British Telecommunications Public Limited Company

Daniel Gilks

Feiyu Fang

Lykourgos Kekempanos

Marco Menchetti

Liam Bussey

Fraser Ashley Burton

Philip M Bull

A method of determining when there has been a change in the modem power state of a modem connected to a digital subscriber line. An Uncalibrated Echo Response (UER) trace is obtained from the digital subscriber line by running a Single Ended Line Test (SELT) on the line. This UER trace is compared to a historical (baseline) UER trace from the same line. A difference in the two traces in a higher frequency range (for example, DS3 for a VDSL line), is indicative of a possible modem power state change.

Detecting modem power state change

A method of determining the location of a disconnection on a digital subscriber line, in particular a VDSL line, where the line has a number of nodes or connection points along it. A statistical model is generated from a population of lines that maps the loop (line) lengths of each of those lines obtained by line test measurements (such as single ended line test traces—SELT traces) against the corresponding loop lengths obtained from inventory data. The model is then used to determine a predicted loop length by mapping a measured loop length (taken from line test measurements) onto an inventory loop length using the model. Knowledge of the node positions on the line is then used to give a probability a line disconnect occurring at a given node by mapping the predicted loop length onto the node positions.

DSL fault location

Presented is a method of detecting a loop length change in a digital subscriber line. An Uncalibrated Echo Response (UER) trace is obtained from the digital subscriber line by running a Single Ended Line Test (SELT). A historical (baseline) UER trace from the same line is retrieved. A line that has experienced a small change in loop length will have the same overall shape, but be compressed or stretched in the frequency domain. Thus, to detect such a change, a comparison between the two traces is made to determine if the difference between the two traces is less than a threshold but non-zero. Then a range of scale factors are applied in the frequency domain on either one of the traces, before determining which of the scale factors results in the lowest difference between the unscaled and scaled traces. The determined scale factor is above a certain threshold, then the line is determined to have had a loop length change. The value of the scale factor can be used to determine the amount the length has changed.

Detecting a loop length change in a digital subscriber line

This disclosure provides an optical network, and a method in an optical network, wherein: each reference optical transmitter is configured to transmit a reference optical signal on an associated second optical fiber of a plurality of second optical fibers, each reference error signal generator is configured to generate a reference error signal based on a reflection of the reference optical signal on the associated second optical fiber of the plurality of second optical fibers, and each reference phase shifter is configured to apply a phase shift to the first optical signal based on the reference error signal.

Optical network

Interference on DSL (Digital Subscriber Lines) systems can be identified by collecting modem data and determining, for a plurality of time intervals, whether the line is carrying traffic and/or whether there are errors on the line. The presence of interference can be inferred from the correlation of the traffic data and the error data.

Growing community of inventors

London, United Kingdom

Daniel Gilks