Abstract

Recent experiments have shown that optical fibers have the capability of generating and transmitting information at THz rates.¹ This motivates the demand of future optical communication and computing systems for optical processing devices operating before electronic detection, i.e., in an all-optical fashion. The possibility of controlling the switching of an optical signal by means of another light beam was initially demonstrated with bistable elements, e.g., the nonlinear Fabry-Perot.² In this case, main limitations to the switching speed arise from the resonator transit time and thermal heating. Pipeline all-optical processing of a data stream is also possible in a traveling wave configuration, for example using a nonlinear directional coupler³ or a Mach-Zehnder interferometer.⁴ In this case, interaction between controlling and controlled signals occurs through the intensity dependence of the refractive index, and successive pulses may get switched simultaneously while propagating along the device, so that the traveling time no longer sets a limitation to the switching speed. The shortest pulses which can be processed will then be determined by the response time of the nonlinearity, which can be of the order of a few optical cycles for glass fibers, and the combined effect of group-velocity dispersion (GVD), self-phase modulation (SPM) and cross-phase modulation (CPM).

© 1989 Optical Society of America