Experimental Observation of the Fundamental Dark Soliton in Optical Fibers

We present evidence of soliton propagation by 185-fsec dark pulses at a wavelength of 0. 62 in a 1. 4-m length of single-mode optical fiber. Our experiments utilize specially shaped, antisymmetric input pulses, which closely correspond to the form of the fundamental dark soliton. At appropriate power levels the dark pulses propagate without broadening. Our measurements are in quantitative agreement with numerical solutions to the nonlinear Schr\"odinger equation and constitute the first clear observation of the fundamental dark soliton in optical fibers.