Macro-bend Sensor Research Articles

Optical Strain Gauge-Based on a Hetero-Core Fiber Macro-Bending Sensor

This paper describes a novel approach for optical strain sensing based on a hetero-core fiber optic macro-bending sensor. A gauge substrate for the proposed sensor was designed to transduce the tensile and compression strain by changing to a gentle bending curvature on the fiber; thus, the hetero-core fiber detects the strain on the substrate as the transmitted light lost. Because optical fibers perform as a flexible structure in a buckling scheme owing to their slenderness, the mechanical properties of the proposed sensor can be widely tuned by the shape and mechanical properties of the gauge substrate. Experiments demonstrated that the proposed strain gauge with a spring-structured substrate made of SUS304 showed a strain applied within $\pm 3100~\mu \epsilon $ with a sensitivity of up to $- 9.14\times 10^{-4}$ dB/ $\mu \epsilon $ , and responded to temperature changes from 0 °C to 60 °C with $- 1.10\times 10^{-2}$ dB/°C owing to the thermal expansion of the substrate. Furthermore, both the strain and temperature sensitivities are tunable by changing the geometrical parameters of the gauge substrate.

Sensitivity enhancement of singlemode-multimode-singlemode fiber optic sensor based on macrobending effect for food composition monitoring

The paper analyzes the sensitivity enhancement of the Fiber Optic Sensor (FOS) based on the Singlemode-Multimode-Singlemode (SMS) structure for food composition monitoring. The enhancement method utilized in this refractive index sensor is the macrobending effect with bending diameter of 2.8, 3.3 and 4 cm. The sensitivity of the sensor were analyzed in different food liquids such as water, oil and 1.0 mol sugar, with the refractive index of 1.333, 1.384 and 1.464 respectively. The device was developed using the fusion arc splicing technique and etching process of the sensor’s area. The selected core diameter of the sensor’s area according to the etching process analysis was 55 µm at etching time of 15 minutes. The results of the sensor with and without the macrobending effect were observed. Meanwhile, the smallest bending diameter experienced the highest sensitivity. Overall, the experiment demonstrated an improved sensitivity of the macrobending sensor by 38.14%. This study broadens the potential of the simple sensor configuration for application in food composition monitoring.

Optical Fiber Sensors Embedded Into Medical Textiles for Healthcare Monitoring

The potential impact of optical fiber sensors embedded into medical textiles for the monitoring of respiratory movements in a magnetic resonance imaging environment is presented. We report on three different designs, all textile based: a macrobending sensor, a Bragg grating sensor, and a time reflectometry sensor. In all three cases, the sensing principle is based on the measure of the elongation of the abdominal circumference during breathing movements. We demonstrate that the three sensors can successfully sense textile elongations between 0% and 3%, while maintaining the stretching properties of the textile substrates for a good comfort of the patients.

Macrobend sensor via the use of a hollow-core splice fiber: theory and experiments

The characteristics of the use of a hollow-core splice scheme for macrobend measurements are discussed both theoretically and experimentally. A perturbation theory for the modes of a bent hollow-core fiber and its loss characterization are developed so as to better understand the characteristics of the scheme. The maximal detection range of fabricated sensors with the proposed scheme is experimentally determined to be as large as a few hundred millimeters relative to the radius of curvature. In addition, the numerical estimation of the loss characteristics using the scheme shows modal trends which are in good agreement with experimental data.

A simple fiber-optic sensor for use over a large displacement range

An intensity-based fiber-optic displacement sensor has been developed and tested for static and dynamic response. The sensor incorporates an extremely simple design, light source and detector. Testing was done using quasi-static extension, a simple oscillating cantilever beam and a small shaker capable of frequencies up to 10 kHz. The sensor shows a response over a wide range of 410 mm. The response has two distinct linear regions with a central nonlinear region. For small displacements, the sensor shows excellent frequency response up to 10 kHz. At this stage, no attempt has been made to theoretically predict the light-loss behavior associated with this macrobend sensor [Marcuse, D., Journal of the Optics Society of America, 66 (3) (1976) 216–220; Lagakos, N., Cole, J. H. & Bucaro, Applied Optics, 26 (11) (1987) 2171–2180]; 1,2 rather this paper serves to demonstrate the basic function of the novel geometry of the sensing element.