Tree optical transmission network

An optical transmission network comprising a concentrator (1), a plurality of stations (ST1-ST3), and an optical interconnection tree linking respective sending points (K1-K3, Ki) of the stations to the same receiving point (I) of the concentrator, said interconnection tree including a common optical link (OL) having a first end coupled to said receiving point (I) and a second end (J) coupled to each of said sending points (K1-K3, Ki) of the stations via a coupling system (C) and access links (F1-F3) associated with the respective stations, each access link being a point-to-point link connecting the coupling system (C) to the sending point of a single station and enabling the propagation of optical waves from the station to the coupling system (C) in an “uplink” propagation direction or in an opposite “downlink” propagation direction, said stations including senders adapted to send from their respective sending points (K1-K3, Ki) optical signals (λu1, λu2, λu3) each carried by the same “uplink” wavelength (λu) and propagating in said uplink propagation direction, each station (STi) including a carrier detection system (3) able to detect the presence at the sending point (Ki) of an optical wave at said uplink wavelength (λu) that did not come from the sender of the same station, and said detection system (3) cooperating with sending control means (5) to inactivate said sender if such presence is detected,

• said network being characterized in that it includes:
• an emulator (LDa, Ca, G1-G3) adapted to send auxiliary waves (λa1, λa2, λa3) at said uplink wavelength (λu) and to couple them into said access links (F1-F3) so that they propagate in said downlink propagation direction, and
• a control system (2a) of said emulator for selectively activating the sending of said auxiliary waves.