Triboelectric mechanical sensors—Progress and prospects

In-fiber interferometric-based sensors are a rapidly growing field, as these sensors exhibit many desirable characteristics compared to their regular fiber-optic counterparts and are being implemented in many promising devices. These sensors have the capability to make extremely accurate measurements on a variety of physical or chemical quantities such as refractive index, temperature, pressure, curvature, concentration, etc. This article is a comprehensive overview of the different types of in-fiber interferometric sensors that presents and discusses recent developments in the field. Basic configurations, a brief approach of the operating principle and recent applications are introduced for each interferometric architecture, making it easy to compare them and select the most appropriate one for the application at hand.

https://www.mdpi.com/2304-6732/8/7/265/pdf

In-Fiber Interferometric-Based Sensors: Overview and Recent Advances

Displacement measurements are of significant importance in a variety of critical scientific and engineering fields such as gravitational wave detection, geophysical research, and manufacturing industries. Due to the inherent advantages such as compactness, high sensitivity, and immunity to electromagnetic interference, in recent years, fiber optic sensors have been widely used in an expansive range of sensing applications, ranging from infra-structural health monitoring to chemical and biological sensing. Of particular interest here, fiber optic displacement sensors have gained wide interest and have evolved from basic intensity modulation-based configurations to more advanced structures, such as fiber Bragg grating-based, interferometric configurations, etc. This paper reviews specifically the advanced fiber optic displacement sensing techniques that have been developed in the past two decades. Details regarding the working principle, sensor design, and performance measures of fiber Bragg gratings-based, interferometers-based (including the Fabry-Perot interferometer, the Michelson interferometer, and the multimode interferometer), microwave photonics-based, and surface plasmon resonance-based fiber optic displacement sensors are given. Challenges and perspectives on future research in the development of practical and high-temperature tolerant displacement sensors are also discussed. 

Review of Fiber Optic Displacement Sensors

An in-line reflective dual-parameters fiber-optic sensor is proposed in this work, whereas it is experimentally verified by measuring both the liquid level and the local temperature distribution simultaneously. The proposed sensor configuration comprises a single-mode fiber (SMF), a tapered few-mode fiber (TFMF), as well as a silver-coated capillary tube. The extracted experimental results indicate that the liquid level only affects the power of the resonant dips, while having little impact on the wavelength. On the other hand, both the wavelength and the power of the resonant dips vary with the temperature change. Therefore, the simultaneous measurement of the liquid level and temperature can be realized according to the different responses of the resonant dips to the liquid level and temperature. The obtained liquid level and temperature sensitivities can reach the values of 0.106 dB/mm and 0.029 dB/°C, 35 pm/°C, respectively. The sensor exhibits the advantages of high stability and low cost, the demodulation relates on only one wavelength which can shorten the scanning wavelength range during measurement. The proposed sensor can be potentially applied where accurate and simultaneous measurements of both temperature and liquid level are required.

In-line reflected fiber sensor for simultaneous measurement of temperature and liquid level based on tapered few-mode fiber.

Displacement measurements are of significant importance in a variety of critical scientific and engineering fields, such as gravitational wave detection, geophysical research, and manufacturing industries. Due to the inherent advantages such as compactness, high sensitivity, and immunity to electromagnetic interference, in recent years, fiber optic sensors have been widely used in an expansive range of sensing applications, ranging from infrastructural health monitoring to chemical and biological sensing. Of particular interest here, fiber optic displacement sensors have gained wide interest and have evolved from basic intensity modulation-based configurations to more advanced structures, such as fiber Bragg grating (FBG)-based and interferometric configurations. This article reviews specifically the advanced fiber optic displacement sensing techniques that have been developed in the past two decades. Details regarding the working principle, sensor design, and performance measures of FBG-based, interferometers-based (including the Fabry–Perot interferometer, the Michelson interferometer, and the multimode interferometer), microwave photonics-based, and surface plasmon resonance-based fiber optic displacement sensors are given. Challenges and perspectives on future research in the development of practical and high-temperature tolerant displacement sensors are also discussed.

This manuscript experimentally validates a thin-film polymer and multimode fiber optic interaction-based low-cost optical fiber displacement sensor. The sensing setup is operated by deflecting a commercially Mylar Ⓡ polymer film using multimode optical fiber. The sensor exhibits a higher sensitivity of 24nm/ $\mu \text{m}$ and resolution of 41.6nm. The sensor’s analyses also demonstrate good polynomial approximation, with a maximal adjusted square of $\text {R}={0.9801}$ , and high stability, in which minimal power (0.4dB-Hour) and wavelength ( $0.05~\mu \text{m}/^{\circ }\text{C}$ ), and this parameter can be distinguished considering the wavelength shifting direction. The simplicity of the scheme, as well as the cost of the elements involved, make this technique a reliable alternative to detect micro-displacements.

Fiber Optic Fabry-Perot Micro-Displacement Sensor Based on Low-Cost Polymer Film

This manuscript presents the development of a low-pressure extrinsic Fabry-Perot fiber optic sensor based on a thin polyester film, using a phase signal analysis. The proposed interferometer is controlled by the simple contact interaction between the polymer membrane and a multimode fiber optic tip. The created cavity was uniformly stressed by applying a pressure varying from 0 to 2 psi. A finite element analysis was performed for these parameters. The stress applied to the membrane was below the yielding point. Thus, a linear study could be performed. The wavelength spectra exhibited a blue shift with a sensitivity of around 10.5 nm/psi. Although the interference spectra presented crosstalk measurements and required an initial set-point calibration, these effects were overcome by examining the spatial frequency components’ phase analysis. The sensors offered a high sensitivity, close to 3.5 rad/psi. Ultimately, this sensor is a high sensitivity and versatile alternative for low-pressure detection.

Low-pressure fiber-optic sensor by polyester Fabry-Perot cavity and its phase signal processing analysis

An experimental study of the interaction between a Mylar® polymer film and a multimode fiber-optic is presented for the simultaneous fiber-optic detection of low-pressure and liquid levels. The junction between the polymer and optical fiber produces an interference spectrum with maximal visibility and free spectral range around 9 dB and 31 nm, respectively. Water pressure, which is controlled by the liquid level, stresses the polymer. As a result, the spectrum wavelength shifts to the blue region, achieving high sensitivities around 2.49 nm/kPa and 24.5 nm/m. The polymeric membrane was analyzed using a finite element model; according to the results, the polymer shows linear stress response. Furthermore, the membrane material is operated below the yielding point. Moreover, the finite analysis provides information about the stress effect over the thickness and the birefringence changes. This sensor exhibits a quadratic polynomial fitting with an adjusted R-squared of 0.9539. The proposed sensing setup offers a cost-effective alternative for liquid level and low-pressure detection.

/pdf/low-pressure-and-liquid-level-fiber-optic-sensor-based-on-59hxsavrfb.pdf

M. Gutierrez-Rivera

Papers

Fiber Optic Fabry-Perot Micro-Displacement Sensor Based on Low-Cost Polymer Film

Low-pressure fiber-optic sensor by polyester Fabry-Perot cavity and its phase signal processing analysis

Low-pressure and liquid level fiber-optic sensor based on polymeric Fabry-Perot cavity.