Copyright Information: This publication has been posted here to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.

DSL access over a POTS local loop requires accurate characterization of that loop. One approach to this problem is to identify the loop structure first and then simulate and analyze the identified loop. The most important task in the identification process is to estimate the length of twisted-pair segments in local loops. We present an innovative approach based on the loop frequency response. The procedure exploits the assumption that the loop frequency response is a linear combination of complex sinusoids, utilizing the MODE-Type algorithm (Cedervall, Stoica & Moses, 1995). Numerical simulation results are included to illustrate the accuracy that can be achieved.