An optical system (100) comprising: a transmitter module (102) configured to transmit a sequence of optical pulses (300), each optical pulse in the sequence (300) having a different magnitude to each other optical pulse in the sequence (300); a receiver module (104) comprising one or more optical signal detectors, the receiver module (104) configured to receive the sequence of optical pulses (300) transmitted by the transmitter module (102); and one or more processors (110) configured to process the sequence of optical pulses received by the receiver module (104) to select an optical pulse from the received sequence of optical pulses (400) based on one or more predetermined criteria. The one or more predetermined criteria include a criterion that the selected optical pulse does not saturate the one or more optical signal detectors.