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Temperature and strain discrimination is experimentally demonstrated in an elliptical-core polarization-maintaining fiber by making use of Rayleigh-based distributed birefringence measurements and the frequency shift of the correlation peak obtained by standard coherent optical time-domain reflectometry. The high sensitivity of coherent Rayleigh sensing and the very distinct behavior of birefringence...
The round trip time of the light pulse limits the maximum detectable frequency response range of vibration in phase-sensitive optical time domain reflectometry (φ-OTDR). We propose a method to break the frequency response range restriction of φ-OTDR system by modulating the light pulse interval randomly which enables a random sampling for every vibration point in a long sensing fiber. This sub-Nyquist...
This paper presents the first report on on-line and final blind field test results of a pipeline integrity threat surveillance system. The system integrates a machine+activity identification mode, and a threat detection mode. Two different pipeline sections were selected for the blind tests: One close to the sensor position, and the other 35 km away from it. Results of the machine+activity identification...
A novel liquid-level sensing system based on differential pulse-width pair Brillouin optical time domain analysis technology with a self-heated high attenuation fiber (HAF) is proposed and demonstrated in this paper, where the principle is to measure the temperature abruption position at the interface between liquid and air caused by the different thermal diffusion rates of the two kinds of mediums...
The thermomechanical behavior of a standard optical fiber with double coating is theoretically analyzed at room temperature and ∼ 220 K. As the primary coating becomes stiffer at low temperature, the impact of the thermal expansion of the coatings is no longer negligible and contributes to the thermal response of the fiber sensor. The temperature sensitivity enhancement is validated by distributed...
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