scholarly journals The Influence of Laser Linewidth on the Brillouin Shift Frequency Accuracy of BOTDR

2018 ◽  
Vol 9 (1) ◽  
pp. 58 ◽  
Author(s):  
Qing Bai ◽  
Min Yan ◽  
Bo Xue ◽  
Yan Gao ◽  
Dong Wang ◽  
...  
Keyword(s):  
Probe Pulse ◽  
Measurement Accuracy ◽  
Signal To Noise Ratio ◽  
Gain Spectrum ◽  
Laser Source ◽  
Laser Linewidth ◽  
Optical Time Domain Reflectometer ◽  
Brillouin Gain ◽  
Optical Time ◽  
Shift Frequency

This paper analyzes the influence of laser linewidth on the measurement accuracy of a frequency-scanning Brillouin optical time domain reflectometer (FS-BOTDR), allowing for both the width of Brillouin gain spectrum and the signal-to-noise ratio (SNR) of the BOTDR system. The measurement accuracy of the Brillouin frequency shift (BFS) is theoretically investigated versus the duration of the probe pulse and the linewidth of the laser source, by numerically simulating how a FS-BOTDR works and evaluating the Brillouin gain spectrum (BGS) width and the system SNR. The simulation results show that the BFS accuracy is improved as the laser linewidth becomes narrower when the probe pulse width is fixed. We utilize five types of lasers with respective linewidths of 1.05 MHz, 101 kHz, 10.2 kHz, 3.1 kHz, and 98 Hz to compare the BFS measurement accuracy over a ~10 km optical sensing fiber. The experimental results demonstrate that the root-mean-square error (RMSE) of BFS decreases with the laser linewidth narrowing from 1.05 MHz to 3.1 kHz, which is in good agreement with the numerical simulation. However, the RMSE of BFS increases when the laser linewidth is less than 3.1 kHz, which may arise from the coherent Rayleigh noise due to a too narrow laser linewidth. The results can provide a theoretical basis and experimental guidance for choosing the appropriate laser linewidth in BOTDR.

scholarly journals Improvement of Performance for Raman Assisted BOTDR by Analyzing Brillouin Gain Spectrum

Sensors ◽  
2021 ◽  
Vol 22 (1) ◽  
pp. 116
Author(s):  
Qiang Huang ◽  
Junqiang Sun ◽  
Wenting Jiao ◽  
Li Kai
Keyword(s):  
Spatial Resolution ◽  
Measurement Accuracy ◽  
Gain Spectrum ◽  
Analysis Method ◽  
Optical Time Domain Reflectometer ◽  
Starting Point ◽  
First Occurrence ◽  
Brillouin Gain ◽  
Optical Time ◽  
The Mathematical Model

We propose a simplified partitioned Brillouin gain spectrum (BGS) analysis method to enhance the spatial resolution and measurement accuracy of a Brillouin optical time-domain reflectometer (BOTDR) assisted by a first-order Raman pump. We theoretically derive the mathematical model of the partitioned BGS and analyze the superposition process of sub-Brillouin signals within a theoretical spatial resolution range. We unified all the unknown constant parameters of the calculation process to simplify the partitioned BGS analysis method and the value of the uniform parameter is attained through the system test data and numerical analysis. Moreover, to automate data processing, the starting point of the temperature/strain change is determined by the first occurrence of the maximum Brillouin frequency shift (BFS), then the position where the partitioned BGS analysis method calculation begins is obtained. Using a 100 ns probe pulse and partitioned BGS analysis method, we obtain a spatial resolution of 0.4 m in the 78.45-km-long Raman-assisted BOTDR system, and the measurement accuracy is significantly improved. In addition, we achieve a strain accuracy of 5.6 με and a spatial resolution of 0.4 m in the 28.5-km-long BOTDR without Raman amplification.

scholarly journals Pulse-Width Multiplexing ϕ-OTDR for Nuisance-Alarm Rate Reduction

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3509 ◽  
Author(s):  
Xiang Zhong ◽  
Xicheng Gao ◽  
Huaxia Deng ◽  
Shisong Zhao ◽  
Mengchao Ma ◽  
...  
Keyword(s):  
Pulse Width ◽  
Signal To Noise Ratio ◽  
Fusion Algorithm ◽  
Multisensor Data Fusion ◽  
Optical Time Domain Reflectometer ◽  
Light Pulses ◽  
Phase Sensitive ◽  
Evidential Theory ◽  
Vibrating Table ◽  
Optical Time

A pulse-width multiplexing method for reducing the nuisance-alarm rate of a phase-sensitive optical time-domain reflectometer ( ϕ -OTDR) is described. In this method, light pulses of different pulse-widths are injected into the sensing fiber; the data acquired at different pulse-widths are regarded as the outputs of different sensors; and these data are then processed by a multisensor data fusion algorithm. In laboratory tests with a sensing fiber on a vibrating table, the effects of pulse-width on the signal-to-noise ratio (SNR) of the ϕ -OTDR data are observed. Furthermore, by utilizing the SNR as the feature in a feature-layer algorithm based on Dempster–Shafer evidential theory, a four-pulse-width multiplexing ϕ -OTDR system is constructed, and the nuisance-alarm rate is reduced by about 70%. These experimental results show that the proposed method has great potential for perimeter protection, since the nuisance-alarm rate is significantly reduced by using a simple configuration.

