A supercontinuum light emitting device comprises an effectively CW light source producing light of wavelength .lamda..sub.1 within a specified bandwidth and a nonlinear fiber optically coupled to the light source. The nonlinear fiber has a plurality of fiber segments with different zero dispersion wavelengths .lamda.o.sub.i, where each successive fiber segment has zero dispersion wavelength .lamda.o.sub.i which is larger than the zero dispersion wavelength of the preceding fiber and the zero dispersion wavelength of the first fiber segment is within .+-.20 nm of .lamda..sub.1.