Patent ID: 7248398

Claim:
A method for determining a gain spectrum for a Raman amplifier located downstream from an optical fiber amplifier in a WDM transmission system, comprising: switching the Raman amplifier into one respective amplifier state selected from an on state and an off state; measuring an optical spectra at an output of the Raman amplifier with a pumping source when the optical fiber amplifier is switched into an active state to cause amplified spontaneous emission; and determining the gain spectrum from these spectra, wherein a first spectrum is measured with the pumping source for the Raman amplifier switched off and the pumping source for the optical fiber amplifier switched on, a third spectrum is measured with the pumping source for the Raman amplifier switched on and the pumping source for the optical fiber amplifier switched on, and the gain spectrum for the Raman amplifier is calculated according to the following rule: Gain Spectrum=(Third Spectrum)/(First Spectrum).