Subpeaks in the Brillouin loss spectra of distributed fiber-optic sensors were observed for what is believed to be the first time and studied. We discovered that the Fourier spectrum of the pulsed signal and the off-resonance oscillation both contributed to subpeaks. The off-resonance oscillation at frequency is the oscillation in the Brillouin time domain when beat frequency ν of the two counterpropagating laser beams does not match local Brillouin frequency . This study is important in differentiating the subpeaks from actual strain–temperature peaks.
© 2005 Optical Society of America
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