Baud-rate timing phase error detector with improved timing jitter performance for self-homodyne coherent transmission

Most existing timing phase error detectors (TPEDs) for coherent systems require an oversampling factor (OSF) of two and hundreds of multiplications per operation for noise averaging, resulting in high computational complexity and significant latency. Their performance may further degrade in systems employing Nyquist pulse shaping (NPS) or probabilistic constellation shaping (PCS), while their timing jitter performance may deteriorate markedly for high-order modulation due to transitions between symbols with different levels. While self-homodyne coherent detection (SHCD) simplifies receiver digital signal processing (DSP) by inherently eliminating local oscillator frequency and phase offset, this advantage has not been fully exploited in TPED design. In this paper, we propose what we believe to be a novel baud-rate, multiplication-free TPED that leverages this advantage to eliminate the timing jitter degradation induced by symbol transitions through decision operations, thereby addressing all the aforementioned limitations. Numerical simulations and experiments based on 61 GBaud polarization division multiplexing 16QAM SHCD transmission confirm that the proposed TPED yields approximately 10 dB improvement in timing jitter performance and about 1 dB enhancement in receiver sensitivity compared with its counterpart. Furthermore, it demonstrates robust resilience against NPS and PCS. These merits underscore its promising potential for next-generation low-complexity, high-performance SHCD receivers.