Measurement of the nonlinear parametric instability gain in dispersion oscillating fibers.

We report the observation of the parametric gain band distortion in the nonlinear (depleted) regime of modulation instability in dispersion oscillating fibers. We show that the maximum gain is shifted even outside the boundaries of the linear parametric gain band. Experimental observations are confirmed by numerical simulations.

Experimental investigation of short pulse Raman amplification with backward pumping.

We report an experimental study on the backward-pumped Raman amplification of short pulses into a 20.3 km long optical fiber. We demonstrate that the gain and the pump saturation depend on the pulse duration. We also reveal that for short enough pulses, the amplification process remains linear, and very high peak powers, even larger than the Raman pump, are achievable. Numerical simulations reproduce the experimental results with excellent agreement.

"Extraordinary" modulation instability in optics and hydrodynamics.

The classical theory of modulation instability (MI) attributed to Bespalov-Talanov in optics and Benjamin-Feir for water waves is just a linear approximation of nonlinear effects and has limitations that have been corrected using the exact weakly nonlinear theory of wave propagation. We report results of experiments in both optics and hydrodynamics, which are in excellent agreement with nonlinear theory. These observations clearly demonstrate that MI has a wider band of unstable frequencies than predicted by the linear stability analysis. The range of areas where the nonlinear theory of MI can be applied is actually much larger than considered here.

Observation of doubly periodic solutions of the nonlinear Schrödinger equation in optical fibers.

We report the first, to the best of our knowledge, experimental observation of doubly periodic first-order solutions of the nonlinear Schrödinger equation in optical fibers. We confirm, experimentally, the existence of A-type and B-type solutions. This is done by using the initial conditions that consist of a strong pump and two weak sidebands. The evolution of power and phase of the main spectral components is recorded using heterodyne time-domain reflectometry. Another important part of our experiment is active loss compensation. We reach a good agreement between theory and experiment.

Observation of four Fermi-Pasta-Ulam-Tsingou recurrences in an ultra-low-loss optical fiber.

We report the experimental observation of more than four Fermi-Pasta-Ulam-Tsingou recurrences in an optical fiber thanks to an ultra-low loss optical fiber and to an active loss compensation system. We observe both regular (in-phase) and symmetry-broken (phase-shifted) recurrences, triggered by the input phase. Experimental results are confirmed by numerical simulations.