Abstract: In a high speed optical clock extraction arrangement, an incoming digital signal is divided between two paths (11, 25). The signal on one path (25) is fed direct to a receiver (203), while the signal on the other path (11) is fed to a non-linear optical amplifier (1) which has separate gain and absorbing regions. The non-linear optical amplifier (1) is triggered by the incoming signal to pulsate at a clock frequency contained in the signal, and the resultant strong output clock signal is coupled into the path (25) carrying the incoming signal to the receiver (203). The non-linear optical amplifier (1) can provide a very high frequency clock output as a result of selective modification of the carrier lifetime.