Fiber grating is a section of optical fiber, and its refractive index changes periodically in its core. According to the mode coupling theory, when the central wavelength signal lB is reflected by the fiber grating (where lB is the central wavelength of the fiber grating, T is the grating period, and N is the effective refractive index of the fiber core), it is related to the grating period T, N is the effective refractive index of the fiber core, which will lead to the central change of the reflected wavelength when the temperature and stress of the fiber grating change due to external measurement. That is to say, the change of all central wavelengths reflected by fiber grating reflects the change of external detection signals. The wavelength of the sensor refers to the wavelength of the peak in the FBG reflection table. The peak wavelength varies with strain and temperature. When the temperature rises or in an emergency, the peak wavelength of FBG sensor becomes longer. If the sensor with the peak wavelength of 1535.050nm is heated from 25 degrees Celsius to 35 degrees Celsius, the peak wavelength of the sensor will rise to 1535. 150nm (change every degree Celsius 10pm). Most FBG's are systematically queried and operated within the window range of 50 nm, from 1520 nm to 1570 nm.
Application of Fiber Bragg Grating Sensor Fiber Bragg Grating is used in bridge, communication, construction, machinery, medical treatment, navigation, aerospace, mining and other fields. Can play an important role, so it has broad application prospects. So far, great achievements have been made in the theoretical research of fiber Bragg grating, but the research on its practicability needs to be further deepened. The measurement of the small deviation of Bragg wavelength of sensing grating is the key technology of fiber Bragg grating sensor for practical use. On this basis, several methods of wavelength demodulation of fiber Bragg grating are introduced in this paper. Among these methods, although the strain wave demodulation method is simple, it is difficult to further improve its sensing accuracy; The spectrum coding/proportional demodulation method can obtain higher resolution, but it requires the use of low-intensity light source, and at the same time, considering the attenuation of light energy, the application of various coping methods and technologies is limited; The unbalanced scanning Michael temperature interferometer demodulation method has the advantage of high precision. The wavelength information of the sensing grating can be decoded and detected urgently, and the sensing resolution can be greatly improved by demodulation with this method. Fiber Fabry-Perot A, which is very harmonious in measuring the reflected wavelength of fiber grating sensors, can directly convert wavelength signals into electrical signals, and has the advantages of small size, low price, high sensitivity, high utilization rate of light energy, simple operation and wavelength shift detection technology suitable for engineering use ... This method has great prospects in the field of fiber sensing. In the engineering health detection, the traditional monitoring method usually adopts the way of installing emergency slices on the basis of buildings, and the emergency slice technology is quite mature, but with the expansion of application scope, many shortcomings have also been exposed, such as: complicated connections, and the network of difficult groups is easily disturbed. Electromagnetically. In recent years, with the gradual maturity of optical fiber sensing technology, the advantages of fiber grating sensors are becoming more and more obvious. More and more engineering tests begin to use fiber grating sensors. The advantages are as follows: Compared with the traditional emergency film, the fiber grating sensor:
1. The fiber grating sensor adopts wavelength coding, which can contact multiple sensors on one optical fiber and facilitate networking.
2. Optical fiber connection is adopted between the fiber grating sensor and the analysis instrument, and the signal is not interfered by electromagnetic interference.
3. The main material of fiber grating sensor is Shi Ying, which is suitable for use in harsh environment with strong corrosiveness.
4. Long service life, up to 15 years or more.