Fiber-length agnostic all-optical equalisation using silicon photonics neural networks

Signal integrity in high-speed intensity-modulation direct-detection (IM/DD) fibre links is limited by chromatic dispersion, Kerr-induced nonlinearities, and the frequency-dependent response of the transmitter–receiver chain. We demonstrate an integrated photonic reservoir with a programmable optical readout for pre-detection equalisation of a 28 Gbps on–off keying (OOK) signal. Using a fixed reservoir architecture and delay configuration, experimental bit-error rates as low as 4×10-7 are achieved, remaining below the generic forward-error-correction (GFEC) threshold of 5.8×10-5 for fibre lengths up to 50 km at a launch power of 10 dBm and launch powers up to 17 dBm at a fiber length of 25 km. Numerical simulations are used to assess the impact of data-rate mismatch relative to the reservoir design point. Robust performance is obtained without reconfiguration of the photonic hardware, requiring only optimisation of the readout weights for different operating conditions.