The Grid 2: Blueprint for a New Computing Infrastructure

Orthogonal Frequency Division Multiplexing (OFDM) has recently been proposed as a modulation technique for optical networks, because of its good spectral efficiency, flexibility, and tolerance to impairments. We consider the planning problem of an OFDM optical network, where we are given a traffic matrix that includes the requested transmission rates of the connections to be served. Connections are provisioned for their requested rate by elastically allocating spectrum using a variable number of OFDM subcarriers and choosing an appropriate modulation level, taking into account the transmission distance. We introduce the Routing, Modulation Level and Spectrum Allocation (RMLSA) problem, as opposed to the typical Routing and Wavelength Assignment (RWA) problem of traditional WDM networks, prove that is also NP-complete and present various algorithms to solve it. We start by presenting an optimal ILP RMLSA algorithm that minimizes the spectrum used to serve the traffic matrix, and also present a decomposition method that breaks RMLSA into its two substituent subproblems, namely 1) routing and modulation level and 2) spectrum allocation (RML+SA), and solves them sequentially. We also propose a heuristic algorithm that serves connections one-by-one and use it to solve the planning problem by sequentially serving all the connections in the traffic matrix. In the sequential algorithm, we investigate two policies for defining the order in which connections are considered. We also use a simulated annealing meta-heuristic to obtain even better orderings. We examine the performance of the proposed algorithms through simulation experiments and evaluate the spectrum utilization benefits that can be obtained by utilizing OFDM elastic bandwidth allocation, when compared to a traditional WDM network.

https://www.ceid.upatras.gr/webpages/faculty/manos/kchristodou/journals/ofdm_jlt_revision_2.pdf

Elastic Bandwidth Allocation in Flexible OFDM-Based Optical Networks

Orthogonal Frequency Division Multiplexing (OFDM) has recently been proposed as a modulation technique for optical networks, because of its good spectral efficiency, flexibility, and tolerance to impairments. We consider the planning problem of an OFDM optical network, where connections are provisioned for their requested rate by elastically allocating spectrum using a variable number of OFDM subcarriers and choosing an appropriate modulation level taking into account the transmission distance. Using algorithms developed in our previous works, we evaluate the spectrum utilization gains that can be obtained by utilizing the elastic bandwidth allocation of OFDM, when compared to a traditional WDM network.

https://www.cba.upc.edu/downloads/category/11-articles?download=355:[ARTICLE]A_survey_on_physical_layer_impairments_aware_routing_and_wavelength_assignment_algorithms_in_optical_networks.pdf

A survey on physical layer impairments aware routing and wavelength assignment algorithms in optical networks

Modern optical networking techniques have the potential to greatly extend the applicability of quantum communications by moving beyond simple point-to-point optical links and by leveraging existing fibre infrastructures. We experimentally demonstrate many of the fundamental capabilities that are required. These include optical-layer multiplexing, switching and routing of quantum signals; quantum key distribution (QKD) in a dynamically reconfigured optical network; and coexistence of quantum signals with strong conventional telecom traffic on the same fibre. We successfully operate QKD at 1310 nm over a fibre shared with four optically amplified data channels near 1550 nm. We identify the dominant impairment as spontaneous anti-Stokes Raman scattering of the strong signals, quantify its impact, and measure and model its propagation through fibre. We describe a quantum networking architecture which can provide the flexibility and scalability likely to be critical for supporting widespread deployment of quantum applications.

https://iopscience.iop.org/article/10.1088/1367-2630/11/10/105001/pdf

Optical networking for quantum key distribution and quantum communications

Over the past 25 years, networks have evolved from being relatively static with fairly homogeneous traffic to being more configurable and carrying a heterogeneous array of services. As the applications are ultimately the driver of network evolution, the paper begins with a brief history of circuit, packet, and wave services, along with the development of the corresponding transport layers. The discussion then moves to the evolution of network-node architecture, with an emphasis on the optical-electrical-optical and optical-bypass paradigms. Scalability and cost-effectiveness in meeting network demands are two key factors in the discussion. The evolution of networking equipment, along with the development of the optical control plane, has facilitated a configurable optical layer. The enabling technologies, along with their ramifications, are discussed. Finally, the paper speculates on how capacity might evolve in the future, to handle the undoubtedly new services that are on the horizon.

http://www.monarchna.com/OpticalNetworking25Years-JLT-AnnivIssue-w.pdf

J. Berthold

Papers

Optical Networking: Past, Present, and Future