To achieve the maximum information transfer and face a possible eavesdropper, the samples transmitted in continuous-variable quantum key distribution (CV-QKD) protocols are to be drawn from a continuous Gaussian distribution. As a matter of fact, in practical implementations the transmitter has a finite (power) dynamics and the Gaussian sampling can be only approximated. This requires the quantum protocols to operate at small powers. In this paper, we show that a suitable probabilistic amplitude shaping of a finite set of symbols allows to approximate at will the optimal channel capacity also for increasing average powers. We investigate the feasibility of this approach in the framework of CV-QKD, propose a protocol employing discrete quadrature amplitude modulation assisted with probabilistic amplitude shaping, and we perform the key generation rate analysis assuming a wiretap channel and lossless homodyne detection.

We propose a new method for network authentication, identification, and secure communication, using the optical physical unclonable function Challenge-Response (PUF-CRPs) database protocol. We investigated the database performance generated with the proposed protocol by identifying 150 networks ID. Different methods and strategies for generating and exerting PUF-based CRP databases are proposed and numerically validated. The proposed method may find applications for identification and security networks with different architectures.

In flexi-grid optical networks, effective defragmentation (i.e., re-optimization) solutions are required to efficiently exploit network spectrum resources. However, current defragmentation solutions can only be implemented thanks to the presence of additional resources, such as spare extensive transponders. In this study, focusing on optically-amplified direct-detection systems, we experimentally demonstrate the feasibility of a novel defragmentation technique, called push-pull, based on dynamic lightpath frequency retuning upon proper reconfiguration of allocated spectrum resources. The technique does not require additional transponders and does not determine traffic disruption. All the relevant technological limitations that may affect the push-pull applicability are discussed. A simple yet effective closed-form expression is also proposed and experimentally validated to assess the maximum retuning range in a single push-pull operation, such that the quality of transmission during defragmentation is safely guaranteed. The technique is then successfully demonstrated in a flexi-grid network testbed. In particular the reoptimization of one lightpath is safely completed in few seconds (mainly due just to node configuration latencies) without experiencing any traffic disruption.

We present numerical results relative to a bistable optical device comprised of an asymmetric Fabry-Perot cavity embedding a nonlinear optical medium. Both the real and imaginary part of the third order nonlinear susceptibility are considered in our calculations. Optimized device operation, expressed in terms of the contrast ratio between the two stable states, is then discussed as a function of the different cavity parameters. The presented method can be a useful tool for designing practical devices with application in the field of all-optical switching, optical regeneration and optical signal processing.

Future interconnection networks will be required to achieve ultra-high bandwidth and low latency communications to cope with the increasing performance requirements of backbone routers, large data storage systems and supercomputing systems. Aiming at achieving ultra-high bandwidth communications and approaching optical time-of-flight processing latency while being robust to cascade impairments, the authors propose an all-optical packet-switched interconnection network, where not only the actual packet switching but also the packet processing is performed in the photonic domain. The authors present two modular architectures, based on the crossbar and the Batcher–Banyan topologies, capable of forwarding fixed-length packets with two classes of service. Both use photonic digital-processing subsystems built by combining a single integrable module which exploits cross gain modulation in a semiconductor optical amplifier. System level simulations on the crossbar switch controller guarantee that the control signals maintain an acceptable quality during the processing. Moreover, the Batcher–Banyan configuration is more cost-effective than the crossbar for increasing port count, while effective network performance in terms of packet loss rate can be obtained by adding just few recirculating delay lines.