Abstract: An optical WDM transmission system. The arrangement includes a splitter for dividing a multiplexed optical signal having a prescribed bandwidth into a plurality of distinct sub-bands. The plurality of distinct sub-bands is received by a plurality of output paths, respectively, which direct the sub-bands to respective ones of a plurality of optical amplifiers disposed in the output paths. The optical amplifiers each have a prescribed gain shape across the bandwidth of its respective sub-band. A coupler recombines the distinct sub-bands and couples them onto the optical fiber transmission path. An optical preamplifier is coupled to an input of the splitter. The optical preamplifier is a Raman amplifier having a bandwidth substantially encompassing the prescribed bandwidth of the multiplexed optical signal.

Abstract: A method is provided for determining at least one optical transmission parameter for achieving a prescribed operating characteristic of an optical transmission system that includes at least one optical amplifier. The optical transmission parameter to be determined may include, for example, the channel wavelengths that are employed, the channel powers, and/or the spacing between adjacent channels.The method begins by transmitting through the transmission system a plurality of saturating optical wavelengths such that the optical amplifiers operate at a desired operating point within a region of gain compression. A plurality of probe wavelengths are transmitted through the transmission system. The probe wavelengths have a total power insufficient to substantially change the desired operating point of the optical amplifiers. The plurality of probe wavelengths are characterized by at least one optical transmission parameter. Next, an initial operating characteristic of the transmission system is determined.