Wavelength Division Multiplexing (WDM) technology expands fiber capacity by transmitting multiple signals at different wavelengths. Read on to learn the fundamentals of this useful technology. This technique enables bidirectional communications over a. Corning coarse wavelength division multiplexing (CWDM) solutions utilize advanced thin-film-filter technology. CWDM solutions are available in industry-standard 20 nm spacing with options for a 1310 nm RF overlay bypass as well as single or bidirectional test ports.