ABSTRACTThis paper reports on light filtering devices based on a-SiC:H tandem pi´n/pin heterostructures. The spectral sensitivity is analyzed. Steady state optical bias with different wavelengths, are applied from each front and back sides and the photocurrent is measured. Results show that it is possible to control the sensitivity of the device and to tune a specific wavelength range by combining radiations with complementary light penetration depths. The transfer characteristics effects due to changes in the front and back optical bias wavelength are discussed.Input red, green and blue pulsed communication channels are transmitted together, each one in a specific bit sequence and the multiplex signal is analyzed. By superimposing appropriate background and depending on the channel/background wavelength combinations, the device behaves as a long- or a short- pass filter, producing signal attenuation, or as an amplifier, producing signal gain. A physical model is presented to support the filter properties of the device.