For the last two decades, varieties of optical fibers have been developed for optical communications in order to cope with ever increasing demand on bandwidth, data rate, and transmission distance. Due to the small index variation over the transverse cross-section, modal characteristics of the conventional fibers cannot be changed significantly to meet certain requirements in terms of dispersion, and field confinement. Recently, Photonic crystal fibers (PCFs), also called holey fibers or microstructure optical fibers, have been under intensive study as they offer possibilities to surmount the above limitation. With the design flexibility by proper choosing of the microstructure parameters, The PCFs can be tailored to produce unique and useful modal characteristics not achievable in conventional solid core fibers, such as single-mode operation at a wide wavelength range, highly tunable dispersion, and highly controllable mode effective areas for linear and nonlinear...
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