System and method for characterizing the performance of data communication systems and devices

In one aspect, the present invention is a technique of, and a system and sensor for measuring, inspecting, characterizing and/or evaluating the performance of high-speed data communication systems, and components used therein. In one embodiment, the present invention measures, inspects, characterizes and/or evaluates the performance, for example the ER, of such systems and/or components in situ-that is, in the environment and/or in the configuration in which the system and/or components are used during normal or typical operation (for example, when the system and/or component is transmitting and receiving user data). In this way, a more accurate representation of the performance of the system (and components thereof) may be measured, detected, determined and/or obtained.