The classical cross-correlator detector is extended to a fuzzy detector used in a digital bandpass M-ary communication system. The fuzzy detector uses the combined fuzzy product to aggregate two fuzzy sets to detect the presence of one signal, buried in a noisy received waveform, out of M possible signals. The error performance of the fuzzy detector is demonstrated via simulation and is compared to the crosscorrelator using M-ary phase shift keying modulation. The error performance of the fuzzy detector is shown to be better than that of the classical correlator detector, in particular, when the noise level is high. The prospect of using the fuzzy detector in an optical communication system is also demonstrated.