Fabrication Of Microstructure Fiber Optic Sensor And Research On Multi-parameter Measurement

With the rapid development of optoelectronics and optical fiber communication industries,optical fiber sensing technology has attracted great attention.At the same time,a lot of novel optical fiber sensors continue to emerge and expand,which enriches the application of optical sensing,providing important research value for human exploration of special environments.Micro-structured fiber-optic sensor,a new type of sensor,usually has wide applications in the field of optical information.In this paper,the preparation and the sensing performance of micro-structure fiber-optic sensor,and the influence of various physical parameters are mainly studied and analyzed.Thus,three types of micro-structure fiber-optic sensors based on interference phenomena are designed.The specific research contents are as follows:(1)A new micro-structured fiber-optic sensor with high sensitivity for monitoring strain and small temperature range of Fabry-Perot cavity cascaded Bragg fiber grating is proposed.Firstly,four different microstructure Fabry-Perot cavities are compared and analysed.Secondly,a sensor is composed of four Fabry cavities with different lengths is selected,which sensitivity and linearity are 33.13167 nm/°C and 0.98935,respectively.Finally,the dual-parameter monitoring of temperature and strain can be realized by cascading FBG,which can better avoid the problem of cross-sensitivity.(2)In the experiment,the air bubble in micro-structure fiber was fabricated by a special discharge mode of the optical fiber fusion splicer,and then cascaded it with the Bragg fiber grating to form an intensity-modulated fiber-optic sensor.The liquid level,temperature,refractive index and curvature characteristics of the sensor are explored in detail.It is found that the refractive index and curvature parameters have no effect on the spectrum of the sensing structure,while the liquid-level and temperature parameters satisfy the linear relationship.The liquid-level sensitivity and linearity are-0.68987 d B/mm and0.9903,respectively.And the temperature sensitivity and linearity are-0.14872 d B/°C and0.99368,respectively.Finally,the liquid level and temperature were monitored respectively by demodulating the intensity of different characteristic peaks.(3)A enlarged-tapered micro-structured intensity-modulated fiber-optic sensor is proposed.The sensor composed of no-core fiber,seven-core and multi-mode fiber,which is constructed by programming the discharge intensity and advancing distance of the fusion splicer.Besides,the optimal length and the sensing characteristics of the optical fiber structure are explored.It is found that the curvature,strain and temperature have impacts on the sensor.Among them,the different effects of the different bending directions of the fiber structure on the spectrogram are used to realize the vector-type curvature monitoring.At the same time,the experiment further demodulates the influence of curvature,strain,and temperature parameters on the spectrum through a third-order matrix,avoiding the cross sensitivity and realizing independent monitoring.