ABSTRACT
The nonlinear effects generated in the fibers severely affect the performance of optical communications systems, since they impose limits on the launched power of the signals, channel bit rate, channel spacing, transmission bandwidth, hence the entire information capacity of such systems. The fiber nonlinearity can be further enhanced by appropriately tailoring its structure. Microstructured optical fibers (MOFs) represent a new class of optical fibers that are characterized by the fact that the silica cladding presents array of embedded air holes. In a solid-core MOF, increasing the hole-pitch ratio reduces the effective mode area, due to the increased contrast between the refractive index of the core, the average refractive index of the cladding. The physics of parametric amplification in highly nonlinear fibers (HNLFs) is similar to that of standard optical fibers. Four-wave mixing in HNLFs can be used also to stabilize the output of multiwavelength erbium-doped fiber lasers, through the continuous annihilation and creation of photons at the wavelengths of interest.
