Papers by Keyword: Fiber Optical Sensor

Abstract: Fiber Bragg Grating has advantages of high resistance to electromagnetic interference and high accuracy, which could obtain high-precision detection of the vibrations. A new type of accelerometer based on Fiber Bragg Grating (FBG) is proposed in this paper. The mechanical model of the accelerometer is designed as a single-degree-of-freedom system. The experiments show FBG accelerometer system has excellent stability and high durability. The acceleration sensitivity of the FBG accelerometer is 31.2pm/G.

Abstract: In our country, as the great threat caused by gas explosion or gas accident to the safety in coal mine production, the development of gas monitoring system is key to preventing accidents beforehand.. Putted into interferometer, the amplitude and the intensity of the incident ray carrying the information of gas concentration are divided many times by reflection and transmission, which results in many parallel beams in the form of the reflected light and the transmitted light. The concentration of the gas can be obtained by testing the light intensity signal . The experiment results show that an accurate measurement result which is capable for the gas concentration test in underground abominable conditions can be got by this mean. Particularly, based on multiplexing technique of optical fiber sensing, it is easy to build a sensor network. This method has an important significance and a good prospect of application and extension for gas monitoring and safety production in the coal mine.

Abstract: Polarization induced signal fading always has an influence up on the visibility of the interference stripe and the accuracy of system location in the distributed optical fiber oil &gas pipeline leak detection system. Base on distributed sensor system polarization characteristic, this paper analyses the visibility of the interference stripe with the changing of polarization. Designed a feedback control system based on double Mach-Zehnder is used to eliminate the input light polarization fading. This system can effectively suppress the polarization fading in fiber optical sensor, making interferometer fringe visibility tends to 1 and the equilibrium state of input light polarization always closes to the best input sate of interferometer.

Abstract: Surface quality of bearing ball is one of important factors to improve service performance. It is difficult to detect bearing ball surface defects with high precision and low cost by conventional methods. In this paper one new classification method based on optical fiber sensing technology was put forward from the longitudinal section angle. Inspection mechanism of Y-type and coaxial fiber sensor were analyzed, the mathematical models of the two fiber sensors were established and numerical simulations were realized by Matlab software. Influence of optical fiber parameters on light intensity modulation characteristic regulation was studied. Light intensity modulation characteristic experiments were done with specimens of different reflectivity and processing methods. The results show optical fiber sensing technique is an effective method to separate different surface of steel ball with extracting of two parameters displacement and surface reflectivity.

Abstract: Textile structures are extensively used in construction in forms of geotextiles. The retrofitting of existing masonry walls and soil structures is particularly important for earthquake protection of historic buildings and protection of earthworks against landslides. Unreinforced masonry structures are highly vulnerable because being originally designed mainly for gravity loads they often cannot withstand the dynamic horizontal loads in case of strong earthquakes. Soil structures, such as embankments, are subjected to landslides after heavy rainfalls or during earthquakes. Hence the necessity to develop efficient methods for the retrofitting of existing masonry buildings and earthworks and of related monitoring systems to possibly prevent the structural damage. To solve the above issues new multifunctional textile structures are being developed for application in construction for the retrofitting of masonry structures and earthworks, integrating a combination of different functions, including structural health monitoring.

Abstract: Adaptive fiber-optic interferometer which is based on multimode optical fiber as a sensor and diffusion holograms recorded in semiconductor photorefractive crystal CdTe:V without any electric field is developed. The interferometer sensitivity achieved is only 5.7 times less then highest sensitivity which is possible only in non-adaptive lossless classical interferometer. A practical detection limit is equal to Hz W nm 10 0 3 5 − × . , which allows to broadband detecting of an object’s displacement of order 0.2 nm or deformation of order 2 pε with using light sources having only 5 mW optical power.