High Sensitivity and High Stability Dual Fabry-Perot Interferometric Fiber-Optic Acoustic Sensor Based on Sandwich-Structure Composite Diaphragm

Abstract

A dual Fabry-Perot (FP) interferometric fiber-optic acoustic sensor based on sandwich-structure composite diaphragm is proposed, where fixed phase difference is generated by two FP interferometers (FPIs) with different cavity length. An ellipse fitting differential cross multiplication (EF-DCM) interrogation process is applied for phase demodulation to overcome drawbacks of quadrature point based intensity demodulation, such as temperature drifting, optical power jitter and limited dynamic range. Besides, benefiting from the large area sandwich-structure composite diaphragm, high sensitivity and wide flat frequency response are obtained. Experimental results show that phase sensitivity is-121.11 dB re 1 rad/μPa@250 Hz and sensitivity fluctuation is below 0.8 dB between 2-250Hz. To prove the high stability of the demodulation system, acoustic signal test is performed at different wavelength and different optical power and a fluctuation below 3% is observed. Moreover, profiting from the dual FP sensor structure, the acoustic sensor is get rid of influence of temperature drifting which usually leads to variation of cavity length of fiber optic acoustic sensor. The proposed sensor structure also overcomes drawbacks of traditional dual wavelength demodulation such as extra noise introduced by erbium doped fiber amplifier (EDFA) and high cost.

Acoustic Performance Study of Fiber-Optic Acoustic Sensors Based on Fabry–Pérot Etalons with Different Q Factors

“…For instance, while large-sized piezoelectric acoustic sensors possess a high sensitivity and signal-to-noise ratio, it is disadvantageous to sensor miniaturization that is urgently desired in practical applications, and the low resonant frequency of membranes result in a narrow frequency response of sensors. Furthermore, in order to adapt to the expansion of the acoustic detection field and the application requirements of the harsh environment, fiber-optic acoustic sensors (FOASs) with the advantages of a high sensitivity [6][7][8][9], immunity to electromagnetic interference [10][11][12], high temperature resistance and miniaturization [13,14] have been widely studied and applied in the fields of national defense security [15,16], medical diagnosis [17][18][19] and non-destructive testing [20,21]. At present, optical fiber [8] and membrane [22][23][24][25][26] are the most commonly used sound-sensitive element.…”

A Realization of Stabilizing the Output Light Power from a Laser Diode: A Practical Approach

“…Authors in [2] proposed an optical scanning system wherein they suggested changing the intensity distribution from the center and the edge of the beam using a prism. Authors in [3] used a double Fabry Perot interferometer acoustic sensor to get rid of temperature drifting. Authors in [4] tried a number of alterations using silicone converters which helped increase the top-limit excitation power ranging from 60 to 180Wcm.…”

Research on the Frequency Response and Dynamic Range of the Quadrature Fiber Optic Fabry–Perot Cavity Microphone Based on the Differential Cross Multiplication Demodulation Algorithm

“…1. Quadrature signal acquisition: The methods to obtain two quadrature signals mainly include the phase generated carrier (PGC) method [19][20][21][22], multiwavelength method [23][24][25], construction of quadrature F-P cavity method [26][27][28][29], etc. The PGC method is susceptible to the effects of external factors such as drift of mixing signal amplitude and change of phase modulation amplitude.…”

“…In addition, the traditional PGC method is not suitable for short cavity interferometers, as with most monochromatic sources it is not possible to provide sufficient modulation depth due to the structural characteristics of short cavity interferometers. The multiwavelength approach requires optical filters or multiple light sources of different wavelengths, which complicates the sensing system and prevents the detection of high frequency signals due to the limitations of the spectrometer scanning speed [28]. In contrast, the method to obtain the quadrature signals by constructing a quadrature F-P cavity structure is simple, easy, and inexpensive.…”

“…However, there are quite limited systematic studies on their key performance. The current research is concerned with the stability of the quadrature fiber optic Fabry-Perot cavity microphone (Q-FFPM) solution and the optimisation of the diaphragm structure and materials, but there is no complete analysis of the corresponding frequency range and dynamic range [28,34,35]. In this paper, the frequency response and dynamic range of Q-FFPM-DCM are studied systematically using simulation and analysis methods.…”