MAP detection for impairment compensation in coherent WDM systems

Area of Science:

• Optical communications
• Signal processing

Background:

• Coherent wavelength division multiplexing (CoWDM) systems face challenges with inter-sub-channel crosstalk and chromatic dispersion (CD).
• Existing CoWDM systems often require complex phase control and stringent spectral design for demultiplexing filters.

Purpose of the Study:

• To introduce a novel recursive-algorithm based maximum a posteriori probability (MAP) detector for spectrally-efficient CoWDM systems.
• To evaluate the performance of the MAP detector in a 1-bit/s/Hz on-off keyed (OOK) system, focusing on optical signal-to-noise ratio limitations.

Main Methods:

• Developed a recursive-algorithm based MAP detector.
• Simulated a five-channel OOK-based CoWDM system operating at 10 Gbit/s per channel.
• Investigated performance using both direct and coherent detection methods.

Main Results:

• The MAP detector effectively compensates for deterministic inter-sub-channel crosstalk and inter-symbol interference caused by narrow-band filtering and CD.
• Eliminates the necessity for optical carrier phase control, simplifying system architecture.
• Significantly enhances back-to-back sensitivity and tolerance to chromatic dispersion.

Conclusions:

• The proposed MAP detector offers a robust solution for improving CoWDM system performance.
• Reduces complexity in receiver design by relaxing spectral requirements for demultiplexing filters.
• Paves the way for more efficient and resilient optical communication systems.