Abstract: An optical coupling assembly is disclosed which comprises a semiconductor laser amplifier to which an optical control signal and an input signal are fed. The semiconductor laser amplifier is responsive to changes in amplitude of the control signal to produce corresponding phase shifts in the input signal. First and second optical couplers are positioned upstream and downstream of the laser amplifier so that a proportion of the input signal and control signal are fed along an optical fiber directly from the first optical coupler to the second coupler. The remaining portions of the input signal and control signal are fed to the laser amplifier where the input signal is phase shifted and then fed to the second coupler. The arrangement is such that the proportion of the input signal output from each output port of the second coupler is selectable by controlling the amplitude of the control signal.