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Spectrally Efficient Optical Systems and Congestion Aware Routing

Most downloaded journal papers in Photonics Technology Letters

2 journal papers by EEE academics in IEEE Photonics Technology Letters have been rated the most popular articles in February and April 2014. Firstly, in February a journal paper on spectrally efficient optical systems from Professor Izzat Darwazeh's Communication and Information Systems Group was the most downloaded paper according to usage statistics. The paper proposes and demonstrates a new optical spectrally efficient frequency division multiplexing (O-SEFDM) system, where non-orthogonal and overlapping sub-carriers are employed to provide higher spectral efficiency relative to optical-orthogonal frequency division multiplexing (O-OFDM). The O-SEFDM technique can increase spectral efficiency in both the electrical and optical domains. It is experimentally shown that for bandwidth saving up to 25%, we can achieve the same performance as O-OFDM. This is the first experimental verification of 25% optical faster than the Nyquist rate. Furthermore, for approximately the same spectral efficiency, 4QAM O-SEFDM outperforms standard 8QAM by 1.6 dB. It is experimentally shown that a lower-order modulation format can achieve a better performance by replacing a higher one.

To read or download the paper which has now been in the top 25 most popular papers for the last 4 months, visit:

Secondly, in April, Dr Seb Savory’s paper titled ‘Congestion Aware Routing in Nonlinear Elastic Optical Networks’ became the most downloaded paper. His paper proposes to use congestion aware routing in a nonlinear elastic optical network and demonstrate its efficacy for the NSFNET reference network (14 nodes, 22 links). The network is sequentially loaded with 100 GbE demands until a demand becomes blocked, this procedure being repeated 10000 times to estimate the network blocking probability (NBP). Three routing algorithms are considered: 1) shortest path routing; 2) simple congestion aware algorithm; and 3) weighted congestion aware routing algorithm with 50, 25, 12.5, and 6.25 GHz resolution flexgrids. For NBP = 1% using a 50 GHz grid, congestion aware routing doubles the network capacity compared with the shortest path routing. When congestion aware routing is combined with a 6.25 GHz resolution flexgrid, a fivefold increase in network capacity is afforded.