High-fidelity front-end response estimation and pre-compensation for bandwidth-limited coherent systems using single-pulse probing.

This paper proposes a measurement-driven pre-compensation scheme based on single-pulse (SP) probing for high-fidelity estimation of the aggregate transceiver front-end response in bandwidth-limited coherent optical systems. By exploiting the temporal isolation of a single probe pulse, the proposed scheme enables accurate characterization of fine spectral ripples under finite laser linewidth, whereas conventional sequence-based schemes tend to lose such details. Numerical simulations further quantify the phase-noise robustness by showing a nearly constant normalized mean squared error (NMSE) of about -27 dB over a total linewidth sweep from 1 kHz to 100 MHz, corresponding to more than 14 dB lower NMSE than a training-sequence-based method at 10 MHz linewidth. Experiments using 60 Gbaud PDM-16QAM over a 300-km SSMF link further demonstrate that the proposed method effectively flattens the estimated front-end frequency response, thereby restoring the matched-filter gain and providing a launch power margin improvement of 0.62 dB at the 7% HD-FEC threshold compared with a conventional sequence-based scheme.