Optical receiver

A network head-end station arranged to receive an upstream TDMA frame comprising interleaved optical signals from a plurality of terminations connected to the head-end station by a fibre network, the station including an opto-electronic receiver and a DC clamping circuit for the opto-electronic receiver, characterised in that:

• the terminations are arranged such that none of the terminations transmit in a quiet phase of the upstream TDMA frame;
• the DC clamping circuit is arranged, when operated, to clamp signals received during the remainder of the TDMA frame to a DC reference level received during the quiet phase;
• and the station further including a clamping pulse generator arranged to generate a pulse at a predetermined time falling within the quiet phase to operate the DC clamping circuit.