Patent ID: 9281892
Filing Date: 2016-03-08
CPC Classification: G01M,H04B

Claim Text:
1. A method of performing fault analysis, performed by an arrangement in a Passive Optical Network (PON), comprising at least one Optical Network Terminal (ONT), by using Optical Time Domain Reflectometry (OTDR), said method comprising: triggering a new OTDR measurement, wherein a previous reference measurement has been made indicating an original state of said PON; inserting an OTDR measurement signal into a multistage splitter before a last splitter stage of said multistage splitter, and wherein said last splitter stage is of ratio 2:Nroot, so that the last splitter stage is connected to a plurality of drop links, and wherein at least one of the plurality of drop links being connected to said multistage splitter comprises at least one sub-splitter, wherein said at least one sub-splitter is of a ratio 1:N determining at least one new event location based on the OTDR measurement signal by analyzing OTDR measurement data, in a predefined sequence, relating to said at least one sub-splitter connected to said last splitter stage starting based on the drop links for which an upstream optical signal needs to travel through the largest number of sub-splitters in order to reach the last splitter stage; and calculating a fault magnitude at a given location by subtracting an event magnitude obtained from the new OTDR measurement from said reference OTDR measurement and taking into account the number of drop links connected to the last splitter stage and to the at least one sub-splitter in the reference measurement and the new measurement, thereby enabling determination of position and severity of said fault locations.