Introduction

Studies of supercontinuum generation in photonic crystal fibers or dispersion-shifted highly nonlinear fibers have led to renewed interest in SC generation in other fiber types. For example, it was shown that fibers with a steadily-decreasing diameter in which the dispersive and nonlinear characteristics change as a function of propagation distance can lead to significant enhancement of the SC bandwidth and allow for an additional degree of control of the SC spectrum. In fact, it was the use of fibers with dispersion-varying profiles that motivated in the mid-1990s the pioneering work on SC generation intended for telecommunication applications [see e.g. Morioka et al., 1994a, 1994b, 1995, 1996; Mori et al., 1995]. Of course, it was already well known that efficient adiabatic pulse compression could be achieved in dispersion-varying fibers (Dianov et al., 1986), but these mid-1990s studies, anterior to the development of PCFs, were the first to specifically suggest that fibers with longitudinally-varying dispersion could be advantageous in generating broad and/or flat SC spectra (Lou et al., 1997; Mori et al., 1997). With the development of the theoretical understanding of SC generation process (see other chapters) renewed interest in dispersion-engineering has therefore occurred naturally. In this context, a key result that was reported is the demonstration of coherent SC generation in millimeter lengths of tapered fibers where the diameter of the fiber is controlled as a function of length to a great degree of accuracy (Lu and Knox, 2004).