Abstract: An optical communication system comprising a plurality of optical signal communication paths, and a plurality of terminals coupled to the plurality of communication paths. A connection request is made by a calling terminal to a called terminal with an optical signal at a control wavelength via the communication path. A wavelength control unit monitors the communication paths and in response to the connection request signal selects an optical signal wavelength to be used by the terminals, out of any unused wavelengths on the communication paths. Further, the wavelength control unit informs the calling and called terminals of the selected wavelength via a wavelength information optical signal at the control wavelength. The calling and called terminals, responsive to the wavelength information signal, set their transmitting and receiving wavelength to the selected unused wavelength.

Abstract: In a composite concentration system of the type utilizing a time division system in which voice signals are digitized and then concentrated in a traffic, there are provided a first subscriber line interface means of a first type which connects subscriber lines directly to subscriber line interface circuits, a second subscriber line interface means of a second type which connects subscriber lines to subscriber line interface circuits via a space division concentration switch and a time division concentration switch connected to the first and second subscriber line interface means via switching interfaces.