Patent ID: 6977772

Claim:
A direct optical amplifier for establishing a correlation between the average level of a main signal having a plurality of channels and the level of a pilot tone signal for controlling the average level of said main signal to a desired level, said direct optical amplifier comprising: optical amplification means for amplifying the main signal and the pilot tone signal; pumping light generation means for generating pumping light that optically pumps said optical amplification means; wavelength analysis means for analyzing the spectral intensity of an optical transmission signal that includes the main signal and the pilot tone signal and extracting the level of the pilot tone signal and the average level of the main signal from which a noise component has been eliminated; pilot tone signal monitor means for monitoring the level of the pilot tone signal that has been extracted by said wavelength analysis means; main signal monitor means for monitoring the average level of the main signal from which a noise component has been eliminated and which has been extracted by said wavelength analysis means; processing means for establishing a correlation between the level of the pilot tone signal that is monitored by said pilot tone signal monitor means and the average level of the main signal from which the noise component has been eliminated and which is monitored by said main signal monitor means, determining the level of the pilot tone signal that corresponds to a desired average level of the main signal from which the noise component has been eliminated; and taking this pilot tone signal level as a target level; and pumping light control means for controlling the intensity of the pumping light that is generated by said pumping light generation means and adjusting the amplification factor of said optical amplification means such that the level of the pilot tone signal that is monitored by said pilot tone signal monitor means becomes said target level that is determined at said processing means.