Fiber-optic Vibration Sensor Research Articles

Low frequency vibration monitoring of wind turbine tower based on optical fiber sensor and its potential for internet of things

Among all renewable energy sources, wind energy is a cost-effective alternative energy source. The majority of wind turbines are built in harsh environments due to their power generation characteristics, which is one of the prime reasons resulting in frequent failures of wind turbine. Among various failures, the vibration of wind turbine tower cannot be ignored because it is a precursor of the failure of the wind turbine. The electrical vibration sensors have the problems of power supply and electromagnetic interference for the condition assessment of wind turbine tower. A vibration sensor based on optical Fabry-Perot (F-P) interference principle with high sensitivity is designed, fabricated and characterized to further meet the requirements of vibration detection of wind turbine tower. The mechanical simulation model of the diaphragm and optical vibration platform is constructed to verify the sensing characteristic of the F-P optical fiber vibration sensor (OFVS). The experiment results indicate a resonant frequency of the F-P OFVS of 223 Hz, an output sensitivity of 122.22 mV/m·s−2 at 10 Hz, and a horizontal output of less than 6 %. In addition, the designed F-P OFVS possesses the superiorities of compact structure, passive and excellent anti-electromagnetic interference, and has a wide application prospect in the vibration detection of the wind turbine tower.

Modeling of fiber-optic vibration sensor based on attached bragg grating

The article presents a numerical analysis of the possibility of creating a fiber-optic vibration sensor based on an attached Bragg grating. The sensor consists of two inert masses connected to each other by several membranes and an optical fiber with a fiber Bragg grating (FBG). The study is divided into two main stages: modeling the mechanical part of the sensor, assessing cross-influence and the influence of external temperatures, and developing a signal processing algorithm. A mechanical study of the vibration sensor was conducted to determine its resonant frequency and to determine the optimal length of the elastic beam. The optical part of the study focused on selectingoptimal parameters for the configuration of the arrangement of optical fibers. The results showed that the sensor has its own oscillation frequency above 2000 Hz, and there is a weak dependence of the sensor's sensitivity on the frequency of oscillations with a beam length of 1 mm. The research contributes to the development of fiber-optic accelerometers for measuring and analyzing vibration in various application areas.

Temperature-Decoupled Single-Crystal MgO Fiber-Optic Fabry-Perot Vibration Sensor Based on MEMS Technology for Harsh Environments.

A high-temperature-resistance single-crystal magnesium oxide (MgO) extrinsic Fabry-Perot (FP) interferometer (EFPI) fiber-optic vibration sensor is proposed and experimentally demonstrated at 1000 °C. Due to the excellent thermal properties (melting point > 2800 °C) and optical properties (transmittance ≥ 90%), MgO is chosen as the ideal material to be placed in the high-temperature testing area. The combination of wet chemical etching and direct bonding is used to construct an all-MgO sensor head, which is favorable to reduce the temperature gradient inside the sensor structure and avoid sensor failure. A temperature decoupling method is proposed to eliminate the cross-sensitivity between temperature and vibration, improving the accuracy of vibration detection. The experimental results show that the sensor is stable at 20-1000 °C and 2-20 g, with a sensitivity of 0.0073 rad (20 °C). The maximum nonlinearity error of the vibration sensor measurement after temperature decoupling is 1.17%. The sensor with a high temperature resistance and outstanding dynamic performance has the potential for applications in testing aero-engines and gas turbine engines.

