Abstract-The nonlinear effects in optical fiber occur either due to intensity dependence of refractive index of the medium or due to inelastic-scattering phenomenon. This paper describes various types of nonlinear effects based on first effect such as self-phase modulation, cross-phase modulation and four-wave mixing. Their thresholds, managements and applications are also discussed; and comparative study of these effects is presented.

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Abstract-The group velocity dispersion (GVD) imposes severe limit on information carrying capacity of optical communication systems. By choosing appropriate pulse shape highly stable light pulses known as solitons are generated when effect of GVD is balanced by self-phase modulation (SPM). The application of solitons in communication systems opens the way to ultrahigh-speed information superhighways. Transmission speed of order of Tbit/s can be achieved if optical amplifiers are combined with WDM in soliton based communication systems.

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A series of α, β-(9,10-dihydroanthracene-9,10-diyl)-N-arylsuccinimide derivatives has been prepared and their N.M.R. spectral studies are reported. The effect of the substituents at the N-phenyl group on the conformational process about the aryl C-N bond has been investigated.The asymmetric cage moiety present in this system was employed for the conformational study.� The N.M.R. spectra provided evidence for the non-planar conformation and restricted rotation about the aryl C-N bond in the case of ortho-substituted derivatives. Electronegative substituents were found to have a preferred conformation (anti to the cage moiety). The energy barrier (ΔGt) of the order of 86 kJ/mol has been determined by their temperature-dependent spectra. Free rotation about the aryl C-N bond was observed for the meta- and para-substituted derivatives. No buttressing effect by meta substituents has been noticed.