Fiber Acoustic Sensor Research Articles

AE-IRMamba: Low-Complexity Inverted Residual Mamba for Identification of Piezoelectric Ceramic and Optical Fiber Acoustic Emission Sensors Signals

AE-IRMamba: Low-Complexity Inverted Residual Mamba for Identification of Piezoelectric Ceramic and Optical Fiber Acoustic Emission Sensors Signals

Ultra-thin DLC diaphragm-based optical fiber sensor achieving a highly sensitive and broadband acoustic response.

In the design of an extrinsic Fabry-Perot interferometer (EFPI) acoustic sensor, broadband response and high-sensitivity sensing are usually conflicting and need to be carefully balanced. Here, we present a novel, to the best of our knowledge, optical fiber acoustic sensor based on an ultra-thin diamond-like carbon (DLC) film, fabricated using the plasma-enhanced chemical vapor deposition method, and transferred by a surface-energy-assisted method. The sensor exhibits a broadband response ranging from 200 Hz to 100 kHz, maintains an average sensitivity of 457.3 mV/Pa within the range of 6 to 30 kHz, and can detect weak acoustic signals down to 3.23 µPa/Hz1/2@16.19 kHz. The combination of an ultra-thin DLC film with a relatively high Young's modulus and internal stresses results in a trade-off between high sensitivity and a broadband response. This performance demonstrates that our sensor is among the most advanced in the EFPI acoustic sensor family, with significant potential for applications such as photoacoustic spectroscopy, defect diagnosis, and bio-imaging.

Identification of Corrosion-Induced Optical Fiber Acoustic Emission Sensor Signals on the Bottom Plate of Oil Storage Tank Based on Multichannel Attention Mechanism (CBAM)

Identification of Corrosion-Induced Optical Fiber Acoustic Emission Sensor Signals on the Bottom Plate of Oil Storage Tank Based on Multichannel Attention Mechanism (CBAM)

Research on partial discharge detection based on distributed optical fiber acoustic sensor

Distributed acoustic sensors (DASs) have the advantage of long-distance and distributed monitoring of vibration signals. However, there are few studies on the application of DAS for partial discharge (PD) monitoring of power equipment. There is also a lack of related theoretical and methodological studies. In this paper, the DAS-measured phase signals are theoretically analyzed from the frequency and energy perspectives, and the method of PD broadband signal coverage using spectrum and energy accumulation is proposed. Fiber optic rings are employed for the detection of PD signals, and the precise localization of these signals is achieved by calculating the DAS energy spectrum. The fiber optic ring is wrapped around the cable joint to achieve the detection and locating of the PD signal. The results indicate that the use of a fiber optic ring can realize the sensitive detection and locating of PD. The signal strength is maximum when the length of the fiber ring is equal to the spatial resolution of DAS. The sensitivity of PD detection in cable joints can reach 40 pC, and the simultaneous detection and localization of PD at different locations can be realized. The research can provide support for theoretical and experimental for the monitoring of PD in power equipment.

Optical fiber acoustic sensor with gold diaphragm based Fabry-Perot interferometer

This work proposes an optical fiber acoustic sensor using a Fabry-Perot interferometer (FPI), which consists of an optical fiber end face and a gold diaphragm with an effective diameter of 75 µm and a thickness of 20 nm. The sensor has contrast of up to 34 dB and achieves audible acoustic signal sensing over a broad frequency response range from 70 Hz to 20 kHz with a linear response to sound pressure. The minimum detectable sound pressure is 815.5 μPa/Hz1/2 at 70 Hz. The sensor made of a pure gold diaphragm has stable performance and can work consistently over a long period, promising to be applied as an optical microphone for real-time communication in some extreme environments.

Application of pipeline leakage detection based on distributed optical fiber acoustic sensor system and convolutional neural network

