A device for use in optical signal control is presented. The device comprises an amplification waveguide, including a pumpable medium, and a reference and a control inputs and an output selectively allowing transmission of light respectively into and out of said amplification waveguide. The reference input, the amplification waveguide and the output define together a transmission scheme for reference light through the pumpable medium. The control input and the amplification waveguide define a depletion scheme for the pumpable medium and control light. The device thus allows for controlling an output signal, formed by the transmission of the reference light, by controllable depletion of the pumpable medium.