Optical WDM transmission system with Raman amplifiers comprising optical supervisory channel and controlling system

An optical wavelength division multiplex transmission system (1) for transmitting optical signals (S) on a plurality of wavelength channels has a transmitting terminal (2) and a receiving terminal (3) interconnected by a transmission line (5) with at least one, preferably a plurality of optical amplifiers (4). Each of the optical amplifiers (4) comprises a Raman amplifier (6) with at least one pump light source (8.1-8.3) for pumping the transmission line (5) upstream the optical amplifier (4). It is proposed that each optical amplifier (4) comprises a single tap coupler (11) arranged downstream of the Raman amplifier (6). Optical receiving and transmitting means (14, 15) may be connected to the transmission line (5) via the tap coupler (11) for communication of data (TX, Di) between at least the transmitting terminal (2) and the optical amplifiers (4) on an optical supervisory channel (OSC) with a given wavelength. Alternatively or in addition, monitoring means (12) for monitoring at least one optical transmission parameter may be connected to the transmission line via the tap coupler (11). It is also possible to couple each optical amplifier (4) by means of its tap coupler (11) to a corresponding optical amplifier (4') of a second substantially identical transmission system (1') for transmitting optical signals (S') in an opposite direction via a transmission line (5') of the second system (1'). The all-Raman optical transmission system thus obtained shows improved performance, in particular with respect to loss, noise, PMD, and PDL, while distinguishing itself from prior art systems by its simplicity and corresponding cost-effectiveness.