R. Noé (Germany)
Intradyne detection, Homodyne detection, Optical fiber communication, Phase shift keying, Quadrature phase shift keying, Synchronous detection.
Quaternary phase shift keying (QPSK) is attractive to increase transmission lengths and capacity, especially when it is combined with polarization division multiplex. Baseband processing is required at 40Gbaud to keep the required electronic bandwidth low. So far, external cavity lasers seemed to be indispensable for such transmission systems. We propose a feedforward carrier recovery scheme based on regenerative intradyne frequency dividers, i.e., the well-known regenerative frequency divider is extended to process baseband in-phase and quadrature (I&Q) signals. An IF linewidth tolerance of up to 0.001 times the QPSK symbol rate is predicted, 2 decades more than for an optical phase locked loop with a realistic loop delay. This means that commercially available DFB lasers shall suffice.
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