Probabilistic shaping (PS) is a promising technique to approach the Shannon limit using typical constellation geometries. However, the impact of PS on the chain of signal processing algorithms of a coherent receiver still needs further investigation. In this work we study the interplay of PS and phase recovery using the blind phase search (BPS) algorithm, which is widely used in optical communications systems. We first investigate a supervised phase search (SPS) algorithm as a theoretical upper bound on the BPS performance, assuming perfect decisions. It is shown that PS influences the SPS algorithm, but its impact can be alleviated by moderate noise rejection window sizes. On the other hand, BPS is affected by PS even for long windows because of correlated erroneous decisions in the phase recovery scheme. The simulation results also show that the capacity-maximizing shaping is near to the BPS worst-case situation for square-QAM constellations, causing potential implementation penalties.

No abstract

No abstract

We outline our vision to introduce ground-breaking programmable spatial multiplexing in novel transceivers capable of interfacing advanced multi-mode/core fibres with hundreds of spatial pathways and enabling scalability of all data pathways to reduce the cost and energy-consumption per bit.

We assess the performance of the modified Gardner timing error detector under probabilistic shaping. The results indicate severe limitations in specific combinations of shaping and roll-off factors. The results are validated by simulations and experiments.