Optically controlled optical switch

An optical switch comprising an interferometer having:

• an input port and an output port;
• a source of optical signals at a first wavelength coupled to the input port;
• an optical coupling means for splitting an input optical signal into two signal portions and
• for combining the two signal portions at the output port to provide an output signal having an intensity dependant on the phase difference between the two portions when they combine;
• a source of control optical signals coupled to the interferometer such that the phase difference between the signal portions at the output port is dependant on the intensity of the control optical signals;
• characterised in that means are provided for combining at least two optical pulse streams to constitute the source of optical control signals, the pulses of distinct optical pulse streams being non-interferometric.

An AND gate comprising:

• an optical fiber loop interferometer;
• an optical coupler for receiving and splitting an optical input signal into two signal portions, counterpropagating the two signal portions around the fiber loop, combining the two signal portions having propagated around the fiber loop and providing at an output port an optical output signal having an intensity dependent on the phase difference between the two signal portions when combined;
• means for providing an optical input signal at the input port of said optical coupler;
• means for providing a first optical pulse stream;
• means for providing a second optical pulse stream;
• the pulses of said first and second pulse streams being non-interferometric;
• means for combining said first and second pulse streams and applying them to the input port of said optical coupler;
• and
• whereby when both said first optical pulse stream and said second optical pulse stream are present the output signal at said optical output port will be fully switched.