US Patent 7239768 Photonic integrated circuit

A integrated optical circuit comprises an interferometer having a first optical path and a second optical path configured for regenerating an input signal entering the first path by interference at a first coupler between continuous wave (CW) signals from the two optical paths, and a third optical path configured such that a canceling signal passing therethrough cancels, at a second coupler, a traveling signal from the first arm. When the device is operated in a counter-propagative mode, the traveling signal is the CW signal from the first arm. When the device is operated in a co-propagative mode, the traveling signal is the input signal from the first arm.