Optical transmission systems of the present invention include at least one optical amplifier configured to provide optical amplification of one or more information carrying optical signal wavelengths. At least one optical amplifier is controlled based on an in situ performance characterization of the at least one optical amplifier and the transmission fiber. The in situ, or installed, performance characteristics of the optical amplifier can be characterized based on relative gain measurements over the signal wavelength range as a function of the supplied pump power. The installed characterization allows the optical amplifier performance and gain profiles to be tightly controlled over the signal wavelength range in the transmission system.