Efficient On-Demand Design of Fiber Optic Vibration Sensor With a Symmetric Bidirectional Neural Network

Efficient On-Demand Design of Fiber Optic Vibration Sensor With a Symmetric Bidirectional Neural Network

Fiber optic vibration sensor for applications in the field of ground vibrations

We have proposed a vibration sensor based on a Michelson interferometer. The sensor was developed in the form of a triaxial accelerometer, calibrated, and ultimately validated with reference calibrated devices during blast operations. The sensing function principle is based on the push–pull principle of the mass–spring system of a total of three interferometers. A housing was designed and fabricated using 3D printing to allow the sensor to be operated in the field. Sensor calibration was carried out in an accredited laboratory. The measured sensitivity values were approximately 60 dB re rad/g for the vertical axis and 48–51 dB re rad/g for the horizontal axes in the frequency range of 1 to 50 Hz. The sensitivity values of the presented sensor are comparable to or surpass those of the Michelson-based sensors described in the state-of-the-art. The resulting amplitude–frequency calibration models of the sensor were assembled for all three orthogonal measurement axes so that the particle velocity can be measured. Finally, comparative measurement to reference seismic stations was carried out during a multi-hole bench blast at the Kotouc Stramberk quarry to validate the calibration models.

An Extremely Close Vibration Frequency Signal Recognition Using Deep Neural Networks

This study proposes the utilization of an optical fiber vibration sensor for detecting the superposition of extremely close frequencies in vibration signals. Integration of deep neural networks (DNN) proves to be meaningful and efficient, eliminating the need for signal analysis methods involving complex mathematical calculations and longer computation times. Simulation results of the proposed model demonstrate the remarkable capability to accurately distinguish frequencies below 1 Hz. This underscores the effectiveness of the proposed image-based vibration signal recognition system embedded in DNN as a streamlined yet highly accurate method for vibration signal detection, applicable across various vibration sensors. Both simulation and experimental evaluations substantiate the practical applicability of this integrated approach, thereby enhancing electric motor vibration monitoring techniques.

Interferometric Distributed Fiber Optic Vibration Sensor with Branching Sensing Optical Path Based on Time Delay Estimation for Disturbance Localization

Interferometric Distributed Fiber Optic Vibration Sensor with Branching Sensing Optical Path Based on Time Delay Estimation for Disturbance Localization

Precise disturbance localization of long distance fiber interferometer vibration senor based on an improved time–frequency variation feature extraction scheme

Locating intrusions with high accuracy is crucial for prompting long distance distributed optical fiber vibration sensing systems to practical applications in engineering filed. To achieve the high measurement accuracy and real-time performance simultaneously, in this paper, an intensity-modulated ultra-long distance distributed optical fiber vibration sensing system using an asymmetric dual Mach-Zehnder interferometer is experimentally established. More importantly, a positioning approach based on an ameliorated time–frequency feature extraction scheme is proposed with both theoretically analysis and experimental demonstration. In particular, an endpoint detection algorithm based on differential operation is firstly utilized to rapidly and accurately locate the endpoints of the received vibration signals. Thus the large-band width signals can be successfully acquired by setting an approximate window. Then, the ameliorated time–frequency feature extraction scheme based on a maximal overlap discrete wavelet packet transform is applied to eliminate the asymmetry of the large-band width signals, as it could lead to an erroneous positioning result when directly using a cross-correlation time delay estimation algorithm. Finally, the vibration positions along the sensing fiber link of the established sensing system can be successfully demodulated with the help of the extracted time–frequency features. To validate the effectiveness of the proposed scheme, vibration positioning tests were conducted in a real perimeter security scenario. And the results show that a mean positioning error of 11.12 m and a mean processing time of 0.276 s have been realized in a sensing length of 101 km. Thus, it is believed that through continuous technological advancements and refine algorithm optimization, the long distance distributed optical fiber vibration sensor founded on the proposed positioning strategy is poised to play an important role in the practical engineering applications.

Optical Fiber Vibration Sensor With Wide Detection Range Based on STDS Structure Designed by Mach–Zehnder Interferometer

Optical Fiber Vibration Sensor With Wide Detection Range Based on STDS Structure Designed by Mach–Zehnder Interferometer

Super-long-range distributed vibration sensor based on the polarimetric forward-transmission of light.

