Optimum phase deviations between mark-and space-state bits in long-haul coherent communication systems with balanced PLL receivers

In this paper, we report the importance of the optimum phase deviation between mark-state and space-state bits in a long-haul PSK homodyne system with a balanced phase-locked-loop (PLL) receiver. The laser phase noise, data-to-phase-lock crosstalk, receiver shot noise and amplifier noise are considered in analyzing the systems with cascaded optical amplifier chains. The signal power penalty incurred by improper use of phase deviations in a long-haul system is evaluated. It is found that such power penalty can amount to larger than 1.5 dB in a 10-Gbt/sec system.<
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