Integrated coherent optical receiver with feed-forward carrier recovery

Area of Science:

• Optoelectronics
• Optical Communications
• Integrated Photonics

Background:

• Coherent optical communication demands precise phase locking between the local oscillator and incoming signal.
• Traditional receivers often rely on complex phase-locked loops and high-speed analog-to-digital converters (ADCs).

Purpose of the Study:

• To propose and demonstrate a novel coherent optical receiver architecture.
• To reduce power consumption and backend digital signal processing (DSP) complexity.
• To achieve high-speed data recovery without a phase-locked loop.

Main Methods:

• Utilizing a semiconductor laser (SCL) as the optical local oscillator.
• Employing a balanced photodiode for instantaneous phase detection.
• Implementing a feed-forward scheme to control the SCL phase.
• Integrating photonic devices on a silicon-on-insulator (SOI) platform.

Main Results:

• Demonstrated a low-power coherent optical receiver prototype.
• Achieved clock and data recovery at 10 GBaud/s.
• Obtained bit-error-rates (BER) below 10^-6 for BPSK and 10^-3 for QPSK.
• The photonic integrated circuit occupied a 1.0 mm × 0.8 mm footprint.

Conclusions:

• The proposed feed-forward phase control scheme effectively recovers input carriers.
• The novel architecture eliminates the need for a phase-locked loop and high-rate ADC.
• This approach significantly lowers the complexity and power requirements of coherent optical receivers.