Research of Haar wavelet threshold sensitivity for detection non-reflective events on fragments of OTDR traces

摘要

This work is concerned with research of Haar wavelet threshold sensitivity for detection of non-reflective events corresponding to optical fiber fusion splices on fragments of fiber optic link traces measured by optical time domain reflectometer (OTDR). We performed test series contained 40 step-by-step repeatable splicing of the same couple of standard singlemode fibers of ITU-T Rec. G.652 spools with length 2.2 km and 4.2 km and outer termination by conventional singlemode FCAJPC pigtails for OTDR connection and following bidirectional trace measurement. Results of insertion loss estimation and accomplished by OTDR software automated detection of non-reflective event corresponding to fusion splice of described optical fibers as well as ability of its visual manual localization on trace were recorded. The first 30 splices were realized by fusion splicer conventional program for jointing standard singlemode optical fibers of ITU-T Rec. ITU-T G.652, while the next 10 splices were done under "attenuator" mode with preset increased insertion loss. Described link traces were measured by OTDR operating in a standard mode with high spatial resolution under pulse width 20 ns and appropriate dynamic range with far-end OSNR 6.5 dB at wavelength 1550 nm. As a result 80 traces were analyzed in both automated and manual modes with fusion splice insertion loss varied from 0.002 dB to 0.554 dB. At the next stage we applied continues Haar wavelet transform for detection non-reflective event on measured traces of lab fiber optic link containing described one fusion splice with total length about 6.4 km. According to results, wavelet transform of described link trace provides detection of extremely low loss non-reflective events with OTDR reading down to own error corresponding to 0.020...0.030 dB range under improved scaling over normalized spatial diagram of wavelet coefficients.