Demultiplexer for light signals with different wavelengths - has photodetectors on upper and lower side of transparent support plate, which selectively absorb desired wavelength

摘要

The device comprises two photodetectors (5,6) e.g. photodiodes, each absorbing selectively one of the two wavelengths. Two photodetectors (5,6) are superimposed and fixed, e.g. glued, on the top face (7) and bottom face (8) of a plate (9) which forms a support and which is transparent to the light, e.g. glass. The outer face (11,12) only of each photodiode (5,6) is covered by a metallisation, in the form of a ring. The second metallisation of each photodiode is a thin layer (14) on each face (7,8) of the support (9), using an electrically conductive transparent material, e.g. tin oxide. The two photodiodes (5,6) give on their terminals (15,16) an electrical signal whose amplitude is proportional to the optical power of each wavelength. To demultiplex, more wavelengths one can add other photodiodes.