Undersea earthquake-triggered giant tsunamis pose significant threats to coastal areas, spanning thousands of kilometers and affecting populations, ecosystems, and infrastructure. To mitigate their impact, monitoring seismic activity in underwater environments is crucial. In this study, we propose a new, to the best of our knowledge, approach for monitoring vibrations in submarine optical cables. By detecting vibration-induced polarization rotation, our dual-wavelength fiber-optic sensing system enables precise measurement of acoustic/vibration amplitude, frequency, and position. As a proof of concept, a double-ended forward-transmission distributed fiber-optic vibration sensor was demonstrated with a single vibration source with a sensitivity of 3.4 mrad/µε at 100 Hz (20 m fiber on PZT), limit of detection of 1.7 pε/Hz1/2 at 100 Hz, sensing range of 121.5 km without an optical amplifier, spatial resolution of 5 m, and position error as small as 34 m. The vibration frequency range tested is from 0.01 to 100 Hz. The sensing system has several advantages, including elegant setup, noise mitigation, and super-long sensing distance.

Application of fiber Bragg grating sensing technology and physical model in bridge detection

In order to understand the application of fiber Bragg grating sensing technology and physical models in bridge detection, the author proposes an application research based on fiber Bragg grating sensing technology and physical models in bridge detection. The author first introduced the principle of fiber optic sensors, then analyzed the technology of demodulating fiber optic gratings, and discussed the application of fiber optic sensing technology in bridge detection, effectively improving the monitoring effect and safety performance of bridges. Secondly, in response to the problem that electrical sensors are difficult to meet the long-term monitoring requirements of bridge structures, it is proposed to use fiber optic grating vibration sensors to monitor the vibration status of bridges, and the feasibility of the scheme is demonstrated through theoretical and experimental results. FBG sensor parameters: Select a cylindrical mass block with a diameter of 3 mm and a height of 4 mm, weighing 0.6 g, a fiber length of 65 mm, and a pre stretching amount of 1.3 mm. Fiber Bragg grating sensors not only meet the requirements of frequency measurement range and temperature adaptation range, but also have advantages such as resistance to electromagnetic interference, simple appearance structure, convenient deployment, and good long-term stability. They have good engineering application prospects.

Long-range distributed vibration sensing using phase-sensitive forward optical transmission.

Long-range vibration sensing is an important tool for real-time structural health monitoring. A new, to the best of our knowledge, design of a distributed fiber-optic vibration sensor is introduced and experimentally demonstrated in this study. The proposed system utilizes the transmission of light in the forward direction for sensing, and a self-interference method for laser source simplification. To extract vibration information from phase modulation of light, two Mach-Zehnder interferometers (MZIs) are employed with a 3 × 3 coupler-based differential cross multiplication algorithm for phase calculation. A folded double-ended detection configuration allows the time-of-flight difference via cross correlation (CC) to provide vibration positioning. Experimental results demonstrate a sensing range of up to ∼80 km without optical amplification, accompanied by a position accuracy of 336 m.

Pattern Recognition of Distributed Optical Fiber Vibration Sensors Based on Resnet 152

Pattern Recognition of Distributed Optical Fiber Vibration Sensors Based on Resnet 152

Multi-longitudinal mode laser beat-frequency optical fiber vibration sensing system based on an FM radio module.

A multi-longitudinal mode (MLM) laser beat-frequency optical fiber vibration sensor using a frequency modulation (FM) radio integrated circuit module as the FM demodulation scheme is presented and demonstrated. To the best of our knowledge, this is the first case where a fiber-optic sensing system is combined with an FM radio module, and dynamic sensing is well achieved. As the carrier of the vibration source, the beat-frequency signal (BFS) generated by the MLM laser is transmitted to the FM radio module for FM and demodulation. The experimental results show that the system can successfully detect the vibration signal in the frequency range of 20Hz to 18kHz and accurately demodulate the waveform and amplitude of the vibration signal source. The minimum shape variable detected by the system is 20.67nm, based on the performance of the commercial FM radio module itself, which can effectively solve the problem of detecting tiny vibration. The idea of the optical fiber vibration sensing system is extremely innovative, with high sensitivity, high signal-to-noise ratio (SNR), good stability, and strong resistance to electromagnetic interference.

