The basic principle and characteristics of optical fiber sensing

by:FOT     2020-07-07

basic principle and characteristics of sensing

fiber optic sensor technology research zui began in early 1977, the American institute of * has implemented by Charles. M。 Davis Foss (hosted by Dr. Optical fiber sensor system) Plan. Early fiber optic sensor for problems such as expensive, technical maturity, there is no widely used in engineering. The sensing technology has high sensitivity and accuracy, good resistance to electromagnetic interference ability, high dielectric strength and high temperature resistant, corrosion resistant, lightweight, flexible belt, etc. With the development of optical sensor technology and the improvement of technology, the application of sensor has been heavily promoted, many countries spare no effort to strengthen the research of fiber optic sensor. In recent years, sensor in mechanical, electronic instrumentation, aviation, petroleum, chemical, biological, medical, food and other industrial production process in the field of automatic control, on-line detection and fault diagnosis has been widely used.

in recent years, sensor was introduced into civil engineering because of its unique advantages, is widely used in building structure strain and bridge structure health monitoring, concrete mechanics performance test and inspection, etc. This paper introduces the basic principle of sensor and its application, the application of sensors in civil engineering is prospected.

1 basic principle of sensor

with the improvement of technological level, technology is relatively mature. The basic principle of sensor is the application of transmission combination of a sensing system of radio, film and television. The fiber optical sensing system usually consists of light source, , optical sensors, optical modulation components and signal processing parts [ 3] 。 Its working principle as shown in the figure below: light source the light through the into the light sensing element, the light sensor is affected by the ambient field and in the light of the change again into the light modulation, made out of its dispatch the parameters of the sensor to measure amplitude, phase, polarization, such as information, a process known as the photoelectric conversion process, zui after using microprocessor signal analysis.

as mentioned above can be seen that the sensing mechanism of fiber optic sensor and the sensing mechanism of electromagnetic sensor is similar, but the fiber optic sensor due to its measurement signal carrier is laser, its inside the fiber optic transmission, it is difficult to external electromagnetic field disturbance, therefore suitable for complex conditions of detection, and convenient and flexible operation, signal output automatically.

2 classification and characteristics of fiber optic sensor

2. The classification of fiber optic sensor 1

2. 1. 1 the classification of fiber optic sensor has different way of

according to the role of fiber in sensors can be divided into the sensor type and light transmission type two kinds.

sensor type sensor of transmission light effect not only, and photoelectric sensor. Because of the influence of the external environment on the itself, to measure physical quantities by , acting on the sensor of optical waveguide properties ( Light intensity, phase, polarization, wavelength, etc. ) By modulation. Sensor type sensor is divided into light stress system, phase modulation, vibration state modulation and wavelength modulation, etc.

2。 1. 2 preach type sensor

the measured object type sensor is to pass the modulation of light signal input of the , through light on output signal processing and measurement, this kind of sensor with additional sensor to measure physical quantities sensitive, as the only light components, must be attached to the modulation of light transmitted by fiber optic sensor to form a sensing element. Optical fiber sensor based on the measurement range can be divided into point fiber optic sensors, integral type sensor, three kinds of distributed sensors. Among them, the distributed sensor was used to detect the structure of the large strain distribution, can fast nondestructive measurement of the structure of the displacement, internal or surface stress and other important parameters. For the types of sensors in civil engineering at present basically has Math - Zender interferometric fiber optic sensor, Fabry - Pero cavity type sensor, Bragg grating sensor and so on.

2。 2 the characteristics of the fiber optic sensor

(1) high sensitivity, resistance to electromagnetic interference. Due to fiber optic sensor detection system is very difficult to interference by external field, and the optical signals in the transmission will not happen with the electromagnetic wave function, also is not affected by any electrical noise, because of the characteristics of sensor has been widely applied in the detection of the power system.

2 fiber has good flexibility and tenacity, so the sensor can make different shape according to the requirements of the site inspection.

(3) measurement of bandwidth, large dynamic range.

(4) portability is strong, can be made into different quantities of sensors, including acoustic field, magnetic field, pressure, temperature, acceleration and displacement, liquid level, flow, current, radiation and so on.

5] can be embedded in sex is strong, easy to connected to the computer and system, easy to implement the system of remote sensing and control.

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