Patent ID: 7277221

Claim:
A cascaded Raman amplifier combination that is responsive to an optical signal having a plurality of optical signal channels, comprising: a first Raman fiber amplifier being coupled to a first optical fiber facility and having at least one adjustable optical pump; a second Raman fiber amplifier being coupled to a second optical fiber facility and having at least one fixed optical pump; a measurement unit configured to determine an input signal power variation for at least one wavelength region, the plurality of optical signal channels being associated with the at least one wavelength region; a control unit configured to: determine a fixed pump power value for the at least one fixed optical pump of the second Raman fiber amplifier; and determine a pump power adjustment for the at least one adjustable optical pump of the first Raman fiber amplifier using a predetermined function that depends on the input signal power variation; the first Raman fiber amplifier, coupled to the control unit though a feed-forward configuration, configured to adjust the at least one adjustable optical pump in accordance with the pump power adjustment; the control unit configured to utilize the predetermined function corresponding to a linear relationship between the pump power adjustment and the input signal power variation of the at least one wavelength region; and the second Raman fiber amplifier configured to adjust the at least one fixed optical pump in accordance with the fixed pump power value, the predetermined function comprising: P d ( j ^ , t ) ≈ P d ⁢ ⁢ o ( j ^ , t ) + ∑ k = 1 K ⁢ T ^ dL ( j ^ , k ) [ S L ( k , t - T ^ ) - S L ⁢ ⁢ 0 ⁡ ( k ) ] , wherein k correspons to a k th wavelength reion, t corresponds to a time instant, j corresponds to a j th forward Raman pump, P d (j,t) denotes a required power of the j th pump in a logarithmic scale, P d0 (j,t) and S L0 (k) denote a pump power and a signal power at a reference operating point, T dL (j,k) corresponds to a linear coefficient relating the forward pump powe adjustment of the j th forward Raman pump and the input signal power varation for the k th wavelength region, S L (k,t−T) denotes a detected input signal power in the k th wavelength region as linearly scaled, and T denotes a determined time delay between a required pump power adjustment and a detected input signal power variation.