The introduction of new services (such as multimedia communications, video conferencing, distance learning) is creating a rapid increase in telecommunication traffic. This is leading to the need for higher-capacity transmission networks, with information transport over the network links at rates of tens and hundreds of gigabits per second. Due to processing-speed limitations of electronic cross-connects, optical cross-connects based on wavelength division multiplexing (WDM) is the current technology of choice for realizing a high-capacity backbone to be superimposed on top of the existing electrical transport layer. In a WDM network, the use of multiple optical frequencies has the effect that signals at different wavelengths act as interferers to a specific optical wavelength being received. We describe a three-node WDM ring network and characterize the bit-error rate at a specific wavelength as a function of optical power from "interfering" wavelengths in a typical receiver that would be used in a WDM system.