Abstract: A clock signal at a divided clock rate is obtained from an optical signal stream at a higher clock rate. The optical signal stream at the higher clock rate is applied to an all-optical non- linear gate. There is feedback from the first output of the gate to its control input. The optical signal at a divided clock rate is present at a second output of the gate. The gate may comprise a non-linear loop mirror. A number of such gates may be cascaded in series to provide an output at a clock rate divided by 2n, where n is an integer.

Abstract: An optical switch includes a semiconductor gain medium and inputs for an optical control signal applied to the semiconductor gain medium. The switch has a pair of arms (31, 32) arranged in a Mach-Zehnder configuration. A semiconductor gain medium (SOA1, SOA2) is connected in each arm. A fixed phase shifting element PE is also connected in one arm. Control signals are applied to each of the semiconductor gain media. There is a delay between the control signals selected so that a desired one of the optical pulses experiences a differential phase shift and so we switch to a different output of the multiplexer. In one example, the semiconductor gain media are provided by discrete semiconductor devices sandwiched between a pair of planar substrate on which waveguides forming the other components of the switch are formed. The switch may be used for demultiplexing OTDM signals.