Pulse train amplitude modulation due to continuum resonances in GHz soliton fiber lasers

It is well known that in lasers operating in the soliton modelocking regime, the unavoidable periodic perturbation of the average soliton pulse generates a co-propagating dispersive wave. It was shown by Kelly [1] that at certain wavelengths the accumulated phase difference between the dispersive wave and the soliton over a cavity round trip is a integer multiple of 2π, which leads to constructive interference at those wavelengths, resulting in spectral side-bands. Here we show that constructive interference between soliton and dispersive wave can also occur at a different rate than the cavity round-trip time. Those interferences can be observed as spectral side-bands in the RF spectrum of the detected pulse-train and can be used to estimate the net cavity dispersion. After a propagation distance z the accumulated phase of the circulating soliton φ_sol and dispersive wave φ_disp is: equation.