An optical communication system using coded multipulse position modulation is described. The position of the pulses in each signalling interval are derived from general binary constant weight codes. The combined coding and modulation of multiple pulses provides a minimum distance between any two signaling frames. Photon counting is used at the receiving end for noiseless optical channel in which only quantum noise exists. For noisy optical channel with avalanche photodetector, threshold demodulation is used in which an optical pulse is considered present in a slot where the photoelectron count exceeds a given threshold. It is shown that this multipulse system gives better performance than the conventional single pulse system. The performance analysis can be applied to and binary constant weight code since only the general parameters of length, minimum distance, and weight of the code are needed.>