Application of statistical inference to optical time domain reflectometer data
AssigneeAT&T Corp.
InventorsMichael Asher, Hossein Eslambolchi, Chuck Giddens, John Sinclair Huffman, Harold Stewart
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Abstract
The present invention relates to a method for interpreting data obtained by measuring a length of optical fiber using an optical time domain reflectometer (OTDR), and comparing that measurement to a reference measurement. The technique uses statistical inference to determine a whether a reference trace is valid by comparing that trace to a more recent test trace. The reference trace may be replaced or an alarm may be transmitted under certain conditions.
Claims9
A method for monitoring reflective characteristics in an optical fiber, by comparison to a reference trace stored in a memory, the method comprising the steps of:
- receiving parameters from a test OTDR trace Ttest of the optical fiber;
- retrieving from the memory parameters from a reference OTDR trace Tref;
- determining whether the reference OTDR trace Tref is valid and whether an alarm condition exists by comparing the test OTDR trace Ttest with the reference OTDR trace Tref using a statistical comparison;
- and
- if the reference OTDR trace Tref is valid and an alarm condition exists, then:
- (a) conducting a one-sample z-test on an array IL[ ]test of instantaneous loss values of the test OTDR trace Ttest;
- and
- (b) making a fault-type determination from the z-test of whether the alarm condition is likely due to a point fault or a cumulative fault;
- and
- (c) transmitting the alarm and the fault-type determination.
Dependencies are inferred from the claim text.