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Performance and Complexity of Digital Clock Recovery for Nyquist UDWDM-PON in Real-Time

We analyze the performance and complexity of a realtime DSP-based ONU architecture for digitaldetection of Nyquist shaped signals in UDWDM-PON scenarios. Using FPGA-based 8-bit DSP, we experimentally demonstrate in a realtime mode operation the receiver performance in terms of Nyquist filter roll-off factor for 8×2.5 Gb/s QPSK with 2.5 GHz of channel spacing.

We analyze the performance of the linear and cubic interpolation for the clock recovery as well as the Gardner algorithm for timing-error estimation considering amplitude and power formulations. The experimental evaluation shows that the linear interpolation along with the power formulation is an attractive solution for QPSK-based UDWDM-PON, considering the tradeoff between performance and complexity.