@article {8495,
	title = {Investigation of Spectrum Granularity for Performance Optimization of Flexible Nyquist-WDM-Based Optical Networks},
	journal = {Journal of Lightwave Technology},
	volume = {33},
	number = {23},
	year = {2015},
	pages = {4767-4774},
	abstract = {The idea behind flexible optical transmission is to optimize the use of fiber capacity by flexibly assigning spectrum and data rate adapted to the needs of end-to-end connection requests. Several techniques have been proposed to this end. One such technique is based on the utilization of Nyquist-shaping filters with the aim of reducing the required channel spacing in flexible single-carrier and super-channel optical transmission systems. Nonetheless, the imperfect shape of the filters used at the bandwidth-variable transceivers and wavelength-selective switches compels the necessity to allocate a certain spectral guard band between (sub-)channels. Bearing this is mind, in this paper, we focus on the evaluation of the network-level performance, in terms of the filter characteristics and the WDM frequency-grid granularity, of flexible Nyquist-WDM-based transmission. We demonstrate that a granularity of 6.25 GHz offers a good compromise between network performance and filter requirements for spectrum assignment to single-carrier and super-channel signals. However, for subchannel allocation within a super-channel, granularities as fine as 3.125 GHz are required to take advantage of filters with resolutions in the region of 1-1.2 GHz. Finer filter resolutions and frequency slot granularities provide negligible performance improvement.},
	url = {http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=7297800},
	author = {Pouria Sayyad Khodashenas and Jos{\'e} Manuel Rivas-Moscoso and Behnam Shariati and Dan M. Marom and Dimitrios Klonidis and Ioannis Tomkos}
}
