All-optical signal gating in cascaded long-period fiber gratings

Abstract

An all-optical signal gating has been demonstrated in cascaded long-period fiber gratings using cross-phase modulation by means of Q-switched pump wave packets. The obtained cascaded twin long-period fiber gratings showed an extremely narrow band of rejection of 0.5-nm bandwidth. Using this narrowband rejection filter, all-optical switching efficiency in long-period fiber grating devices could be enhanced so that they can be operated with relatively low pump intensities. Approximately a 20% modulation depth of a signal wave at 1565 nm was obtained with a pump intensity of 1 GW/cm/sup 2/ at 1064 nm. The experimental results are in good agreement with numerical expectations by the discretized coupled-mode theory, which was previously proposed for the nonlinear long-period fiber grating analysis.