A single tunable filter WDM Bragg cell is employed to both wavelength demultiplex and detect incoming light beams by the application of a DC tuning signal for wavelength selection, together with an AC component for facilitating detection of data impressed upon selected incoming demultiplexed beams, all in the optical domain, in contrast with the electrical domain, to enhance processing speed. The AC component can perform hetrodyne detection for TV and telephone analog communication systems, or can detect digital signals for DSL internet communication systems, and cost savings result from the use of a single compact cell tuned by the composite signal permitting demultiplexing and detecting in one cell component. The resulting versatility enables use of the single cell in WDM and TDM, WDM and spread spectrum, and WDM packet switching and TCP/IP header digital address recognition systems.