In this work we demonstrate two new BOTDA sensing systems based on differential (DPSK) and quadrature (QPSK) phase-shift keying modulation techniques with enhanced performances. First we demonstrate Brillouin echoes distributed sensing (BEDS) with centimeter resolution using a single intensity DPSK modulator for the pump pulse. The optical π-phase pulse is directly generated at the end of an intensity pulse using DPSK technique. This allows an easy adjustment of the delay between the intensity and phase pulse and improves the optical loss of the pump. The second technique uses an optical QPSK modulator (I & Q modulator) as a single sideband (SSB) modulator. The advantage of I & Q modulator compared to dual-drive modulator lies on the high performance of carrier suppression of 55 dB as well as side-mode suppression of 40 dB at 1535 nm. Besides the filter that chooses either the Stokes or anti-Stokes component before detecting the Brillouin response on the photodiode is no more needed. By use of the I & Q modulator the performance of BOTDA using either Stokes or anti-Stokes component is shown and discussed.

Date Published: 9 May 2012
PDF: 9 pages
Proc. SPIE 8439, Optical Sensing and Detection II, 843909 (9 May 2012); doi: 10.1117/12.922581

Published in SPIE Proceedings Vol. 8439:
Optical Sensing and Detection II
Francis Berghmans; Anna Grazia Mignani; Piet De Moor, Editor(s)