In case of Differential Quadrature Phase Shift Keying transmission, the diode laser frequency instability affects the quality of the received signal. Free-running transmitters are employed to experimentally evaluate the tolerance of the interferometric DQPSK receiver to this instability. Heterodyne measure of the frequency offset is discussed for different transmitters. Experimental data are related both with BER performance and power penalty. Polarization-dependent delay impairment is isolated as well.

The Resonant Router (ReR) is an integrated optics crossbar matrix based on ring resonators. Depending on the characteristics of the rings the ReR can operate as cross-connect (X-ReR) or as wavelength router (λ-ReR). The analysis of the device, the spectral characteristics and the impact on a high bit rate signal are presented and discussed both on theoretical and experimental basis. The ReR can add flexibility and extend the capabilities of a node of a transparent optical network.

The paper presents and compares various unicast nonblocking architectures to be used into space-domain photonic switching networks. All the analyzed architectures have been evaluated and compared considering a possible physical implementation based on guided-wave structures realized with integrated optics technology. Some properties including number of switching elements required, blocking performance, number of waveguide crossovers, system attenuation, and signal-to-noise ratio are evaluated and analyzed. The main purpose of this work is to review the state-of-the-art of optical guided-wave space-switching architectures and to provide a relevant set of technical elements useful in the selection of architectures to be used in all-optical cross-connect implementation.

We present a heuristic method to optimize the capacity of a WDM mesh network assigning working and protection capacity to a set of static optical-connection requests under the link-disjoint constraint. The method can be applied to networks supporting either dedicated or shared path-protection. Routing and fiber and wavelength assignment (RFWA) are jointly performed for all the lightpaths with the aim of minimizing the number of fibers in the network. The employment of multiple prioritized heuristic criteria and an efficient link disjoint paths search algorithm are proposed. With less computational effort, the proposed heuristic approach allows one to obtain good suboptimal results compared to the exact integer-linear-programming optimization. After introducing our design approach, we discuss the optimization of particular case-study networks under various conditions and compare the results.

The advantages of employing passive optical architectures in the access network have been largely recognized. Particularly, developments in optical technologies have made the realization of wavelength division multiplexing passive optical networks (WDM-PONs) feasible and cost-effective. These networks are more future-proof than conventional PONs, thanks to their intrinsic optical transparency and their extremely high transmission capacity. A very useful optical routing device, called a waveguide grating router, is the basic building-block of new PON architectures capable of connecting a large number of users or to improve the use of the optical bandwidth. In this paper the feasibility of these architectures is discussed by considering the costs and the technological limitations on the optical components.

Dynamic wavelength assignment in a WDM all-optical network with sparse wavelength conversion is discussed in this paper. The performance of unidirectional and bidirectional ring networks in terms of blocking probability, conversion gain and fairness are evaluated under various types of offered traffic patterns. Smooth and peaked patterns have been considered in addition to the classical Poisson traffic type. It is shown how the use of wavelength converters affects the blocking performance of connections and, more importantly in terms of network fairness, its dependence on the source-destination distance.