Compensating fiber gratings for source flatness to reduce multiple-access interferences in optical CDMA network coder/decoders

A fiber-Bragg-grating (FBG)-based optical code-division multiple-access (OCDMA) network coder/decoder (codec) is investigated for its interference suppression induced by nonflattened broad-band lightwave sources. Since each network user with different signature address code has different spectral distribution, the nonflattened light sources will cause multiple-access interference (MAI). Flatness compensation schemes are proposed to solve the MAI effects induced by nonflattened broad-band light sources. By arranging the same coding scheme but in different spectral coding band, spectral chips from FBG coder/compensator will incoherently power summed in the photodetectors to approach a more flattened power level. Signal-to-interference ratio (SIR) performances are evaluated with such compensation method for the discussed OCDMA network.