Performance evaluation of heterodyne optical multi-carrier MFSK based on BIB design

The performance of a noncoherent heterodyne optical multi-carrier frequency shift keying (MC-MFSK) system is evaluated in the presence of laser phase noise and photodetector shot noise. Balanced incomplete block (BIB) design from combinatorial theory is utilized to reduce the number of lasers and wavelengths needed to construct the MFSK symbols. To attain the best possible performance optical heterodyne detection is employed in the receiver. Receiver performance is evaluated in terms of a union upper bound on the bit error rate (BER). A closed form expression for the union bound on the error probability conditioned on laser phase noise is obtained. The result was averaged over laser phase noise using simulation. It can be seen from the BER results that when laser phase noise is significant MC-MFSK is several dB better than conventional MFSK, owing to the implicit frequency diversity that is present in the former. This demonstrates that the effects of laser phase noise are substantially reduced due to the implicit diversity.