High-speed And Real-time Demodulation Of Broadband Spectral Interferometric Fiber Fabry-perot Sensor

Due to the advantages of small size,high sensitivity,and immunity from electromagnetic interference,optical fiber sensing technology is especially suitable for the structural health monitoring with harsh environmental characteristics such as high temperature,high pressure,and small space.The fiber Fabry-Perot sensor has more outstanding long-term stability and reliability because owing to its structural characteristics among varieties of optical fiber sensors.Additionally,the broadband spectral interferometric fiber Fabry-Perot sensor gradually become mainstream because of its high accuracy,large measurement range,and wide adaptation range.However,the sensor is not suitable for the high-speed and dynamic field.The reason is that the general demodulation system of broadband spectral interferometric fiber Fabry-Perot sensor must collect the complete interference spectrum through dense spectral sampling,and the amount of data is too large to slow down the speed of system.In order to solve this problem,it is a good method to change the collection way and the amount of collected data.The previous theoretical research shows that the maximum likelihood estimation algorithm of coarse spectral sampling can greatly reduce the amount of data in the spectrum,thereby improving the speed of demodulation while ensuring the accuracy of demodulation.As a result,this thesis focus on the needs of high-speed and high-precision demodulation based on the maximum likelihood estimation algorithm of coarse spectral sampling.And it researchs on high-speed and real-time demodulation system of broadband spectral interferometric fiber Fabry-Perot sensor from the hardware and software aspects,specifically completes the following work:(1)To meet the needs of high-speed and real-time demodulation system of broadband spectral interferometric fiber Fabry-Perot sensor,the parameters of the demodulation system are analyzed from the basic principle of the maximum likelihood estimation algorithm of coarse spectrum sampling.The key influencing factors such as demodulation speed,signal-to-noise ratio,measurement range,and accuracy are analyzed in deepth.As a consequence,the software and hardware parameter indexs of the demodulation system are obtained.(2)The key parameters such as gain and bandwidth of single-channel amplifier circuit,gain consistency and phase consistency of multi-channel amplifier circuit are analyzed in depth to meet the demand of coarse sampling of hardware circuits.And the gain bandwidth parameter model of the optical detection analog amplifier circuit is established.Then,the single-channel and multi-channel optical detection analog amplifier circuits are designed separately.The feasibility of the circuit is verified by electrical parameter testing on the basis of accomplishing circuit simulation analysis and actual board making.(3)The main factors affecting the speed of the software system are analyzed according to the software requirements of the maximum likelihood estimation algorithm of coarse spectral sampling.Afterwards,the software idea of fast calculation is proposed and the algorithm is optimized.The software's overall functional structure,workflow,and miscellaneous functional modules are designed based on the Lab VIEW platform.Furthermore,the feasibility of the software program is verified through the integration and debugging of the program.(4)In order to verify the performance of high-speed and real-time demodulation system of broadband spectral interferometric fiber Fabry-Perot,the overall verification experiment scheme of the demodulation system is proposed.Various experiments such as the system's signal-to-noise ratio,measurement range,static measurement accuracy,and dynamic demodulation speed have been completed successively to verify the indexes of the demodulation system and initially meet the expected design requirements.