ABSTRACT
The photonic crystal fiber, a new paradigm in fiber optics, was devised by P. St. J. Russell almost twenty years ago. The propagation of light beams in air for kilometers, the emission of multi-kilowatt continuous wave radiation in a single transverse mode, the generation of octave-spanning light continuum or frequency combs are some breakthroughs brought by researchers in the field of photonic crystal fibers (PCF). The power of the photonic crystal fiber concept resides in its versatility in terms of morphology, application and material used. As a consequence, this phrase includes so many kinds of optical fibers that this chapter cannot give an exhaustive overview. It is possible, however, to derive two generic classes of PCFs according to the mechanism on which propagation relies.
