A noise discriminator circuit and a noise discrimination method in a burst mode receiver is configured to determine the validity of an incoming burst signal by analyzing the timing of the signal edges of incoming signal to look for a time duration conforming to the preamble data bits of a valid burst signal. In one embodiment, the noise discriminator circuit and method analyze the time duration between signal edges of the same pulse of an incoming signal. In another embodiment, the noise discriminator circuit and method analyze the time duration between a first set of pulses of an incoming signal and the time duration between signal edges of a second set of pulses of the incoming signal. When the time durations are within a given time range relating to a predetermined timing separation of a valid burst signal, the incoming signal is validated as a valid burst signal.