Abstract: A method of adjusting Raman gain in an optical amplifier assembly (1a). The method comprises inputting a plurality (N) of optical signals (OS) on different wavelength channels to a backward-pumped Raman active medium (4a) pumped by means of a Raman pump source (5). The proposed method is characterized in that a slope with respect to time in a quantity representative of a respective amplified optical signal (OS?) on at least one existing/surviving channel is determined in case of channel add/drop, and in that the Raman pump source (5) is tuned depending on said change. In this way, fast and reliable Raman pump tuning can be achieved even in an optical amplifier assembly (1a) and an optical transmission system, respectively, which suffer from channel adds/drops.

Abstract: An optical signal amplifier comprises a Semiconductor Optical Amplifier SOA used as semiconductor Amplified Spontaneous Emission ASE source. This SOA produces optical pumping seed which has to be amplified to get a large pump power. With such large pump power, it will be possible to counteract the loss in a fiber link of optical signals transmitted through it by applying said amplified pumping seed as Raman amplification on the optical signals. The invention further relates to a method for amplifying an optical signal comprising the combination of a semiconductor ASE source together with a high-power pump source. Latter will be used to amplify optical pumping seed to be produced by the semi-conductor ASE source. Accordingly, the obtained amplified pumping seed will be used to act as a Raman amplification of optical signals.

Abstract: A two-stage Raman amplifier provides a gain control compensating for span loss variations and changing channel loading. A first amplifier stage (S1) has a first amplifying medium (F1) and a first pump light source (P1, P2, Pn), which is controlled and adjusted by a control unit (CU) to compensate for span loss variations. A second amplifier stage (S2) has a second amplifying medium (F2) and a second pump light source (P?1, P?2, P?n), which is controlled and adjusted by the control unit (CU) to balance changing channel loading.

Abstract: An optical signal amplifier comprises a Semiconductor Optical Amplifier SOA used as semiconductor Amplified Spontaneous Emission ASE source. This SOA produces optical pumping seed which has to be amplified to get a large pump power. With such large pump power, it will be possible to counteract the loss in a fiber link of optical signals transmitted through it by applying said amplified pumping seed as Raman amplification on the optical signals. The invention further relates to a method for amplifying an optical signal comprising the combination of a semiconductor ASE source together with a high-power pump source. Latter will be used to amplify optical pumping seed to be produced by the semi-conductor ASE source. Accordingly, the obtained amplified pumping seed will be used to act as a Raman amplification of optical signals.