Dual-polarization carrier-assisted differential detection with asymmetric twin-SSB modulation and simplified receiver...

Area of Science:

• Optical Communications
• Signal Processing
• Photonics

Background:

• Carrier-assisted differential detection (CADD) enables high-capacity, cost-sensitive short-reach optical communications by reconstructing complex-valued double-sideband (CV-DSB) signals without a local oscillator laser.
• Existing CADD schemes face challenges in polarization fading and signal-signal beat interference (SSBI) for polarization division multiplexed (PDM) signals.

Purpose of the Study:

• To propose and validate a novel polarization division multiplexed asymmetric twin single-sideband CADD (PDM-ATSSB CADD) scheme for efficient optical field recovery of PDM CV-DSB signals.
• To develop a joint SSBI iterative mitigation algorithm to address intra- and inter-polarization SSBI.
• To evaluate the performance and potential hardware efficiency of the proposed scheme for data center interconnects.

Main Methods:

• Implementation of a PDM-ATSSB CADD receiver utilizing a pair of optical bandpass filters (OBPFs) to suppress unwanted polarization components and recover the dual-polarization optical field.
• Employment of an asymmetric twin-SSB signal to relax optical filter edge sharpness requirements.
• Development and application of a joint SSBI iterative mitigation algorithm for both intra- and inter-polarization SSBI.
• Numerical simulations to analyze parameter optimization (optical delay, iterations) and the impact of phase noise, relative intensity noise, and polarization impairments.

Main Results:

• Successful validation of the PDM-ATSSB CADD scheme for 30 Gbaud PDM asymmetric twin-SSB 16-ary quadrature amplitude modulation signals.
• Demonstrated reduction in the required frequency gap by 1 GHz compared to PDM-symmetric-TSSB CADD (PDM-STSSB CADD) to reach the 7% forward error correction (FEC) threshold.
• Achieved an improvement in OSNR sensitivity of approximately 3 dB.
• Identified simplified PDM-ATSSB CADD schemes as potentially hardware-efficient solutions.

Conclusions:

• The proposed PDM-ATSSB CADD scheme effectively recovers PDM optical fields and mitigates SSBI, offering significant performance improvements over existing methods.
• The scheme relaxes optical filter requirements and demonstrates robustness against various noise and polarization impairments.
• Simplified versions present promising, hardware-efficient candidates for metro and inter-data center interconnect applications.