A method of optical communication includes providing a plurality of optical signals each associated with a distinct channel of a composite optical signal. A unique pilot tone signature is superimposed on each channel. The spectral composition of each signature includes a plurality of frequencies. In one embodiment, binary frequency shift keying at a frequency f.sub.m is used to shift between instantaneous frequencies f.sub.1 and f.sub.2 wherein f.sub.2+.DELTA.f=f.sub.1-.DELTA.f=f.sub.c. Choosing.DELTA..times..times..apprxeq. ##EQU00001## produces a spectrum having a plurality of dominant components at least some of which have substantially the same amplitude. A method of detecting the presence of a selected pilot tone signature having a plurality n of dominant spectral components F.sub.1 . . . F.sub.n includes generating a power spectrum P.sub.0(f). S.sub.k(f) is calculated as a product of a plurality of frequency shifted versions of P.sub.0(f), where k.di-elect cons.{1 . . . n}. The existence of a dominant spectral component at F.sub.k indicates the presence of the selected pilot tone signature.