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This paper presents a technique that significantly simplifies the design and operation of transparent optical wavelength-division-multiplexing (WDM) networks. Since most of the signal degradations arise due to the interaction of linear and nonlinear physical effects along the fiber links, a link design concept based on erbium-doped fiber amplification is developed and optimized such that originally degrading effects mutually compensate each other, leading to approximately noise-limited transmission. In extensive numerical simulations as well as laboratory experiments, an optimized modular link design is identified. Regenerator-free transmission of a single-channel 10-Gb/s nonreturn-to-zero signal over 4000 km is achieved in a recirculating loop experiment with less than a 3-dB penalty. Reliable WDM transmission is demonstrated over 1600 km, showing the high robustness of this concept. Finally the link design concept is applied in a WDM field trial using deployed standard single-mode fibers (S-SMFs) of the optical network infrastructure of Deutsche Telekom. Between the German cities of Berlin and Darmstadt, 10-Gb/s synchronous digital hierarchy (SDH)-based data, 10-Gb/s duobinary-encoded data, and a native Gigabit Ethernet signal have been transmitted error-free over a maximum distance of 1720 km, thus demonstrating the feasibility of the design concept under realistic field conditions. The presented design approach substantially supports link setup and rerouting procedures by supplying simple rules to identify the maximum number of dispersion-compensated S-SMF amplified spans which can be cascaded for a given tolerable penalty.