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 the performance of high-speed data communication systems, and components used therein. In one embodiment, the present invention measures the performance, for example the error rate 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). For this purpose a system parameter, e.g. the signal amplitude, is set to different levels, for each level an error rate is determined, and the final error rate is determined, and the final error rate is determined through extrapolation. In this way, a more accurate representation of the performance of the system (and components thereof) may be determined.