Assessment of Methods for Evaluating the Immunity of PCM Regenerators to Near End Crosstalk

Compares two performance measures used to assess the immunity of PCM regenerators to near end crosstalk, viz. the NEXT noise figure and the input signal-to-NEXT noise ratio. The NEXT noise figure is shown to be the superior performance measure, and three methods of measuring this parameter are compared on the basis of their sensitivity to implementation imperfections. It is shown that although a similar test configuration is used for each method, measurement accuracy is dependent on an associated calibration procedure. Numerical simulations indicate that measurement error can be held to 0.5 dB when practical test equipment is used to measure the performance of different commercial regenerators.