All-Optical Switching

An optical switch with fully transparent features in both time and wavelength domains is a key device for providing several functions required in optical signal processing. A practical optical switch should have a broad bandwidth over the entire transmission band and should be capable of ultrahigh-speed operation at a data rate of 100 Gb/s or higher. Nonlinear switching without the deformation effect can be achieved by using optical solitons, since they have a uniform nonlinear phase across the entire pulse. Any low-energy dispersive radiation accompanying a train of optical solitons is reflected back, while they are transmitted by the loop. The main limitation of a Sagnac interferometer used to provide cross-phase modulation-induced switching and demultiplexing stems from the weak fiber nonlinearity. Fibers with a length of several kilometers are necessary for a control pulse power in the mW range. Multiple channels can be simultaneously demultiplexed by using multiple control pulses at different wavelengths.