Kaiyue Qi

In this paper, we experimentally demonstrated a bending sensor based on Michelson interferometer (MI). The sensor was fabricated by fusion splicing single-mode fiber (SMF) and multimode fiber (MMF) spheres. The improved end-face packaging scheme was adopted to realize the measurement of bending. The advantage of MMF numerical aperture increases the mode field diameter and the number of modes. Fiber bending induces transition between modes, resulting in the generation and fade of fiber modes, achieving the emergence of bending turning points (BTPs). The BTP is defined as the point where the direction of interference dip shift changes due to fiber bending. By observing the direction of interference dip shift during bending, the degree of bending can be intuitively estimated. The simulation results verify the generation and fade of excited modes in the bending MMF peanut-like structure, which are in good agreement with the experimental results. When the sensor is installed in parallel and titled ways, due to the uneven force of the plate in the bending state, it shows the differences in sensitivity, BTP and initial bending response. Further, the BTP can be roughly adjusted by the MMF core diameter, and the deviation of the sensitivity is reflected in the length of the interference arm. Besides, compact size, low cost and low hysteresis make the sensor more competitive in harsh environment applications.

A highly sensitive hybrid structure sensor based on suspended-core fiber (SCF) is proposed for vector curvature and temperature measurement. The sensor is prepared by self-assembly of SCF-based cascaded Fabry-Perot interferometer (cFPI), single-mode fiber (SMF), and fiber Bragg grating (FBG). In view of the asymmetry of the cFPI, theoretical analysis of the beam transmission and spectral characteristics is implemented when the beam is incident from different directions. The two sensing fibers in the triangular distribution sensor will not be located on the neutral plane at the same time, which makes it possible to measure bending in any orientation. The Vernier effect formed by the cFPI enlarges the curvature and temperature sensitivity to −1064.5 pm/m ⁻¹ and 50.7 pm/°C, respectively, without affecting the measurement range. The spectrum shows the opposite spectral response when the sensor bending direction difference is 180°. The sensor overcomes the bottleneck of bending sensitive blind spots in dual-fiber sensing. In addition, the sensor maintains a smaller size and more flexible preparation, which is conducive to its application in artificial intelligence, medical detection.

A novel fiber Fabry-Perot interferometer (FPI) vector curvature sensor based on Vernier effect is proposed and demonstrated. The triangular-distributed sensing structure is fabricated by self-assembly of FPI and single-mode fiber (SMF). When the device is bent in any orientation, a direction-dependent wavelength shift of the interference pattern is produced because the sensing fiber always deviates from the neutral plane. In order to overcome the trade-off between high sensitivity and large dynamic range, we connect the reference fiber and the sensing fiber to produce the Vernier effect. Without affecting the measurement range of the sensing structure, the sensitivity of the self-assembled sensor based on Vernier effect is amplified by 5 times and 3.6 times respectively by using different FPIs as sensing arm. The experimental results show that the sensing structure has good stability and repeatability. Compared with the substrate packaging, the fiber FPI sensing structure based on self-assembly can realize miniaturization, which is conducive to the application of the sensor in medical detection and artificial intelligence.

Effects of sulfate supplementation on milk yield and composition, ruminal and blood metabolites, acid-base status, and nutrient digestibilities were determined using 30 multiparous, lactating Alpine does. Goats were fed isonitrogenous diets containing .16 (basal), .26, or .36% S (DM basis) during a 13-wk lactation trial that coincided with wk 3 to 15 of lactation. During wk 16 to 17, four does from each treatment were placed in a metabolism crate to measure nutrient digestibility and balance. Feed intake, yield of 4% fat-corrected milk, and milk S content were not affected by added S, but the goats fed the .26% S diet had a trend of higher persistency of lactation (P < .20). During wk 10 and 15 of lactation, milk solids-not-fat percentage was higher (P < .10) for does fed the .26% S diet. Sulfur supplementation resulted in quadratic decreases in ruminal ammonia N (P < .05) in wk 15 and in plasma urea N in wk 10 and 15 (P < .05) but in linear increases (P < .05) in ruminal protein S concentrations throughout the experiment. Added S had little effect on blood acid-base status. Apparent digestibilities of DM, OM, ash, ADF, and GE were increased linearly (P < .10) by added S. The milk N:S ratio remained constant. Increasing S from .16 to .26% of diet DM was beneficial to lactating Alpine goats during early lactation.