Temperature-Insensitive, Wide-Range Optical Fiber Vibration Sensor Based on Dispersion-Compensated Fiber

Vibration detection plays a vital role in the safety monitoring of engineering areas such as structural deformation of large buildings and railway tracks, and oil and gas spills. Herein, a temperature-insensitive optical fiber vibration sensor based on Mach-Zehnder interference is proposed and validated, which is achieved by utilizing a dispersion-compensated fiber (DCF). Specifically, single-mode fiber (SMF) is fused to both ends of a DCF to form an optical fiber vibration sensor, which is SMF-DCF-SMF (SDS) sensor. Under this sensing structure, this sensor’s vibration sensing characteristics, amplitude-frequency response, stability, repeatability and temperature-insensitive characteristics are investigated. The sensor can measure vibration frequency signals in the large frequency range of 0.1 Hz to 47 kHz by intensity demodulation. When the vibration frequency is 600 Hz, the maximum signal-to-noise ratio (SNR) of the sensor reaches 69 dB. In addition to that, the sensor can capture low amplitude vibration frequency signals down to 0.01 V. The proposed sensor has a wide measurement frequency range that effectively reduces temperature cross-sensitivity, and it has the advantage of being compact, low cost and easy to manufacture, with potential applications in health inspections, machinery and building saturation.

Optical fiber vibration sensor for bearing fault detection based on Sagnac interferometer

Bearings are crucial components in mechanical equipment, and bearing failure is one of the reasons for mechanical equipment safety accidents. In this work, an optical fiber vibration sensor based on Sagnac interferometer (SI) is proposed and applied to bearing fault detection. The polarization-maintaining fiber (PMF) is spliced between two single-mode fibers (SMFs) to form a SMF-PMF-SMF (SPS) fiber structure, which is connected with a 3 dB coupler to form a SI based on SPS fiber structure. The mass block is fixed in the middle of the PMF. When the monitored surface or structure vibrates, the stress of PMF will change and the Sagnac interference spectrum will be shifted, so that the vibration can be measured. The fabrication technology of sensor based on 3D printing is studied, and the structural parameters of the sensor are optimized through experiments and theoretical analysis. A vibration detection system and a rolling bearing vibration test platform based on SI and fiber ring laser are built. The experimental results show that the relative error between the experimental and theoretical results of healthy and faulty bearings is less than 1.60%, and the fault detection of bearings is realized. Temperature cross-sensitivity and stability of the sensing system are analyzed. The sensor has the advantages of simple structure, easy fabrication, anti-interference, etc, and has wide application prospects in engineering, machinery, security and other fields.

Design of Amplifier Circuit of Optical Fiber Sensor and Its Application in Cloud Computing of Mechanical Vibration Fault

Photoelectric detection technology has been widely used in industry, agriculture, medicine, and other fields. The signal collected by photoelectric signal detection equipment is weak and vulnerable to noise interference. Therefore, a preamplifier circuit with good performance is needed to amplify the original signal effectively. Firstly, considering that a single-mode fiber coupler is more sensitive to the length of the coupling region, a coupled optical fiber vibration sensor is designed. Secondly, the appropriate operational amplifier (Op-amp) is chosen based on the photodetector. By listing and selecting the OPA656 Op-amp produced by TI Company, the basic current and voltage conversion circuit of photoelectric detection equipment is analyzed. In addition, a basic trans-impedance circuit with a phase compensation function is proposed and the calculation method of optimal phase compensation capacitance is derived. Finally, in the process of monitoring the vibration data of equipment, cloud computing technology (fuzzy C-means clustering algorithm+MapReduce model) is used for distributed processing of mechanical vibration data. In the test, the coupled optical fiber vibration sensor designed with an amplifier circuit and moving coil vibration sensor are placed on the ship equipment at the same time, and the rubber hammer is employed to hit the surface of the ship machinery. The test results of the two sensors are the same, which proves that the optical fiber sensor designed in this study meets the requirements of vibration measurement.

