Cascaded Micro-Ring Resonator Based Reservoir Computing for Optical Equalization of PAM-4 Short Reach Signals

This study presents a photonic reservoir computer based on cascaded micro-ring resonators and numerically investigates its application to signal equalization in a short-reach, wavelength-division multiplexing fiber-optic transmission system operating in the O-band at 112 GBd. In comparison to feed-forward equalization with an equivalent level of complexity in the digital domain with identical sampling rates, the reservoir computer is capable of reducing the bit-error ratio tenfold with the same receiver requirements and numbers of photo diodes. It is demonstrated that signal equalization based on this method is tolerant to changes in received optical power and of the transmission system as well as to manufacturing deviation in the radius and coupling zones of the reservoir computer photonic integrated circuit.