Hongyan Wu

Position determination and monitoring of disturbance along distributed fiber optic sensors

Distributed Fiber Optic Sensor for Position Determination is a novel position sensor and can be used as a monitoring system in communication main of long distances. Single fiber is employed as the sensor in the system to pick up the disturbances in the environment. The principle of the system is that for a disturbance signal applied at a particular position along the fiber, the response, in the frequency domain, presents a series of periodic maxima and minima (or nulls). These minima depend on the position of the disturbance along a fiber. An intelligent, reliable and real-time signal processing method is needed in such a system to determine the position of disturbance. It is not enough to process the signal of the system just using FFT (fast Fourier transform) algorithm. By using power spectral estimation and wavelet transforming as the method of signal processing, the position of a random disturbance is successfully determined.

A research on polarization effects in a distributed optical fiber sensor disturbance location system

An analysis based on the Jones matrix theoretical analysis is presented to study the polarization effect of the distributed optical fiber sensor which was based on interferometer for disturbance location. A new improved distributed optical fiber location system is designed by using a Faraday rotation mirror ,the system is insensitive to the change of the polarization in the sensing part of the optic fiber, remove the linear birefringence and the orientation birefringence, the practicability of the system is increased.

A novel frequency-domain location method based on phase generated carrier

A novel distributed fiber-optic sensor system based on phase generated carrier (PGC) for determining the position of disturbance is presented. The configuration and the operating principle of the system are illustrated, and the location mechanism is analyzed. The location of certain disturbance is obtained by means of the PGC demodulation technology with a new frequency domain location algorithm.Theory analysis and experiment results show that the proposed technology can realize the detection and location of the disturbing signals rapidly and effectively. This method is simply and can be obtained easily, it can eliminate the differences induced by the instability of detection signal, and can greatly improve the position accuracy.

Multiple disturbance location in distributed fiber-optic sensor based on phase generated carrier

A novel distributed fiber-optic sensor based on Phase Generated Carrier (PGC) for determining the position of multiple disturbances is presented. The configuration and operating principle of the system is illustrated, the location principle and method for the detection system are analyzed. The system realizes the location of the multiple disturbances using the PGC demodulation technology. Theory analysis and experiment result show that the proposed technology can realize the detection and location of the multipoint disturb signals rapidly and effectively, this method is simply and can be obtained easily, it could increase the length of fiber-optic sensors which has high measurement sensitivity and location precision.

Parametric modeling in distributed optical fiber vibration sensing system for position determination

Abstract. Distributed optical fiber vibration sensing system is widely used as a monitoring system in communication cable and pipeline of long distances. When a vibration signal occurs at a particular position along the fiber, the response of the system, in the frequency domain, presents a series of periodic maxima and minima (or null frequencies). These minima depend on the position of the vibration signal along the fiber. Power spectral estimation methods are considered to denoise the power spectrum of the system and determine these minima precisely. The experimental results show higher accuracy of the position using a parametric model with appropriate selection of order p and q than just using fast Fourier transform algorithm.

Research on optical fiber microphone array based on Sagnac interferometer

Extensive attention has been paid to optical fiber microphone because of its especial merits, such as anti-electromagnetic interference, corrosion resistance, high sensitivity, safety and reliability. In the present study, a kind of optical fiber microphone array based on Sagnac interferometer using a broadband source is proposed. On the basis of the high sound quality and wide bandwidth of optical fiber microphones, the acoustic source localization theory is tested and verified in practice. The results prove the possibility of determine the location of acoustic source in a wide range of frequencies accurately. Besides its feasibility, the scientific value and application prospect, such as in battlefield and ultrasonic detection field, are great.

Research on the feature extraction and pattern recognition of the distributed optical fiber sensing signal

In this paper, feature extraction and pattern recognition of the distributed optical fiber sensing signal have been studied. We adopt Mel-Frequency Cepstral Coefficient (MFCC) feature extraction, wavelet packet energy feature extraction and wavelet packet Shannon entropy feature extraction methods to obtain sensing signals (such as speak, wind, thunder and rain signals, etc.) characteristic vectors respectively, and then perform pattern recognition via RBF neural network. Performances of these three feature extraction methods are compared according to the results. We choose MFCC characteristic vector to be 12-dimensional. For wavelet packet feature extraction, signals are decomposed into six layers by Daubechies wavelet packet transform, in which 64 frequency constituents as characteristic vector are respectively extracted. In the process of pattern recognition, the value of diffusion coefficient is introduced to increase the recognition accuracy, while keeping the samples for testing algorithm the same. Recognition results show that wavelet packet Shannon entropy feature extraction method yields the best recognition accuracy which is up to 97%; the performance of 12-dimensional MFCC feature extraction method is less satisfactory; the performance of wavelet packet energy feature extraction method is the worst.

The research on pattern recognition in distributed fiber vibrant sensor system

Distributed Fiber Vibrant Sensor System is a new type of system, which could be used in long-distance, strong-EMI condition for monitoring vibration and sound signals. Position determination analysis toward this system is popular in previous papers, but pattern recognition of the output signals of the sensor has been missed for a long time. This function turns to critical especially when it is used for real security project in which quick response to intrusion is a must. After pre-processing the output signal of the system, a MFCC-based approach is provided in this paper to extract features of the sensing signals, which could be used for pattern recognition in real project, and the approach is proved by large practical experiments and projects.

Application of Fiber-optic interferometer system in flyer plates velocity measuring

Based on the theory of Michelson optical fiber interferometer and Doppler frequency shift equations, author proposed a new optical fiber non-contact velocity measurement technique. And the new method was successfully used in flyer velocity measuring test. In the test, the optic fiber interferometer system not only measured the velocity which was around 3km/s but also acquired the full explosion progress of flyer plates. System adopts large pupil optical transceiver devices to improve the anti-deflection capability compared with the traditional self-focusing lens. Optical fiber noncontact velocity measurement equipment which was simple structure, high sensitivity and adaptability could be widely used velocity parameter measurement.

Research on distributed fiber-optic sensor based motor fault monitoring system

A new running condition monitoring method of motors such as generator sets, and aircraft engines, using distributed fiber-optic sensor was introduced in this paper. A Michelson Interferometer based fiber-optic sensor was constructed, which offered a high sensitivity of disturbance detection. Because the sensing arm of the sensor was composed of optical fiber, the distributed fiber-optic interferometric sensor provided a high capacity of anti-electromagnetic interference. The monitoring system had a simple structure, and the sensor could be fixed on the motor easily to monitor its running condition.