Limitations imposed by Fabry-Perot sliding filters on soliton WDM transmission

Summary form only given. In a soliton transmission line with Fabry-Perot etalons as sliding-frequency guiding filters, the channel spacing is determined by the separation between the frequencies at the peaks of the filter transmission function. By changing the free spectral range of the filter one may bring the wavelength-division multiplexing (WDM) channels closer. On the other hand, the filter characteristics cannot be changed arbitrarily because at some parameter values the soliton cease to propagate stably. We analyze how closely one can bring WDM channels with Fabry Perot etalons while maintaining stable soliton propagation.