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14 pages, 4846 KB

Open AccessArticle

In-Fiber Hybrid Structure Sensor Based on the Vernier Effect for Vector Curvature and Temperature Measurement

by Sunde Wang, Tiantong Zhao, Baoqun Li, Silun Du, Deqi Li, Dongmei Liu and Tianshu Wang

Photonics 2024, 11(8), 703; https://doi.org/10.3390/photonics11080703 - 28 Jul 2024

Cited by 3 | Viewed by 1605

A vector curvature and temperature sensor based on an in-fiber hybrid microstructure is proposed and experimentally demonstrated. The proposed scheme enables the dimensions of the Fabry–Perot and Mach–Zehnder hybrid interferometer to be adjusted for the formation of the Vernier effect by simply changing the length of a single optical fiber. The sensor is fabricated using a fiber Bragg grating (FBG), multimode fiber (MMF), and a single-hole dual-core fiber (SHDCF). The sensor exhibits different curvature sensitivities in four vertical directions, enabling two-dimensional curvature sensing. The temperature and curvature sensitivities of the sensor were enhanced to 100 pm/°C and −25.55 nm/m⁻¹, respectively, and the temperature crosstalk was minimal at −3.9 × 10⁻³ m⁻¹/°C. This hybrid microstructure sensor technology can be applied to high-sensitivity two-dimensional vector curvature and temperature detection for structural health monitoring of buildings, bridge engineering, and other related fields. Full article

(This article belongs to the Section Lasers, Light Sources and Sensors)

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13 pages, 3265 KB

Open AccessArticle

Fabry–Perot Cavity Optimization for Absolute Strain Sensing Using Finite Element Analysis

by João M. B. Pereira, Paula M. P. Gouvea, Arthur M. B. Braga, Isabel C. S. Carvalho and Antonio C. Bruno

Sensors 2023, 23(21), 8785; https://doi.org/10.3390/s23218785 - 28 Oct 2023

Cited by 5 | Viewed by 2037

Abstract

The finite element method (FEM) was used to investigate the optical–mechanical behavior of a Fabry–Perot Interferometer (FPI) composed of a capillary segment spliced between two sections of standard optical fiber. The developed FEM model was validated by comparing it with theory and with previously published experimental data. The model was then used to show that the absolute strain on the host substrate is usually smaller than the strain measurement obtained with the sensor. Finally, the FEM model was used to propose a cavity geometry that can be produced with repeatability and that yields the correct absolute strain experienced by the host substrate, without requiring previous strain calibration. Full article

(This article belongs to the Special Issue Distributed and Single-Point Fiber Optic Sensors: Applications and Technology)

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12 pages, 4769 KB

Open AccessArticle

Compact Harmonic Vernier Sensor Based on an In-Fiber FPI with Three Reflector System for Simultaneous Gas Pressure and Temperature Measurement

by Jinxiao Dan, Wenjie Dang, Zeren Li, Pengyu Nan, Guoguo Xin, Kok-Sing Lim, Harith Ahmad and Hangzhou Yang

Sensors 2023, 23(8), 4142; https://doi.org/10.3390/s23084142 - 20 Apr 2023

Cited by 10 | Viewed by 2557

Abstract

In this work, we proposed a sensitivity-enhanced temperature sensor, a compact harmonic Vernier sensor based on an in-fiber Fabry–Perot Interferometer (FPI), with three reflective interfaces for the measurement of gas temperature and pressure. FPI consists of air and silica cavities formulated by single-mode optical fiber (SMF) and several short hollow core fiber segments. One of the cavity lengths is deliberately made larger to excite several harmonics of the Vernier effect that have different sensitivity magnifications to the gas pressure and temperature. The spectral curve could be demodulated using a digital bandpass filter to extract the interference spectrum according to the spatial frequencies of resonance cavities. The findings indicate that the material and structural properties of the resonance cavities have an impact on the respective temperature sensitivity and pressure sensitivity. The measured pressure sensitivity and temperature sensitivity of the proposed sensor are 114 nm/MPa and 176 pm/°C, respectively. Therefore, the proposed sensor combines ease of fabrication and high sensitivity, making it great potential for practical sensing measurements. Full article

(This article belongs to the Section Environmental Sensing)

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12 pages, 5274 KB

Open AccessArticle

Distributed Acoustic Sensing Based on Coherent Microwave Photonics Interferometry

by Liwei Hua, Xuran Zhu, Baokai Cheng, Yang Song, Qi Zhang, Yongji Wu, Lawrence C. Murdoch, Erin R. Dauson, Carly M. Donahue and Hai Xiao

Sensors 2021, 21(20), 6784; https://doi.org/10.3390/s21206784 - 13 Oct 2021

Cited by 9 | Viewed by 4553

Abstract

A microwave photonics method has been developed for measuring distributed acoustic signals. This method uses microwave-modulated low coherence light as a probe to interrogate distributed in-fiber interferometers, which are used to measure acoustic-induced strain. By sweeping the microwave frequency at a constant rate, the acoustic signals are encoded into the complex microwave spectrum. The microwave spectrum is transformed into the joint time–frequency domain and further processed to obtain the distributed acoustic signals. The method is first evaluated using an intrinsic Fabry Perot interferometer (IFPI). Acoustic signals of frequency up to 15.6 kHz were detected. The method was further demonstrated using an array of in-fiber weak reflectors and an external Michelson interferometer. Two piezoceramic cylinders (PCCs) driven at frequencies of 1700 Hz and 3430 Hz were used as acoustic sources. The experiment results show that the sensing system can locate multiple acoustic sources. The system resolves 20 nε when the spatial resolution is 5 cm. The recovered acoustic signals match the excitation signals in frequency, amplitude, and phase, indicating an excellent potential for distributed acoustic sensing (DAS). Full article

