A method of distance synchronization of a series of remote optical receiver points with an optical transmission point, the method including the steps of: (a) sending an optical timing pulse from the optical transmission point to each of the series of remote optical receiver points and back; (b) determining a round trip time of the timing pulse; and (c) storing an indicative measure of the roundtrip time of the timing pulse and utilising the indicative measure to adjust the timing of signals at the remote optical receiver points to determine the relative reception time of signals received by the series of remote optical receiver points.