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With the increased quantity of Internet traffic, improving spectrum utilization has become a hot topic in the field of optical communication. However, the traditional wavelength-division-multiplexing (WDM) optical networks assign a constant spectral bandwidth (e.g. 50-GHz) to heterogeneous services and thus have limited flexibility and efficiency in spectrum utilization during service accommodation. In order to improve the efficiency in accommodating diverse services with heterogeneous bandwidth requirements, elastic optical networks (EONs) have been proposed. In these networks, spectrum resources can be allocated to different services flexibly according to their respective bandwidth requirements, so that the flexibility and efficiency of spectrum utilization can be remarkably improved. But the spectrum continuity and contiguity constraints in spectrum allocation may induce some isolated, non-aligned and small-sized spectrum segments, which are known as spectrum fragments. With the accumulation of spectrum fragments, the available spectral resources can be exhausted and the networking performance can be affected. Thus, spectrum fragmentation has become an important issue in EONs, and many algorithms have been proposed to reduce the number of spectrum fragments. Among these proposed algorithms, most of them were focus on the defragmentation along normal working paths for services, which might induce traffic disruption for existing service connections and had limited survivability for transmission failure. In order to alleviate the traffic interruption in spectrum defragmentation and improve the survivability for any link failure in transmission, we propose a spectrum defragmentation algorithm based on path-switching mechanism for 1+1 protection in EONs in this paper. Different from previous protection-path-based defragmentation algorithms, the proposed algorithm employs path-switching mechanism to realize active switching between the working path and the protection path according to the usage of the spectrum in the network, so that the two paths can be regarded as their mutual backup paths in the spectrum defragmentation along each of them. In this way, the protection path cannot only provide the survivability for the working path, but also alleviate the traffic disruption during the defragmentation along the working path, while the working path can alleviate the traffic disruption during the defragmentation along the protection path. Simulation results show that the proposed algorithm can realize low blocking probability with reduced traffic disruption for 1+1 protection in EONs.
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