Abstract: An optical transmission system having a supervisory system of devices disposed along an optical link. Counter-propagating Raman amplifiers are disposed along the optical link. Low-frequency supervisory signals are superimposed on the optical signals traveling on the optical link by suitable modulators in the devices disposed along the line. Counter-propagating Raman amplifiers amplify optical signals and do not introduce a substantial amount of attenuation on the low-frequency supervisory signals.

Abstract: An optical transmission system having a supervisory system of devices disposed along an optical link. Co-propagating Raman amplifiers are disposed along the optical link. Low frequency supervisory signals are superimposed on the optical signals traveling on the optical link by suitable modulators in the devices disposed along the line or by the same co-propagating Raman amplifiers. Regeneration of the supervisory signal is provided in at least one device disposed along the optical link in order to counteract attenuation introduced on the supervisory signal by the co-propagating Raman amplifiers.

Abstract: An optical transmission system having a supervisory system of devices disposed along an optical link. Co-propagating Raman amplifiers are disposed along the optical link. Low frequency supervisory signals are superimposed on the optical signals traveling on the optical link by suitable modulators in the devices disposed along the line or by the same co-propagating Raman amplifiers. Regeneration of the supervisory signal is provided in at least one device disposed along the optical link in order to counteract attenuation introduced on the supervisory signal by the co-propagating Raman amplifiers.

Abstract: An optical transmission system having a supervisory system of devices disposed along an optical link. Counter-propagating Raman amplifiers are disposed along the optical link. Low-frequency supervisory signals are superimposed on the optical signals traveling on the optical link by suitable modulators in the devices disposed along the line. Counter-propagating Raman amplifiers amplify optical signals and do not introduce a substantial amount of attenuation on the low-frequency supervisory signals.

Abstract: An optical communication line having a first control unit; an optical transmission fibre connected to the first control unit for transmitting an optical signal; and an optical amplification unit inserted along the optical transmission fibre for amplifying the optical signal. The optical amplification unit has an optical amplifier for amplifying the optical signal, a magneto-optical attenuator connected to the optical amplifier, and a control device for regulating the light transmissivity of the magneto-optical attenuator, wherein the first control unit has a magneto-optical attenuator and a control device for regulating the light transmissivity of the magneto-optical attenuator so as to superimpose service informations on the optical signal. In the optical amplification unit, the control device is suitable to regulate the light transmissivity of the magneto-optical attenuator so as to superimpose service informations on the optical signal.