Abstract
In this paper, a long-distance distributed pressure sensing system based on a special fiber and using frequency-scanned phase-sensitive optical time-domain reflectometry is proposed. The fiber shows high pressure sensitivity (159 MHz/bar) and low loss (3 dB/km) owing to its simple structure made of two large air holes in the cladding. The pressure response of the two orthogonal polarization axes of the fiber is explored distinctively. Distributed pressure sensing over a long sensing range (720 m) and high spatial resolution (5 cm) is demonstrated, resulting in 14,400 resolved sensing points with uncertainty on pressure of 0.49 bar. Discrimination between the temperature/strain and pressure responses is demonstrated, taking advantage of the different pressure and temperature sensitivities of the two polarization axes. In addition, the temperature response of the fiber is studied and the simulation results show the possibility of scaling the temperature sensitivity by adjusting the size of the core. The sensing distance limit due to crosstalk between the polarization axes is also discussed.
Highlights
Distributed fiber sensing (DFS) has drawn much attention since it provides a cost effective solution by sensing information from thousands of or even millions of locations using just one interrogator and a single fiber, instead of deploying a complex sensor array
Long-distance distributed pressure sensing with high spatial resolution After the characterizations of the fiber sensitivities, we reduced the pulse width to 500 ps (i.e.5 cm spatial resolution) to bring the system to its ultimate performance
We propose a distributed pressure sensing based on Φ-OTDR and a special fiber with elliptical core and 2 side air holes in the cladding
Summary
Distributed fiber sensing (DFS) has drawn much attention since it provides a cost effective solution by sensing information from thousands of or even millions of locations using just one interrogator and a single fiber, instead of deploying a complex sensor array. Traditional DFSs using standard single mode fibers (SMF) are mostly focused on temperature and axial strain sensing. A few distributed pressure sensing (DPS) schemes have been proposed based on Brillouin scattering using fibers with special coatings [12,13,14], dynamic gratings [15,16] or optical frequency-domain reflectometry (OFDR) [17,18,19], demonstrating the great potential of DPS using DFS technology. Either the pressure sensitivity is relatively low due to the large Young’s modulus of the fiber material silica [12,13,14,15,16], or the sensing range is fundamentally limited by the sensing range of OFDR [17,18,19]
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