Ultrafast, all-optical switches have generated a lot of interest for future optical communication systems and optical processing, particularly in their application in optical demultiplexers for time-division-multiplexed communications.
A group from NEC Corp.'s Optoelectronics and High Frequency Device Research Laboratories in Tsukuba, Japan, has developed a polarization-discriminating symmetric Mach-Zehnder all-optical switch. Incorporating birefringent crystals, a nonlinear waveguide and polarizer into the device, the group demonstrated 200-fs switching and 1.5-Tb/s demultiplexing. Details of the group's work appear in the November 1998 issue of IEEE Photonics Technology Letters.