Experimental observation of a new modulational instability spectral window induced by fourth-order dispersion in a normally dispersive single-mode optical fiber

We experimentally investigate the influence of the fourth-order dispersion (FOD) on the onset of scalar spontaneous modulational instability (MI) in a single-mode optical fiber. This study was performed in the normal dispersion regime of a dispersion-shifted fiber pumped by a quasi-continuous laser diode operating near the zero-dispersion wavelength. We experimentally demonstrate the evidence of a new MI spectral window due to the FOD effect in the normal dispersion regime. The effect of random fluctuations of the zero-dispersion wavelength along the fiber is considered for effective gain prediction. The measured modulation frequencies, which range from 5 up to 9 THz for an input power of 7 W, are in very good agreement with those obtained from the linear stability analysis. The FOD induced-MI can be used for broadband wavelength conversion. In addition it can be of a great interest for the generation of ultra-high repetition rate train of femtosecond pulses. (C) 2003 Elsevier B.V. All rights reserved.