Underwater pipelines are exposed to harsh environments, including high salinity, multi-modal vortex corrosion, and severe wave interference. Their safety is essential for the development and transportation of marine energy. Therefore, real-time safety monitoring of long-distance energy pipelines is of great strategic importance for ensuring the safety of life and property and energy security. With the rapid development of energy development, the corrosion and leakage mechanisms of natural gas pipelines, as well as their identification and early warning, have become the focus of attention. Optical fiber sensing technology has been applied to various energy safety monitoring fields. However, the mechanism of sound source fluctuations in pipeline leakage and the mutual coupling mechanism between distributed optical fiber sensing technology and leakage sound waves are not yet clear. This paper establishes a model based on sound wave propagation and leakage noise response, derives a quadratic fitting relationship between pipeline pressure fluctuations and leakage orifices and a relationship between leakage noise source standard deviation and orifices, and proposes a complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) permutation entropy underwater natural gas pipeline leakage signal recognition method based on distributed optical fiber acoustic sensing technology. The results of theoretical analysis are verified by experiments. It shows that the signal processing method of CEEMDAN permutation entropy is superior to traditional noise reduction methods, which can better preserve the features of the original signal; the radial basis function (RBF) neural network model can accurately identify four different leakage features with an accuracy of 88.15%, and its recognition stability and generalization ability are superior to convolutional neural network, backpropagation, and random forest. Therefore, the research results of this paper provide a new method for safety monitoring in the application of energy pipeline transportation engineering, and expand the potential application scenarios of distributed acoustic sensing sensor systems and RBF neural networks.

The Investigation of All-Sapphire Fabry–Perot Fiber Acoustic Sensor Operating Up to 800 °C

The Investigation of All-Sapphire Fabry–Perot Fiber Acoustic Sensor Operating Up to 800 °C

The Improved Wavelet Denoising Scheme Based on Robust Principal Component Analysis for Distributed Fiber Acoustic Sensor

The Improved Wavelet Denoising Scheme Based on Robust Principal Component Analysis for Distributed Fiber Acoustic Sensor

Compact optical fiber photoacoustic gas sensor with integrated multi-pass cell

Optical fiber acoustic sensors with miniature size and high sensitivity are attractive to develop compact photoacoustic spectroscopy. Here, a compact photoacoustic gas sensor was demonstrated by utilizing a diaphragm-based fiber-optic Fabry-Perot cavity as both the acoustic sensor and the multipass cell. A nanoscale graphite film was used as the flexible diaphragm to increase the acoustic sensitivity of the Fabry-Perot cavity and the cavity inner surface was coated with highly-reflective Au film to form a multipass cell for amplification of the photoacoustic signal. With a laser power of 20 mW at 1532.8 nm, the sensor demonstrated a low detection limit of ∼ 50 ppb for C2H2 gas with an integration time of ∼ 100 s. The optical fiber photoacoustic gas sensor with a millimeter-scale diameter and ppb-level detection limit is promising for trace gas sensing in various areas including industrial process and environmental monitoring.

Increasing the Signal-to-Noise Ratio in Underwater Distributed Optical Fiber Acoustic Sensor

Increasing the Signal-to-Noise Ratio in Underwater Distributed Optical Fiber Acoustic Sensor

Optimization of Photoacoustic Cell for Trace Acetylene Detection in Transformer Oil

This paper presents the development of a highly sensitive gas detection system based on a resonant photoacoustic cell for detecting dissolved gases in transformer oil. A simulation model of the resonant photoacoustic cell was studied and optimized the buffer chamber volume while ensuring signal enhancement. The volume of the photoacoustic cell was reduced by about 80% compared to the classical model. A resonant photoacoustic cell was then fabricated based on the optimized simulation optimization. The dual-resonance photoacoustic system was constructed by combining the resonant PA cell with a handmade cantilever fiber acoustic sensor. The system’s sensitivity was further improved by using an erbium-doped fiber amplifier, wavelength modulation, and harmonic detection technology. The experimental results showed that the system achieved a detection limit of 6 ppb and an excellent linear range under 1000 ppm for C2H2 gas. The developed gas detection system has potential applications for monitoring the condition of power transformers in power grids.

Investigation and performance improvement of optical fiber acoustic sensor based on diaphragm prestress tunable technology

In this paper, sensitivity and response frequency tunable optical fiber acoustic sensor technology is proposed for the first time, in which a C-shape pedestal mounted diaphragm sensor structure is employed for prestress tuning and consequently for the rigidity adjustment of the diaphragm to investigate and improve the performance of single mode-multimode-single mode (SMS) fiber acoustic sensor. By employing the proposed sensor structure, the influence of prestress on the resonance frequency and the sensitivity of optical fiber acoustic sensor can be investigated theoretically and experimentally. The results also confirm that the proposed method provide a simple but effective solution for the performance improvement of acoustic sensor, by which the response range can be extended from 800 Hz to 1500 Hz with a sensitivity fluctuation of 0.7 dB and a value of 0.998 by adjusting the prestress of diaphragm, meanwhile the background noise can be significantly suppressed from −57 dB to −67 dB.

