Square optical pulse generator

Claim 1

A square optical pulse generator comprising: a first optical coupler (8) having a first and a second pair of optical communication ports (10, 12 and 14, 16) in which substantially equal first signal portions of an optical signal at a first wavelength received at a port (10) of one pair are coupled to the two ports (14,16) of the other pair of ports; an optical waveguide (6) coupling together the second pair of ports having an interaction section which includes a material having a non-linear refractive index; a cw optical source (16) for providing a cw optical signal at the first wavelength optically coupled to a first port (10) of the first pair of ports (10, 12); a pulsed optical source (20) for providing a pulsed optical signal at a second wavelength optically coupled to the interaction section (6) so the pulsed optical signal propagates along it in substantially one direction; the intensity of the pulsed optical signal being sufficient to provide a relative phase shift in the first signal portions as they propagate round the optical waveguide (6) and the interaction section being longer than the inverse of the absolute difference in group delays of the cw and pulsed optical signals.