Numerically analyzed spectral and temporal management of all-optical switching based on chalcogenide bistable fiber Bragg gratings

All-optical switching in nonlinear chalcogenide fiber Bragg gratings (FBG) can be achieved thanks to the third-order nonlinear optical parameters of chalcogenide glasses. Spectral and temporal characteristics of these gratings are shown. Two principal nonlinear effects with similar power requirements can result in the bistable transmission/reflection of an input optical pulse. In the self-phase modulation (SPM) regime switching is achieved by the intense probe pulse itself. Using cross-phase modulation (XPM) a strong pump alters the FBG refractive index experienced by a weak probe pulse. As a result of this the detuning of the probe pulse from the center of the photonic band gap occurs. This paper is devoted to the comparison of SPM and XPM switching simulated using the time-domain transfer matrix method. Further we present the results of numerical investigation of the effect of modulation instability formed in nonlinear FBGs. The modulation instability occurs if the grating response time is lower than the transit time of the pulse through the grating. Possibilities of the successful elimination of the output pulse degradation via the modulation instability under different conditions implemented into numerical experiments are discussed.