On using various local loop types in recent VDSL applications

This paper presents a simple comparison between line conditions produced by using two types of local loops which operate in VDSL (Very-high-bit-rate speed Digital Subscriber line) environment. The object of observation is copper transmission line that remains in access network after replacing copper wires from CO (Central Office) to DP (Distribution Point) with optical fibres, i.e. after implementing a FTTB (Fibre to the Building/Basement) solution. Two borderline loop types from opposite edges are used: purposefully manufactured DSL indoor cable and ordinary flat telephone indoor cable. The paper gives at first a short overview of previously introduced and verified short loop model in DSL, followed by brief description of its leading testing scenarios. After that, major testing scenarios are implemented on two observed loop types under same conditions. An explanation of obtained results with appropriate discussion is done at the end. Primary loop coefficients and transfer functions are used as observed quantities. All results of measurements and observations are collecting on real system in operation conditions.