Among fiber optic acoustic sensors, Fabry-Perot sensors have attracted increasing research attention due to their high sensitivity, simple structure, and ease of preparation. The vibrating diaphragm of Fabry-Perot sensors is the key to achieve high performance. Compared to traditional diaphragms based on metal or polymer, 2D materials with the features of high Young's modulus and ultra-thinness are ideal diaphragm materials for significantly enhancing the acoustic sensitivity and broadening frequency range of the sensors. In this work, graphene oxide is used as the vibrating diaphragm due to the water solubility and the ease of thin-film preparation. In order to improve the stability of the system, we have developed a phase demodulation method using three orthogonal signals. The three-path phase-shifting algorithm can eliminate the effect of DC offset from the unstable optical signal. Our graphene oxide-based Fabry-Perot acoustic sensor can test and demodulate the vibration signal in real-time, demonstrating long-term stability and insensitivity to changes in light intensity.
Phase interrogation method can effectively avoid the operational spacing problems of fiber-optic Fabry-Perot (F-P)sensors. Based on the principles of F-P interference and low coherence interference, polarizers and birefringent crystals are applied to construct signals with quadrature relationship. A four-quadrant inverse tangent operation is employed to accurately calculate the phase values. We have performed rapid, high-speed measurements of dynamic pressure with aF-P sensor. Experimental results show that the method can achieve real-time pressure measurements up to 3 MPa with an interrogation rate of 5 kHz. This research holds much promise for the promotion of interferometric based fiber-optic sensors and applications of pressure measurements.
Indium tin oxide (In2O3-SnO2-90/10 wt%, ITO) is a semiconductor material with excellent electrical conductivity. In this paper, ITO was deposited on a multimode optical fiber by magnetron sputtering technique and characterized by using Scanning Electron Microscopy (SEM). It is subsequently used as a working electrode in a three-electrode system to study its electrochemical behavior in different solutions. In 0.1 M KCl containing such redox probes as 1 mMofK3[Fe(CN)6] were discussed by Cyclic voltammetry (CV) method at different scan rates. The observed electrochemical processes are quasi-reversible and diffusion-controlled. The results of the investigation inject new vitality to enhance the intersection of electrochemistry and optics disciplines, and also lay the foundation for dual-domain determination.
In this paper, a whisker array sensor for object surface shape measurement is designed and experimentally demonstrated. The developed sensor is based on a 4×4 whisker array with fiber Bragg grating, which imitates the structure of the facial whiskers of animals like mice and dogs. The surface shape reconstruction is based on the curvature information of each sensing point by measuring the wavelength shift of each fiber Bragg grating fixed on the whisker. The conversion coefficient between wavelength shift and bending curvature is obtained then the change of fiber Bragg grating is converted into corresponding bending curvature. The measurement error on the altitude of the whisker of each sensing point is about 1.2%. By curve fitting the curvature information of the whole fiber Bragg grating whisker array, the surface shape of the target surface is reconstructed. In this experiment, the spatial resolution of the sensor is 10 mm, which can theoretically meet the need of any spatial resolution by adjusting the measurement algorithm. The design successfully realizes surface shape sensing, which has important practical value in the field of robot tactile, in aviation and disaster relief.
The orthogonal phase demodulation method can effectively avoid the problem of the working interval of the optical fiber Fabry-Perot (F-P) sensor and has high accuracy. Based on the principle of the low-coherence interference, polarizers and birefringent crystals are used to construct signals with orthogonal relationships in the orthogonal phase demodulation system. Four-quadrant inverse tangent operation is used to accurately calculate the phase value. In order to verify the frequency band response of the demodulation system, the acoustic signals of frequencies in the range of 200 Hz-25 kHz are interrogated. Experimental results show that the orthogonal phase demodulation system can be appled to demodulate the signals of wide frequency band. The research has value for the promotion and application of orthogonal phase demodulation system based on birefringent crystals and polarization technology
A metal diaphragm-based airflow sensor based on fiber-optic Fabry-Perot (F-P) interference has been proposed and experimentally demonstrated. The sensor is composed of glass sleeving, ceramic ferrule and metal diaphragm. Through data calibration, a practical airflow sensor has been fabricated. As a result of the stainless steel diaphragm and open F-P cavity, the durability of the sensor is ensured, and it can be used in poor air quality environments. Experimental results in the airflow field show that the sensor has the potential to estimate the air quantity of high-speed airflow in various air conduit
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