Figure 1. Reservoir computing concept and experimental scheme.

(a) Schematic representation of computation using nonlinear transient states generated by a single nonlinear element (NL) subject to delayed feedback. The N transient states x_m(t) used for computation are distributed along the delay line with spacing Θ. Here, u stands for the information input, y_k(t) for the value of the readout with index k. Panel (b) schematically shows the experimental realization of all-optical computation, utilizing a semiconductor laser diode as the nonlinear node. Information can be injected optically (electrically), given by u^(o) (u^(e)). The feedback delay is given by τ_D. The experimental setup comprises the laser diode, a tunable laser source to optically inject the information, a Mach–Zehnder modulator (MZM), a polarization controller, an attenuator, a circulator, splitters and a fast photo diode (PD) for signal detection.