An optical demultiplexer system for separating adjacent wavelength bands without losing inter-band channels and comprising a first filter stage (210) of relatively narrow passband and relatively high selectivity in order to extract all of the inter-band channels. The first stage is followed by a second filter stage (240) of relatively broad passband and relatively low selectivity to extract the wavelength bands delivered by the first filter stage. Such a system makes it possible to use the inter-band channels, in particular for managing the network and the wavelength bands.