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Traditional dense wavelength division multiplexing (DWDM) technology is no longer enough to meet the extensive growth in the demand of bandwidth in an efficient and effective manner under the fixed grid environment. Thus, a technology is needed to overcome the challenges raised by the ever-increasing demand of bandwidth in an effective manner with efficient utilization of spectral resources. To solve this problem, an elastic optical network (EON) paradigm comes into existence. It uses a flexible grid technology that removes the limitations of fixed grid DWDM technology and increases the channel capacity to meet current bandwidth demand with proper utilization of optical spectrum. We present the evolution of EON from the DWDM network. We have discussed the main components and characteristics of EON that includes superchannel and sliceable bandwidth variable transponder (SBVT). Thereafter, we discuss the different modulation and transmission techniques used in EON. Next, we present the recently proposed architectures of SBVT followed by its applications. Lastly, we have discussed various subcarrier generation techniques in brief. [ABSTRACT FROM AUTHOR]

Elastic Optical Networks (EONs) are extensively accepted promising solution for future ultra-high-speed optical transmission, due to their capability of efficient and flexible assignment of immense optical bandwidth to the heterogeneous traffic demand. However, it undergoes through an aggravated form of the spectrum fragmentation problem due to the heterogeneous bandwidth requirements, spectrum continuity and contiguity constraints. Several techniques have been presented in the literature to get the optimal solution of this problem while multi-path provisioning comes out to be very compelling among them. Although, it creates further challenges due to high hardware requirement and more spectrum consumption due to guard-bands. In this paper, we propose a novel scheme, called optimal spectrum defragmentation (DF) strategy with split spectrum approach (OSDSSA), to tackle this limitation of multi-path provisioning by utilizing minimum number of spectral paths, which improves the scalability, reduces the extra spectrum consumption by guard-bands and avoids the exhaustion of transponders at nodes. The proposed scheme initially serves a connection request using k-shortest routing paths and first-fit spectrum allocation policy in a best possible way. In case, if a connection request cannot be served then the proposed mechanism proceeds with the triggering of Process Defragmentation on the link disjoint shortest paths followed by splitting of traffic demand on corresponding link-disjoint paths. The Process Defragmentation is triggered on the active connections at the immediate right and left of the largest continuous available spectrum block on the link-disjoint shortest paths sequentially until the requested amount of frequency slots (FSs) are achieved. In this work, reconfiguration includes spectrum re-tuning without changing the routing paths, thereby reducing the unnecessary service disruption, DF complexity and cost, leading to improvement in quality of service (QoS) of the network. The performance of the proposed scheme has been assessed through simulation results where single path and multi-path provisioning algorithms have been considered as benchmarks. Through our proposed scheme bandwidth blocking performance, spectrum utilization ratio, and degree of fragmentation have also been improved significantly. [ABSTRACT FROM AUTHOR]