Excitable response of a noisy adaptive network of spiking lasers

We analyze experimentally and theoretically the response of a network of spiking nodes to external perturbations. The experimental system consists of an array of semiconductor lasers that are adaptively coupled through an optoelectronic feedback signal. This coupling signal can be tuned from one to all to globally coupled and makes the network collectively excitable. We relate the excitable response of the network to the existence of a separatrix in phase space and analyze the effect of noise close to this separatrix. We find numerically that larger networks are more robust to uncorrelated noise sources in the nodes than small networks, in contrast to the experimental observations. We remove this discrepancy considering the impact of a global noise term in the adaptive coupling signal and discuss our observations in relation to the network structure.