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Receiver IQ skew tolerant baud-rate timing recovery scheme for short-reach coherent optical interconnection
Optics Letters- received 03/14/2024; accepted 04/20/2024; posted 04/22/2024; Doc. ID 523842
- Abstract: A baud-rate sampling timing recovery (TR) scheme with receiver IQ skew tolerance is proposed and experimentally demonstrated. The proposed scheme performs independent TR for the in-phase and quadrature (IQ) tributary signals, thereby tracking the sampling phase error while naturally compensating for receiver IQ skew. The robustness of the IQ-independent TR to frequency offset (FO) and phase noise is theoretically analyzed. To address IQ misalignment caused by the IQ-independent TR, the use of pseudo-noise (PN) sequences for IQ frame synchronization is proposed. The proposed scheme achieves accurate timing recovery with hardware-efficient baud-rate sampling in the presence of receiver IQ skew, laying the foundation for stable performance of subsequent baud-rate equalization. The performance of the scheme is validated in a 56 GBaud polarization division multiplexed (PDM) 16QAM coherent experimental system. Experimental results demonstrate that the proposed scheme achieves similar BER performance as the modified Gardner + RVMIMO (@2SPS) scheme. Moreover, the proposed scheme exhibits robustness to arbitrary IQ skew compared to the ABSPD + RVMIMO (@1SPS) scheme.