(This article belongs to the Special Issue Fiber Optic Sensors for Biological, Chemical, Acoustic, and Magnetic Field Sensing)

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12 pages, 5118 KB

Open AccessArticle

In-Fiber Collimator-Based Fabry-Perot Interferometer with Enhanced Vibration Sensitivity

by Bin Du, Xizhen Xu, Jun He, Kuikui Guo, Wei Huang, Fengchan Zhang, Min Zhang and Yiping Wang

Sensors 2019, 19(2), 435; https://doi.org/10.3390/s19020435 - 21 Jan 2019

Cited by 29 | Viewed by 7895

Abstract

A simple vibration sensor is proposed and demonstrated based on an optical fiber Fabry-Perot interferometer (FPI) with an in-fiber collimator. The device was fabricated by splicing a quarter-pitch graded index fiber (GIF) with a section of a hollow-core fiber (HCF) interposed between single mode fibers (SMFs). The static displacement sensitivity of the FPI with an in-fiber collimator was 5.17 × 10⁻⁴ μm⁻¹, whereas the maximum static displacement sensitivity of the device without collimator was 1.73 × 10⁻⁴ μm⁻¹. Moreover, the vibration sensitivity of the FPI with the collimator was 60.22 mV/g at 100 Hz, which was significantly higher than the sensitivity of the FPI without collimator (11.09 mV/g at 100 Hz). The proposed FPI with an in-fiber collimator also exhibited a vibration sensitivity nearly one order of magnitude higher than the device without the collimator at frequencies ranging from 40 to 200 Hz. This low-cost FPI sensor is highly-sensitive, robust and easy to fabricate. It could potentially be used for vibration monitoring in remote and harsh environments. Full article

(This article belongs to the Special Issue Cantilever Sensor)

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14 pages, 4052 KB

Open AccessReview

A Review of Recent Results on Simultaneous Interrogation of Multiple Fiber Bragg Grating-Based Sensors Using Microwave Photonics

by Lawrence R. Chen, Maria-Iulia Comanici, Parisa Moslemi, Jingjing Hu and Peter Kung

Appl. Sci. 2019, 9(2), 298; https://doi.org/10.3390/app9020298 - 15 Jan 2019

Cited by 18 | Viewed by 4641

Abstract

We review recent results on exploiting microwave photonics to enable simultaneous interrogation of multiple fiber Bragg grating (FBG)-based sensors. In particular, we describe the use of (1) microwave photonic filtering and (2) chirped microwave pulse generation and compression as a means to map the wavelength (spectral) changes in the response of FBG-based sensors (specifically, an in-fiber Fabry-Pérot cavity sensor based on FBGs, FBG sensors directly, and a linearly chirped FBG sensor) to applied temperature (or strain) to the power of a radio-frequency signal (i.e., a wavelength-to-power mapping) or to the correlation peak of the compressed microwave signal. The approaches support high-resolution and high-speed interrogation and can be suitable for large scale sensing networks. Full article

(This article belongs to the Special Issue Microwave Photonics 2018)

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12 pages, 5129 KB

Open AccessArticle

Optimal Design of an Hourglass in-Fiber Air Fabry-Perot Microcavity—Towards Spectral Characteristics and Strain Sensing Technology

by Qi Wang, Dongchao Yan, Binbin Cui and Zixuan Guo

Sensors 2017, 17(6), 1282; https://doi.org/10.3390/s17061282 - 4 Jun 2017

Cited by 4 | Viewed by 5653

Abstract

An hourglass in-fiber air microcavity Fabry-Perot interferometer is proposed in this paper, and its second reflecting surface of in-fiber microcavity is designed to be a concave reflector with the best curvature radius in order to improve the spectral characteristics. Experimental results proved that the extinction ratio of Fabry-Perot interferometer with cavity length of 60 μm and concave reflector radius of 60 μm is higher than for a rectangular Fabry-Perot interferometer with cavity length of 60 μm (14 dB: 11 dB). Theory and numerical simulation results show that the strain sensitivity of sensor can be improved by reducing the microcavity wall thickness and microcavity diameter, and when the in-fiber microcavity length is 40 μm, the microcavity wall thickness is 10 μm, the microcavity diameter is 20 μm, and the curvature radius of reflective surface II is 50 μm, the interference fringe contrast of is greater than 0.97, an Axial-pull sensitivity of 20.46 nm/N and resolution of 1 mN can be achieved in the range of 0–1 N axial tension. The results show that the performance of hourglass in-fiber microcavity interferometer is far superior to that of the traditional Fabry-Perot interferometer. Full article

(This article belongs to the Section Physical Sensors)

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