Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) based Elastic Optical Network (EON) is one of the emerging technologies being considered for next generation high data rate optical network systems. Routing and Spectrum Allocation (RSA) is an important aspect of EON. Apart from spectral fragmentation created due to spectrum continuity and contiguity constraints of RSA, transmission impairments such as shot noise, amplified spontaneous emission (ASE) beat noise due to coherent detection, crosstalk in cross-connect (XC), nonlinear interference, and filter narrowing, limit the transmission reach of optical signals in EON. This paper focuses on the cross-layer joint optimization of delay-bandwidth product, fragmentation and link congestion for RSA in CO-OFDM EON while considering the effect of physical layer impairments. First, we formulate an optimal Integer Linear Programming (ILP) that achieves load-balancing in presence of transmission impairments and minimizes delay-bandwidth product along with fragmentation. We next propose a heuristic algorithm for large networks with two different demand ordering techniques. We show the benefits of our algorithm compared to the existing loadbalancing algorithm.
This work proposes a physical layer impairment-aware routing, modulation, spectrum, and core allocation optimization framework in elastic optical networks with multi-core fibers. The inter- and intra-core impairments considered are crosstalk between adjacent cores, in-band crosstalk, non-linear interference, and amplified spontaneous emission noise. Further, bit loading is used in the proposed framework, independently modulating each demand’s frequency slots, depending on each frequency slot’s interference level. An optimization framework is initially developed for benchmarking purposes, followed by a heuristic algorithm and demand ordering technique for larger-sized networks. For both optimization and heuristic approaches, an end-to-end acceptable bit error rate is ensured for each provisioned demand. The benefits of the proposed approach are illustrated through simulations, demonstrating that they achieve lower fragmentation and less spectrum usage as compared to other state-of-the-art techniques.
We focus on quality of transmission (QoT) guaranteed routing, modulation, and spectrum allocation (RMSA) in shared backup path protection (SBPP) based elastic optical networks (EONs) in the presence of nonlinear impairments. Allocating a suitable modulation format (MF) to ensure end-to-end QoT (E2E QoT) in a survivable EON offers critical challenges because each single link failure results in the failure of different network connections. As a consequence, different working and backup path allocations exist in the network for different failures, which lead to different nonlinear interference (NLI) power on any frequency slots (FSs). This demands a robust RMSA design to decide the suitable MF for each FS to ensure the E2E QoT under two scenarios: any single link failure and no failure. For this purpose, we propose a robust SBPP-NLI aware (SBPP-NLIA) algorithm to ensure E2E QoT with a multi-objective function that enables the joint sharing of backup FSs as well as transceivers and minimizes the overall network fragmentation. In the process, we introduce robust bitloading in our SBPP-NLIA to allocate different MFs for different FSs where we also perform optimal MF allocation for each FS of every connection. Next, we ensure the QoT of existing connections while establishing each new connection without reserving any margin. To achieve this with less complexity, we propose a recursive method to calculate the NLI for existing connections. Simulation results demonstrate that our proposed SBPP-NLIA performs 10.01% and 14.19% better in terms of, respectively, the bandwidth blocking probability and fragmentation compared to a full-load assumption scheme with an 85 Tb/s traffic load.
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