In the imminent era of bandwidth-abundant optical networks, the concept of hierarchical optical network architectures emerges, decoupling the massive spatial division multiplexing (SDM) layer and the wavelength division multiplexing layer. In this paper, we perform a networking-level analysis of a generalized multiband optical cross-connect (OXC) that realizes switching in two steps: grouping wavelengths and switching them as waveband paths. The performed analysis is simulated for multiband and SDM systems, demonstrating that while conventional single-layer wavelength routing remains effective under certain conditions, waveband routing offers a more scalable and cost-effective solution under specific high-load conditions in bandwidth-abundant optical networks. This positions waveband routing as a promising alternative for future high-capacity networks.

Nowadays, optical transport and data center networks utilize wavelength-division multiplexing (WDM) and band division multiplexing (BDM) as possible solutions to increase the capacity to support the ever-increasing traffic demand. It is an alternative solution to simple spatial division multiplexing (SDM) intended to utilize more than one fiber per link. In this perspective, we propose a new modular photonic integrated multi-band wavelength selective switch (WSS) to implement a novel reconfigurable optical add-drop multiplexer (ROADM) architecture. The proposed WSS can operate on a broad spectrum range, covering the three S+C+L bands, and is potentially scalable to large numbers of output fibers and routed channels while maintaining a small footprint. We investigated the network performance assessment of the ROADM architecture based on the proposed multi-band WSS on a German network, and a detailed comparison is given for both SDM and BDM solutions. Results show that the increase in network capacity by exploiting more bands in the cost-efficient BDM scenario is quite close to the SDM scenario using existing infrastructure replicated over multiple fibers.

Modern elastic optical networking requires additional flexibility at each layer compared to the traditional approach. The application of the Software-defined Networking (SDN) paradigm can provide the required degrees of freedom. The implementation of optical SDN down to the physical layer requires the complete abstraction of network elements to support full control by the centralized controller. In this work, we propose a topological and technological agnostic model based on Machine Learning (ML) to abstract the behavior of optical switches for the computation of Quality-of-transmission (QoT) penalties and the definition of control states. Training and testing datasets are obtained synthetically by software simulation of the photonic switching structure. Results show the capability of the proposed method to predict QoT impairments with high accuracy, and we envision its application in a real-time control plane.

This paper presents Ring Optical Network (RingO), a wavelength-division-multiplexing (WDM), ring-based, optical packet network suitable for a high-capacity metro environment. We present three alternative architectural designs and elaborate on the effectiveness of optic with respect to electronic technologies, trying to identify an optimal mix. We present the design and prototyping of a simple but efficient access control protocol, based upon the equivalence of the proposed network architecture with input-buffering packet switches. We discuss the problem of node allocation to WDM channels, which can be viewed as a particular optical network design problem. We, finally, briefly illustrate the fault protection properties of the RingO architecture. The main contribution of this paper is the identification and experimental validation of an innovative optical network architecture, which is feasible and cost effective with technologies available today, and can be a valid alternative to more consolidated solutions in metro applications.

We present in this paper a novel accurate method to analyze the performance of an optical link where the amplified spontaneous emission noise, enhanced by a fiber nonlinear phenomenon called parametric gain, is the limiting factor. Our method allows us to compute the exact error probability given a generic noise spectral density at the input of a direct detection optical receiver, using arbitrary optical and electrical filters. We compare our results with those predicted using the standard Gaussian technique (based on the Q factor), showing that this approximation may lead to significant errors. Our method is then used to evaluate the impact of parametric gain on a realistic long-haul multiwavelength link operating at 10 Gb/s, showing both the system limitation imposed by this phenomenon and the inaccuracy of the Q factor method.

A novel method to evaluate the bit error rate (BER) in optical links is described. It analyzes systems limited by amplified spontaneous emission (ASE) noise, enhanced by the non-linear parametric gain (PG) effect, and allows one to compute the exact error probability, given a generic optical noise spectral density at the input of a direct detection optical receiver. The method has been employed to evaluate the impact of PG on a 10 Gb/s per channel long-haul multi-wavelength system. It has also been used to show how the system performance evaluation based on the Q-factor Gaussian approximation may lead to erroneous BER evaluations.

We study the effect of parametric gain in long-haul, optically amplified links. We started by introducing a formalism required to evaluate the spectral enhancement of amplified spontaneous emission noise due to the Kerr-effect non-linear interaction between the signal and noise. These results are then used to evaluate parametric gain-induced performance degradation on the system Q value. Finally we analyze long-haul links at 10 Gb/s using different dispersion compensation maps by evaluating the maximum reachable distance in each configuration. We show that less frequent dispersion compensation improves the system performance.

The fast-paced evolution of long-haul and high-bit-rate terrestrial and submarine optical transmission links requires powerful analysis tools that take into account all the relevant phenomena in the fiber. To provide such a tool, we developed a time-domain optical system simulation package, integrated in the TOPSIM simulation environment. The fiber simulation module makes use of the vector form of the propagation equations to account for the quasi-degenerate two-mode (the two polarizations) medium propagation characteristics. This way, all polarization-related effects and their interplay with the other linear and nonlinear phenomena in the fiber can be accurately modeled. In particular, the fiber third-order susceptivity, responsible for all major nonlinear effects, is expressed in its actual vector form, so that nonlinear polarization mode coupling could be accounted for. Conventional birefringence and PMD are generated using appropriate random models. A novel feature of the simulator is that it uses time-domain digital filters to simulate dispersion effects, as opposed to the usual FFT-based algorithms. This approach leads to more efficient computing for a wide range of bandwidth and dispersion values. We present the fiber simulation module in detail. As an example of the use of the simulation package, the analysis of a long-haul two-channel transoceanic WDM transmission system is presented.