Real-time optical signal equalization with a silicon photonic spatially distributed reservoir computer

Abstract

Communication through optical fibres experiences limitations due to chromatic dispersion and nonlinear Kerr effects that degrade the signal. Mitigating these impairments is typically done using complex digital signal processing algorithms. However, these equalization methods require substantial power consumption and introduce high latencies. Photonic reservoir computing (a subfield of neural networks) offers an alternative solution—processing signals in the analogue optical domain. Here we present, to our knowledge, the first experimental demonstration of the real-time equalization of fibre distortions using a silicon photonics chip that combines the recurrent reservoir and the programmable read-out layer. We successfully equalize a 28-Gbps on–off keying signal across varying power levels and fibre lengths, even in the highly nonlinear regime. We obtain bit error rates that are orders of magnitude below previously reported optical equalization methods, reaching as low as 4 × 10−7, far below the generic forward error correction limit of 5.8 × 10−5 used in commercial Ethernet interfaces.