In this paper, stimulated Brillouin scattering induced noise in Brillouin optical time domain analyzers is experimentally and theoretically investigated. The noise mainly comes from the beating between the probe wave and the spontaneous Brillouin scattering component and from phase-to-intensity conversion. The noise in the time and frequency domain has been measured along the fiber. The results reveal that, compared to gain based sensors, the loss based ones show a lower Brillouin induced noise level. Furthermore, the Brillouin noise is characterized in dependence on the spatial resolution. This investigation provides a deep insight to the frequency dependence of the noise distribution, which might contribute to signal-to-noise ratio enhancement in Brillouin-based distributed sensing.
KEYWORDS: Signal detection, Electronic filtering, Linear filtering, Signal to noise ratio, Sensors, Radio optics, Interference (communication), Fiber Bragg gratings, Denoising
This paper presents and experimentally demonstrates a new approach for the noise reduction and measurement accuracy enhancement in Brillouin optical time domain analyzers (BOTDA) by applying low pass filtering to the detected radio frequency (RF) signal. The simulation and experimental results indicate that the noise level of the BOTDA traces is reduced by using RF filtering. The corresponding measurement accuracy improvement depends on the cut-off frequency of the employed low pass filter. RF filtering is more efficient than other post-processing methods since it overcomes the long processing time. However, the results also imply that RF filters with too low bandwidths distort the trace signals and lead to detection errors.
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