Abstract: The device includes a first optical circulator connected in series with the line (1e, 1u) in order to receive a signal stream including a carrier to be extracted, modulated by an information signal, and to transmit a signal stream including the same carrier, re-inserted into the stream after having being modulated with another information signal, and a second optical circulator connected to local information processing means, to which it supplies the extracted carrier and from which it receives the carrier to be re-inserted. Between the two circulators there is an optical-fibre bandpass filter that can be tuned to the carrier wavelength.