Broad bandwidths from frequency-shifting solitons in fibers

By pumping a fiber in the anomalous group-velocity-dispersion regime with a color-center laser we generate pulses with tau greater, similar 100 fsec covering a wide spectral range of 1.55 microm < lambda < 1.85 microm. Cross-correlation measurements show the lack of correlation between different parts of the spectrum. Computer simulations show that modulation instability and the soliton self-frequency-shift effect initiate a multisoliton collision process that results in narrow, high-intensity, fundamental solitons. The observed broad spectra correspond to an ensemble average over these solitons, which start from noise and frequency shift by different amounts.