Single-Ended Loop Testing (SELT) - New Architecture

Nowadays the embedded copper plant is revitalized for digital subscriber lines (DSL), and identification of the loop make-up is vital for determining what types of DSLs may be deployed and what bit rates they may transmit. Single ended loop testing (SELT) is new emerged loop test and qualification technology. It´s essential for achieving low-cost deployment of DSL, since it allows loops to be qualified in bulk and does not involve any human intervention at the customer´s location. Though there are several approaches and tools can realize SELT, most of them can´t incorporate with DSL chipsets. This paper proposes a novel technique, which can be easily incorporate with the DSL chipsets and accurately qualify a telephone lines. This measurement technique is accord with the Gselt functional model which is proposed by ITU. The measurement technique consists of energizing the line with a spread spectrum signal through the line that is reflected back at the discontinuity. Use correlation length measuring principle by calculate the correlation between the reflected signal and the original transmitted signal it is easy to get the knowledge of the loop make-up. Then in addition using a direct measurement of the PSD it can pre-qualify the loop.