Zhifan Yin

Fiber-Bragg-grating-based seismic geophone for oil/gas prospecting

A new type of fiber Bragg grating (FBG) sensor–based seismic geophone is presented. The major application of this FBG geophone is in the seismic reflection survey of oilfield exploration to detect the seismic waves from the Earth. The customized FBG geophone prototype that is demonstrated consists of two FBG sensor/demodulation grating pairs attached on a spring-mass mechanical system. The sensor performance is characterized in the laboratory in comparison with the conventional geophone. The FBG sensor is resistant to electromagnetic interference and has higher frequency response bandwidth and sensitivity than a conventional moving-coil electromagnetic geophone. The field tests results taken in the oil field show the sensor system frequency response bandwidth at 10 to 100 Hz in Shallow layer and 10 to 140 Hz in medium and deep layer separately.

Fiber Bragg grating sensors for seismic wave detection

The work presented in this paper demonstrates a sensing technology for unattended seismic sensors based on the optical fiber Bragg grating. This kind of sensor can perform accurate measurements of the seismic activity due to their high sensitivity to dynamic strains caused by small ground vibrations. One of the applications is its deployment in the battlefield remote monitoring system to track and geo-locate the presence of personnel, wheeled vehicles, and tracked vehicles. The experimental data of the field test are shown as well as the comparable result with commercial seismic sensors.

A novel fiber Bragg grating based seismic geophone for oil/gas prospecting

In this paper a new type of fiber Bragg grating (FBG) sensor based geophone is introduced. This FBG geophone is mainly used in the seismic reflection survey of oilfield exploration to detect the motion of the earth. The basic detection principle of the seismic survey and the fiber Bragg grating sensing technique is explained in brief. An eight channel FBG sensor based geophone system is developed and demonstrated in both laboratory tests and field tests. The experimental results show the sensor system frequency response bandwidth at 10-100Hz in shallow layer and 10-140Hz in medium and deep layer separately. A high dynamic range and good signal to noise ratio are also observed in the experiment.

Optical fiber gas sensor for remote detection of CH4 gas in underground mines

An optical-fiber-based gas sensor for CH4 gas real-time monitoring has been developed and tested. A long-distance silica fiber link with compact single-path or multi-path gas cells has been employed in conjunction with a wavelength-tunable. InGaAsP DFB laser diode at 1.64μm (at the R(6) absorption peak of methane) to achieve highly sensitive remote interrogation of CH4 with potential application in the mining complexes and residential areas. By wavelength modulation with the DFB laser diode, multi-path gas cell and a self-design processing circuit, sensitivities of less than 1% of lower explosive limit (LEL) had been achieved in the laboratory.

Detection of seismic signal using fiber Bragg grating sensors

An unattended seismic sensor based on optical fiber Bragg grating (FBG) sensing technology is presented in this paper. One of the applications is its deployment in the battlefield remote monitoring system to detect the presence of personnel, wheeled vehicles, and tracked vehicles. The customized FBG sensor prototype is demonstrated which consists of two FBG sensor/demodulation grating pair attached on a spring-mass mechanical system. The sensor performance is evaluated in laboratory and the field tests were carried out in the shooting range using the conventional military Rembass-IIS/A sensor (remotely monitored battlefield sensor system II seismic acoustic sensor) as the benchmark. Personnel and a series of vehicles were used as targets. The experimental data of the field test show that the FBG sensor averaged a 30.20 % greater detection range than the Rembass-IIS/A sensor. It is hoped that the FBG sensor system will be a promising tool for real time monitoring system in the battlefield applications.

Seismic wave detection system based on fiber optic sensor

In this paper we will demonstrate our fiber Bragg grating (FBG) accelerometer system in seismic wave detection applications. Optical fiber sensors using fiber Bragg grating have a number of advantages such as immune to electromagnetic interference, lightweight, and low power consumption. Most important, the FBG sensor has high sensitivity to dynamic strain signals and the strain sensitivity can approach sub micro-strain. The basic principle of the FBG seismic sensing system is that it transforms the acceleration of ground motion into the strain signal of the FBG sensor through mechanical design, and after the optical demodulation generates the analog voltage output proportional to the strain changes. The customized FBG seismic sensor prototype is described, which includes the electro-optical design, mechanical design and the hardware and software interface of the sensor system. The laboratory evaluation of the system is performed systematically on a commercial vibration stage. Studies of the sensor properties show that the sensor has a high sensitivity (2500 mV/g at 90 Hz) to the acceleration signal, a large dynamic range (80 dB), the good linearity and stability after device integration and packaging.

A civil structural monitoring system based on fiber grating sensors

Optical fiber sensors based on Fiber Bragg Grating (FBG) technology have found many applications in the area of civil structural monitoring systems, such as in bridge monitoring and maintenance. FBG sensors can measure the deformation, overload and cracks on bridge with a high sensitivity. In this paper we report on our recent work a structural monitoring system using FBG sensors. Basic theoretical background and design of the system is described here, including the light source, FBG sensors, demodulator sensors, signal detection and processing schemes. The system will be installed on a major arch bridge currently under construction in Shanghai, China for long-term in situ health monitoring. The system schematic arrangement on the bridge is introduced in brief. Simulation experiments in the laboratory were carried out to test the performance of FBG strain sensors. The sensor response shows excellent linearity against the strain imposed on it. Traffic and overload monitoring on bridge using FBG sensors is also discussed and planned for the near future.