Cyclic spectra for wavelength-routed optical networks

We propose occupying the guard bands in closely spaced WDM systems with redundant signal spectral components to increase tolerance to frequency misalignment and channel shaping from multiplexing elements. By cyclically repeating the spectrum of a modulated signal, we show improved tolerance to impairments due to add/drop multiplexing with a commercial wavelength selective switch in systems using 5%-20% guard bands on a 50 GHz DWDM grid.