Airborne Sound Sensing System Based on DAS and Ultra-Simple Transducer Structure

Fiber-distributed optical fiber acoustic sensor (DAS) is generally used in distributed long-distance acoustic/vibration measurement. Recently, DAS is also used in weak airborne sound detection. To improve the sensitivity of DAS, using a state-of-the-art acoustic transducer or a special enhanced scattering fiber, which are uncommon in the industrial site, is often essential, according to the previous research. In this work, the fading of DAS is suppressed by the multi-frequency probes and polarization-diversity-receiver scheme. The self-noise of DAS is further lowered by the phase averaging of multiple acoustic channels wound on the transducer. We found that, supported by this high-performance DAS, even if the transducer is made with an ultra-simple plastic structure in daily life, the system can achieve high-sensitivity airborne sound sensing. The proposed simple acoustic transducer can reach the sensitivity level of −106.5 dB re. 1 rad/μPa at a sensing range of 5.1 km, which can meet many demands on the industrial site.

A preliminary study on wellbore flow interpretation of fiber optic vibration signals based on K-means clustering algorithm

The wellbore flow analysis of optical fiber vibration signal depends on distributed optical fiber logging. Distributed optical fiber logging technology identifies the fluid in the well through distributed optical fiber acoustic sensor (DAS) and distributed optical fiber temperature sensor (DTS). Distributed optical fiber sensor has the advantages of small underground interference, high efficiency and low cost. In this paper, the wellhead data extracted by the distributed optical fiber acoustic sensor is used to calculate the upper bound of the fluid sound frequency band in the pipe by nonlinear least squares fitting. The K-means clustering algorithm is used to cluster the optical fiber vibration signals in the low frequency band. According to the clustering results, the ratio of the optical fiber signal eigenvalues of each production layers is obtained, and the trend of the ratio of the optical fiber signal eigenvalues of each production layers is judged to be close to the trend of the water absorption intensity. Compared with traditional acoustic logging, the wellbore flow analysis using distributed optical fiber acoustic sensor can quickly determine the production contribution of each layer and the change of fluid phase state in the production cycle. Combined with traditional production logging technology, distributed optical fiber logging shows its reliability and accuracy in data collection, logging interpretation and production application. Starting from the principle of distributed optical fiber acoustic sensing technology, this paper briefly expounds the properties of distributed optical fiber acoustic sensor and the principle of injection profile logging, systematically introduces the processing of distributed optical fiber acoustic data, and emphatically introduces the accuracy of K-means clustering algorithm for analyzing distributed optical fiber acoustic signal and qualitative judgment of production layer, which provides a new idea for judging the accuracy of production layers.

High noise immunity phase generated carrier demodulation technology for the modulation depth influence elimination

In the traditional phase generated carrier (PGC) demodulation algorithms, the modulation depth is an important factor affecting the demodulation effect, and the demodulated signal can be distorted with the modulation depth variation. To address this limitation, this study proposes a method that introduces the differential self-division operation in the traditional PGC-Arctan algorithm framework to eliminate the influence of the modulation depth of distributed optical fiber acoustic sensor system. The simulation results of signal demodulation at different modulation depths and different SNR values show that the proposed algorithm can eliminate adverse effects of the modulation depth and achieve good demodulation performance. An experimental platform is built to verify the simulation results further. Experimental results show that under different modulation depths, the amplitude error of the proposed algorithm is 0.105%, and the total harmonic distortion is 0.068%. Furthermore, the dynamic range of the proposed algorithm is up to 62.5 dB. The comprehensive analysis results verify that the proposed algorithm can effectively eliminate the modulation depth influence, indicating its good stability and noise resistance. Therefore, the proposed algorithm has a good application prospect in high-performance optical fiber acoustic sensing systems.

