Encapsulated Microbubble Fiber-tip Fabry-Perot Cavity with Tunable Bandwidth for Sensitive Acoustic Detection

The optical acoustic detection system based on the Fabry Pérot Etalon (FPE) with high quality–factor (High Q) and stability structure is described and tested. The FPE contains two high–reflectivity Plano–Concave lenses, achieving high fineness and stability. The protective structure of the confocal stabilized FPE is composed of an invar tube, copper sheath, Bakelite sheath and aluminum housing to protect the sensor from the effects of ambient temperature and vibration. The audio signal is injected into the cavity through the sound hole located in the center of the cavity. Acoustic waves induce the vibration of the medium in the cavity, which leads to a simultaneous change in the FPE optical path and a shift of the interference spectrum. The acoustic detection system is built, and the frequency of the laser is locked on the resonant frequency points of the FPE by using phase modulation technology, so as to detect acoustic signals of different frequencies and amplitudes. In addition, the sensitivity of the proposed sensor exceeds 34.49 mV/Pa in the range of 20 Hz–20 kHz. A Signal-to-Noise Ratio (SNR) of 37 dB can be achieved at 20 Hz. Acoustic signal detection technology based on the FPE stability model is used to test the theoretical feasibility of the future high sensitivity Fabry Pérot Interferometric (FPI) acoustic sensors.

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Fibre Fabry-Perot sensor for acoustic detection

10.1117/12.786071 ◽

2008 ◽

Cited By ~ 2

Author(s):

S. E. U. Lima ◽

O. Frazão ◽

F. M. Araújo ◽

L. A. Ferreira ◽

V. Miranda ◽

...

Keyword(s):

Acoustic Detection ◽

Fabry Perot

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

Micromachines ◽

10.3390/mi13010118 ◽

2022 ◽

Vol 13 (1) ◽

pp. 118

Author(s):

Jiamin Chen ◽

Chenyang Xue ◽

Yongqiu Zheng ◽

Jiandong Bai ◽

Xinyu Zhao ◽

...

Keyword(s):

Sound Pressure ◽

Fiber Optic ◽

Dynamic Range ◽

Q Factor ◽

Acoustic Detection ◽

Performance Study ◽

Application Range ◽

Acoustic Performance ◽

Fabry Perot ◽

Q Factors

The ideal development direction of the fiber-optic acoustic sensor (FOAS) is toward broadband, a high sensitivity and a large dynamic range. In order to further promote the acoustic detection potential of the Fabry–Pérot etalon (FPE)-based FOAS, it is of great significance to study the acoustic performance of the FOAS with the quality (Q) factor of FPE as the research objective. This is because the Q factor represents the storage capability and loss characteristic of the FPE. The three FOASs with different Q factors all achieve a broadband response from 20 Hz to 70 kHz with a flatness of ±2 dB, which is consistent with the theory that the frequency response of the FOAS is not affected by the Q factor. Moreover, the sensitivity of the FOAS is proportional to the Q factor. When the Q factor is 1.04×106, the sensitivity of the FOAS is as high as 526.8 mV/Pa. Meanwhile, the minimum detectable sound pressure of 347.33 μPa/Hz1/2 is achieved. Furthermore, with a Q factor of 0.27×106, the maximum detectable sound pressure and dynamic range are 152.32 dB and 107.2 dB, respectively, which is greatly improved compared with two other FOASs. Separately, the FOASs with different Q factors exhibit an excellent acoustic performance in weak sound detection and high sound pressure detection. Therefore, different acoustic detection requirements can be met by selecting the appropriate Q factor, which further broadens the application range and detection potential of FOASs.

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Response Bandwidth Design of Fabry-Perot Sensors for Partial Discharge Detection Based on Frequency Analysis

Journal of Sensors ◽

10.1155/2019/1026934 ◽

2019 ◽

Vol 2019 ◽

pp. 1-11 ◽

Cited By ~ 1

Author(s):

Qi-Chao Chen ◽

Wei-Chao Zhang ◽

Hong Zhao

Keyword(s):

Acoustic Emissions ◽

Experimental System ◽

Acoustic Signals ◽

Partial Discharges ◽

Acoustic Detection ◽

Design Standards ◽

Fiber Sensors ◽

Response Bandwidth ◽

Fabry Perot ◽

Higher Sensitivity

The insulation of power equipment can be effectively assessed by analyzing the acoustic signals originated from partial discharges (PD). Fabry-Perot (F-P) sensors are capable of detecting PD acoustic signals. Although the frequency bandwidth of an F-P sensor is mainly referred to conventional piezoelectric transducer (PZT) sensor, it is still doubtful to identify a suitable bandwidth for fiber sensors in detection of PD signals. To achieve a suitable bandwidth for an F-P sensor, the frequency distribution of PD acoustic emission is investigated, and an extrinsic F-P sensor is designed to detect acoustic signals generated from PD. F-P sensors with different intrinsic frequencies are fabricated as possible design standards of bandwidth for acoustic detection. PD acoustic signals are detected by these F-P sensors and PZT sensors in the experimental system, in which four typical electrode models are employed. The measured results of frequency performance are analyzed in linear and semilogarithmic coordinates. The results show that F-P sensors can effectively detect PD acoustic emissions in both wideband and narrowband modes. Moreover, F-P sensors achieve a higher sensitivity in the narrowband mode. We propose that intrinsic frequency of the F-P sensor should be designed in the frequency range of 100–170 kHz to obtain maximum sensitivity.

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