Impairment-aware WDM–CPDM laser VLC with adaptive coherent DSP

Laser-based visible-light communication (VLC) can exploit wavelength and polarization multiplexing, but amplifier, channel, and coherent-receiver impairments interact. This paper develops an impairment-aware simulation of an eight-wavelength, dual-circular-polarization link carrying a 380.16-MHz occupied orthogonal frequency-division multiplexing (OFDM) resource grid within a nominal 400-MHz fifth-generation New Radio (5G NR)-aligned channel. The model includes laser-diode/semiconductor-optical-amplifier (LD–SOA) saturation and amplified spontaneous emission, wavelength-dependent gain ripple, Lambertian line-of-sight loss, residual wavelength-division-multiplexing (WDM) crosstalk, polarization mixing, coherent-receiver noise, phase/frequency offsets, and quadrature imbalance. The receiver combines covariance whitening, pilot-estimated 2 × 2 regularized multiple-input multiple-output (MIMO) separation, pilot-assisted phase correction, and damped decision-directed refinement. With quadrature phase-shift keying, the nominal net payload rate after applying a 7 % FEC-overhead factor for rate reporting is 8.527 Gb/s. In the controlled reference realization, the proposed receiver remains below the 3.8 × 10 −3 pre-FEC bit-error-rate screening level through 50 m. A receiver ablation shows that both Gram–Schmidt orthogonalization and symmetric covariance whitening remove most of the reference I/Q-imbalance penalty, while the decision-directed update provides a smaller incremental improvement near the reach boundary. A separate sweep gives 17.054 Gb/s with 16-level quadrature-amplitude modulation through 16 m. The results provide a traceable baseline for joint optical-front-end and coherent-receiver design.