An optical demultiplexor utilizes a single optical interference filter dispo sed between an input end and an output end of the device. The filter is preferably house d within a cavity in a glass block having an upstanding input end, endwall. The optical filter is a wavelength selective means having a wavelength characteristic dependent upon an angle o f incidence. The device has a plurality of reflective surfaces disposed at the input end for reflecting light reflected from the filter, back to the filter at different predetermined ang les. Each different predetermined incident angle allows a different predetermined wavelength of light to pass through the filter to an output end being spatially separated from other pre determined wavelengths that pass through the filter. The reflective surfaces are prefer ably formed in the upstanding endwall of the glass block. Sixteen channels can be separated by thisdemultiplexor.