Optical Fiber Vibration Signal Identification Method Based on Improved YOLOv4

In the traditional peripheral-security-early-warning system, the endpoint detection and pattern recognition of the signals generated by the distributed optical fiber vibration sensors is completed step-by-step and in an orderly manner. The method by which these two processes may be placed end-to-end in a network model and processed simultaneously to improve work efficiency has increasingly become the focus of research. In this paper, the target detection algorithm combines the endpoint-detection and pattern-recognition processes of the vibration signal, which can not only quickly locate the start and end vibration positions of the signal but also accurately identify a certain type of signal. You Only Look Once v4 (YOLOv4) is one of the most advanced target detection algorithms, achieving the optimal balance of speed and accuracy. To reduce the complexity of the YOLOv4 model and solve the dataset's unbalanced sample classification problem, we use a deep separable convolution (DSC) network and a focal loss function to improve the YOLOv4 model. In this paper, the five kinds of signals collected in real-time are visualized as two different datasets in oscillograph and time-frequency diagrams as detection objects. According to the experimental results, we obtained 98.50% and 93.48% mean Average Precision (mAP) and 84.8 and 69.9 frames per second (FPS), respectively, which are improved compared to YOLOv4. Comparing the improved algorithm with other optical fiber vibration signal recognition algorithms, the mAP and FPS values were improved, and the detection speed was about 20 times faster than that of other algorithms. The improved algorithm in this paper can quickly and accurately identify the vibration signal of external intrusion, reduce the false-alarm rate of the early-warning system, and improve the real-time detection rate of the system while ensuring high recognition accuracy.

Interferometer-Based Distributed Optical Fiber Sensors in Long-Distance Vibration Detection: A Review

In unmanned monitoring such as perimeter security, pipeline detection, railway security, and so on, it is still a challenging task to accurately locate the irregular vibration events. Compared with traditional vibration detection technologies, distributed optical fiber vibration sensors (DOFVSs) have superior advantages such as high spatial resolution, large monitoring range, good concealment, excellent flexibility, and simple sensing structure. The DOFVS can be mainly classified into two types, i.e., the interferometer-based DOFVS (IDOFVS) and the backscattering-based DOFVS (BDOFVS). In particular, IDOFVS has unique sensing advantages, such as high stability, simple structure, high sensitivity, and wide frequency response. In this article, the development of long-distance IDOFVS in recent years has been summarized. The sensing principle of IDOFVS has been theoretically explained. The specific classification of the IDOFVS and the corresponding sensing structures are described in detail. In addition, the long-distance distributed vibration sensing structure and processing algorithms, such as denoising and locating algorithms, are analyzed. Finally, the performance of recent long-distance IDOFVS has been compared and the development direction has been discussed.

A hybrid distributed optical fiber vibration and temperature sensor based on optical Rayleigh and Raman scattering

A hybrid distributed optical fiber vibration and temperature sensing system is proposed and experimentally demonstrated. By the system structure of optical time domain reflectometer (OTDR) and wavelength division method, the Rayleigh and Raman scattering light in multi-mode fiber (MMF) are extracted respectively for fiber vibration event detection and hot spot monitoring. The vibration event causes the polarization state and phase of the optical signal propagating in MMF to change, which makes the OTDR trace become smooth from the vibration position to the fiber end, so that it provides a reliable way to locate the vibration events. And then, a data processing method that averages the data within the vibration position and at least 50 continuous positions behind is proposed to improve the signal to noise ratio (SNR) of the vibration signal and finally by fast Fourier transform (FFT), the vibration spectrum is accurately obtained. In addition, the backscattered Raman Stokes and anti-Stokes signals are separated by the wavelength division multiplexer (WDM) and then they are converted into voltage signals. By conventional temperature demodulation algorithm, the temperature information along the MMF is obtained with measurement accuracy of about 1.5 °C. The experimental results show that the proposed hybrid distributed vibration and temperature sensing system possess good performance and as it is compatible with MMF that has been laid on the power cable, it is of great significance for engineering application.