The use of Walsh code in modulating the pump light of high spatial resolution phase-shift-pulse Brillouin optical time domain analysis with non-return-to-zero pulses

We have previously reported phase modulation of pump light of phase-shift pulse Brillouin optical time domain analysis with non-return-to-zero (NRZ)-formatted Golay codes. However, the Brillouin signal has been distorted when the duration of the coded pulse used exceeds the time constant of the ampl...

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Bibliographic Details
Published in:Measurement science & technology 2013-09, Vol.24 (9), p.94025-1-13
Main Authors: Zan, Mohd Saiful Dzulkefly Bin, Tsumuraya, Tatsuya, Horiguchi, Tsuneo
Format: Article
Language:English
Subjects:
BOTDA
Brillouin zone
Distortion
fiber sensor
Golay codes
Mathematical analysis
Modulation
Pumps
Spatial resolution
stimulated Brillouin scattering (SBS)
Time domain analysis
Walsh codes
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Summary:We have previously reported phase modulation of pump light of phase-shift pulse Brillouin optical time domain analysis with non-return-to-zero (NRZ)-formatted Golay codes. However, the Brillouin signal has been distorted when the duration of the coded pulse used exceeds the time constant of the amplitude in the acoustic wave that causes stimulated Brillouin scattering. Therefore, we propose pump modulation with Walsh codes to overcome this problem. We have shown that the use of Walsh codes in the NRZ-formatted pump induces little error in the spatial resolution, contrary to the previous results for Golay codes. The maximum signal-to-noise ratio improvement for 8-bit Walsh codes recorded was 3 dB and the spatial resolution obtained was 10 cm, being consistent with analytical and numerical calculations.
ISSN:0957-0233
1361-6501
DOI:10.1088/0957-0233/24/9/094025