统”国家重点实验室

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