Phase modulation improves performance of delay-based reservoir computing with semiconductor lasers

In photonic reservoir computing, semiconductor lasers with delayed feedback have shown to be suited to efficiently solve difficult and time consuming
problems. The input data in this system is often optically injected into the reservoir Based on numerical simulations, we show that the performance
depends heavily on the way that information is encoded in this optical injection signal. In our simulations we compare different input configurations
consisting of Mach Zehnder modulators and phase modulators for injecting the signal. We observe far better performance on a one step ahead time
series prediction task when modulating the phase of the injected signal rather than only modulating its amplitude.