Automatic pump power adjustment for gain-flattened multi-wavelength pumped Raman amplifier

We proposed Raman gain slope measurement method by measuring noise power originated from Raman gain, and pump power adjustment to flatten the gain on various transmission lines by using measured Raman gain slope. We also proposed the technique to vary average gain with flattened profile. Using the techniques, Raman gain profile could be automatically controlled at various average gains according to the characteristics of fibers and the amount of plant loss, without trial and error, as well as without probe signals. As a result, the DAR has come to be free from the troublesome trial and error adjustment onsite, even on various installation conditions.