Influences of laser source on phase-sensitivity optical time-domain reflectometer-based distributed intrusion sensor

2014 ◽  
Vol 53 (21) ◽  
pp. 4645 ◽  
Author(s):  
Xiang Zhong ◽  
Chunxi Zhang ◽  
Lijing Li ◽  
Sheng Liang ◽  
Qin Li ◽  
...  
Keyword(s):  
Time Domain ◽  
Laser Source ◽  
Phase Sensitivity ◽  
Optical Time Domain Reflectometer ◽  
Optical Time ◽  
Time Domain Reflectometer

Brillouin gain spectrum manipulation using multifrequency pump and probe for slope-assisted BOTDA with wider dynamic range

2022 ◽  
Author(s):  
Kazuki Hoshino ◽  
Daiki Saito ◽  
Yuma Endo ◽  
Takahiro Hasegawa ◽  
Yosuke Tanaka
Keyword(s):  
Dynamic Range ◽  
Time Domain Analysis ◽  
Gain Spectrum ◽  
Optical Pulses ◽  
Shaping Technique ◽  
Pump And Probe ◽  
Spectral Components ◽  
Brillouin Gain ◽  
Linear Slope ◽  
Optical Time

Abstract We propose slope assisted Brillouin optical time domain analysis (SA-BOTDA) with virtual Brillouin gain spectrum (BGS) generated by multifrequency pump and probe. The virtual BGS having a wide linear slope region of 100 MHz is easily generated by employing time-to-space spectral shaping technique that has been originally developed for generating short optical pulses. We demonstrate the distribution of virtual BGS realized by using five spectral components of pump and probe.

scholarly journals Measurement Accuracy Enhancement via Radio Frequency Filtering in Distributed Brillouin Sensing

Sensors ◽  
2019 ◽  
Vol 19 (13) ◽  
pp. 2878 ◽  
Author(s):  
Cheng Feng ◽  
Stefan Preussler ◽  
Jaffar Emad Kadum ◽  
Thomas Schneider
Keyword(s):  
Radio Frequency ◽  
Noise Reduction ◽  
Measurement Accuracy ◽  
Signal To Noise Ratio ◽  
Rf Filters ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass ◽  
Optical Time ◽  
Rf Signal

In this article, we demonstrate the noise reduction and signal to noise ratio (SNR) enhancement in Brillouin optical time-domain analyzers (BOTDA). The results show that, although the main noise contribution comes from the Brillouin interaction itself, a simple low pass filtering on the detected radio frequency (RF) signal reduces remarkably the noise level of the BOTDA traces. The corresponding SNR enhancement depends on the employed cut-off frequency of the low pass filter. Due to the enhancement of the SNR, a mitigation of the standard deviation error of the Brillouin frequency shift (BFS) has been demonstrated. However, RF filters with low cut-off frequency could lead to distortions on the trace signals and therefore detection errors on a non-uniform BFS. The trade-off between the noise reduction and the signal distortion as well as an optimal cut-off frequency are discussed in detail.

scholarly journals Effects of Pump-Pulse Width and Temperature on Experimental Brillouin Gain Spectrum Obtained from Brillouin Optical Time-Domain Analysis Sensors

2020 ◽  
Vol 27 (1) ◽  
pp. 69-80
Author(s):  
Abul Kalam Azad
Keyword(s):  
Pump Pulse ◽  
Time Domain ◽  
Pulse Width ◽  
Nonlinear Least Squares ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Gain Spectrum ◽  
Least Squares Curve Fitting ◽  
Brillouin Gain ◽  
Optical Time

In this paper, the characteristics of Brillouin gain spectrum (BGS) obtained from a Brillouin optical time-domain analysis (BOTDA) sensor are investigated and analyzed experimentally. The measured BGSs obtained for various pump-pulse widths and temperatures are fitted with different spectrum profiles using nonlinear least-squares curve fitting technique. The fitting performances of used profiles are presented and analyzed. Based on such performances, the proper spectrum profile to be used in the fitting process is determined and used to extract key parameters of the measured BGSs accurately. The variations of such key parameters with pump-pulse widths and temperatures are also investigated and analyzed. The results reveal that pump-pulse widths and temperatures have significant effects on the extracted key parameters of the measured BGSs obtained from BOTDA sensors. Bangladesh Journal of Physics, 27(1), 69-80, June 2020

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