Techniques are disclosed for computing distance-to-fault (DTF) in communication systems. The techniques can be embodied, for instance, in a DTF system that provides a multi-port probing device and DTF functionality, including computing distances to faults and the fault magnitudes. In addition, the DTF system is further configured with the ability to accurately measure complex reflection coefficient of the UUT, and/or return loss of the UUT. The complex reflection coefficient and/or return loss of the UUT can be computed as a function of known scattering parameters of a multi-port measurement circuit included in the probe of the DTF system.