Real-Time Self-Calibrating Phase-Shifted Demodulation Method Based on Polarized Low-Coherence Interference for Optical Fiber Acoustic Sensor

A real-time self-calibrating quadrature phase-shift demodulation method for external Fabry–Perot interferometric (EFPI) sensors is proposed and demonstrated. Two birefringent crystal blocks with matching lengths are used to generate two orthogonal interference signals, and the third rotating birefringent crystal block is used as a compensation path for real-time normalization of two orthogonal interference signals. The signals are finally processed by the differential cross multiplication (DCM) algorithm demodulation. Experimental results show that the demodulation scheme can not only correctly demodulate low-frequency dynamic signals but also demodulate ultrasonic signals with high stability and high speed, and has a signal-to-noise ratio (SNR) of up to 90 dB. When the sensor cavity length drifts between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 4.94\,\,\mu \text{m}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.584 ~\mu \text{m}$ </tex-math></inline-formula> , it still has stable demodulation performance and is suitable for EFPI sensors with different diaphragms. The demodulation scheme provides a simple, effective, high-speed, and robust solution for dynamic signal measurement in complex environments based on real-time self-calibrating, which demonstrates great potential in practical engineering applications.

Fabry-Perot Interference Fiber Acoustic Wave Sensor Based on Laser Welding All-Silica Glass

Due to the small difference between the thermal expansion coefficients of silica optical fiber and silica glass, they are used as probe materials of optical fiber acoustic wave sensors. According to the light absorption characteristics of a pressure-sensitive silica diaphragm and silica glass, the laser welding of an all-silica Fabry–Perot (FP) interference optical fiber acoustic wave sensor with a CO2 laser is proposed. For understanding the influence of thermal expansion of sealing air in an FP cavity and the drift of interference-intensity demodulation working point of a FP interference acoustic wave sensor, we designed a process for the laser welding of an ultra-thin silica diaphragm and sleeve and optical fiber and sleeve. The exhaust hole of the FP cavity is reserved in the preparation process, and an amplified spontaneous emission light source and a tunable optical-fiber FP filter are introduced to stabilize the working point. The sensor is tested with a 40 kHz sound vibration signal. The results show that the sound pressure sensitivity of the sensor to an acoustic source of 0.02–0.1 W/cm2 is 6.59 mV/kPa. The linearity coefficient is 0.99975, indicating good linearity.

Polarization fading mitigation in distributed acoustic sensors based on a high-speed polarization rotator.

A distributed optical fiber acoustic sensor based on interferometric demodulation technique with no polarization fading is demonstrated. A polarization diversity scheme based on a high-speed polarization rotator is used to eliminate signal fading due to polarization mismatch in the Rayleigh backscattered signal between adjacent points on the sensing fiber. This technique yields a spatially uniform response to the applied strain. The sensor exhibited spatial and strain resolutions of <4 m and <7 nɛ, respectively.

Environment-Robust Polarization-Based Phase-Shift Dynamic Demodulation Method for Optical Fiber Acoustic Sensor

In this paper, an environment-robust polarization-based phase-shift dynamic demodulation method for optical fiber acoustic sensor is proposed. Through optical lever effect of polarization low-coherence interference and amplitude scaling differential cross multiplication (AS-DCM) algorithm, acoustic-source induced interference phase of the acoustic sensor can be demodulated in real-time with high precision. The maximum relative phase demodulation error was only 0.694% when the cavity length had an offset ∼4 μm. The maximum cavity length demodulation error was keeping less than 3.988 nm under the optical power reduced ten times, which demonstrated an ultra-stable demodulation for the largest permitted optical power attenuation range, to our best knowledge. The proposed method has a capability of tolerating large optical power attenuation and large cavity length random offset, providing an environment-robust way for optical fiber acoustic sensor working in extreme environments.

Fiber Acoustic Sensor With Stable Operating-Point Based on a Photo-Thermal Cavity

Ambient temperature fluctuations inevitably affect the stability and accuracy of most of the existing fiber acoustic sensors. To overcome this drawback, a fiber acoustic wave transducer with stable operating-point based on a photo-thermal cavity (PTC) is proposed in this article. The proposed Fabry-Perot interferometer (FPI) is formed by splicing a section of high-attenuation microfiber (HAMF) between a pair of wavelength-matched fiber Bragg gratings (FBGs). The applied acoustic wave would dynamically disturb the medium refractive index (RI) around the HAMF, causing the narrow Fabry-Perot interferometric fringe shift. The wavelength of the probe laser is tuned on the slope of the interferometric fringe. Theoretical analysis and experimental verification had been performed. The HAMF acts as an excellent active compensated component, which can steady the operating-point through adjusting the heating light source power. The proposed sensor structure has a compact size, simple fabrication and especially the stable operating-point, which make it more suitable for in-situ detecting in application of bioimaging or underwater sonar.