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• The biggest innovation of this paper is that SPR is excited in ARF by numerical analysis for the first time. • In this paper, the detailed optimization process of optical fiber performance is given, and the optimal structural parameters are obtained. • The proposed ARF-SPR refractive index sensor has two formants, both of which can detect analytes with refractive index ranging from 1.31 to 1.445, and the maximum wavelength sensitivity of the two formants can reach 20000 nm/RIU and 36400 nm/RIU, respectively. • The structure is filled with gold in the negative curvature tube to excite SPR, which reduces the manufacturing difficulty compared with the traditional coating method. Owing to advances in the surface plasmon resonance (SPR) technology, sensors composed of photonic crystal fibers (PCFs) based on SPR have attracted extensive attention. Herein, a double-formant SPR refractive index sensor comprising the anti-resonant fiber (ARF) is designed and analyzed, which can be used to realized high sensitivity and wide detection range. SPR is excited by gold filling in the negative curvature tube and replaces the traditional coating process to reduce the difficulty associated with actual production. Finite element analysis indicates that the optimized ARF-SPR sensor can detect analytes in the refractive index range of 1.310–1.445 with a maximum wavelength sensitivity and amplitude sensitivity of 36400 nm/RIU and 2,573.33 RIU−1, respectively. In addition, the minimum resolution and structural parameter sensitivity is 2.747 × 10-6 RIU and 38 nm/μm. The maximum figure of merit (FOM) is 776.15 RIU−1, and as the refractive index of the analyte increases, the length of the sensor decreases, which suggesting great potential in biochemical detection and geological exploration. [ABSTRACT FROM AUTHOR]

Abstract: Both the changes in temperature and strain during the process are used to reveal serious seepages and settlements occurring inside the embankment dam. A method for seepage and settlement monitoring in earth embankment dams using fully distributed sensing along optical fibres is proposed. The proposed monitoring system also offers the owner the strategy of the inspection and maintenance in earth embankment dams. The database in the control and maintenance center is described. In this paper, as an example, a model filled with the soil from Yellow River is built and bare optical fibers are embedded under different soil layers near the seepage path. The configuration of optical sensing cable in series of embankment dams is developed. The simulated seepage flows under various flow rates are monitored using the optical fibers and measured by a DiTeSt –STA202 distributed temperature and strain analyzer. A partial settlement within the embankment dam model is observed. The continuously decreasing temperature curve shows an abrupt dramatic increasing rate, which shows that the change is not caused by the temperature of the seepage water but the strain. The information from the monitoring center provides important reference for the expert decision-making system to ensure the safety of the embankment dam long running. [Copyright &y& Elsevier]