Research On Manufacturing Technology And Sensing Application Of Long-period Fiber Grating Based On Arc Discharge

Long-period fiber gratings play an important role in fiber communication,optical signal processing and fiber sensing systems.With the rapid development of all-optical communication network and super-sensing complex sensor network,long-period fiber gratings have become the most promising core optical device due to their advantages of small device size and high sensitivity.Traditional fabrication techniques of long-period fiber gratings mainly include mask writing using optical fiber photosensitivity,laser point by point writing using residual stress release and material densification and physical deformation using photoelastic effect.However,these technologies are gradually unable to suit the needs of optical fiber communication and sensing field,and a more efficient,lower cost and better performance long-period fiber gratings fabrication technology is urgently needed.In order to solve the above problems,a novel optical fiber device based on arc discharge effect is proposed in this paper.This device mainly includes the needle electrode tunable platform,optical fiber fixture and electric displacement platform.Its main characteristics are the adjustable distance between the electrode needles within the range of 0 mm?15 mm,the automatic opening and closing of the optical fiber fixture and the programmable distance and speed movement of the electric displacement platform.The minimum moving distance of the optical fiber is 20?m,which has the advantages of high flexibility and good stability.At the same time,a relatively perfect hardware and software supporting system is built.Based on the ARM Cortex-M3 architecture STM32F103RCT6microcontroller as the core,the hardware circuit including motion control system,arc discharge system and human-machine interaction system is designed.The core technology of 3000V controllable direct current high-voltage arc discharge is realized,and the effect of arc discharge is optimized.The operating process code of the microcontroller system is designed in Keil u Vision5integrated development environment.Based on the USART HMI software,developed a human-machine interaction interface and trigger events.The micro-cone long-period fiber grating was fabricated on a standard single-mode fiber by means of a fabrication device and the transmission spectrum of long-period fiber grating with smooth curve was obtained.In the transmission spectrum,the trough of the curvature at 1545.2 nm has the largest decreasing loss of-35.2 d B,and the bandwidth is 10.4 nm.The experiment results show that the diameter of the micro-cone decreases with the increase of arc discharge intensity and discharge time,while the width of the micro-cone increases with the increase of the distance between the two electrodes.On the other hand,a long period fiber grating cascaded peanut microstructure curvature sensor is proposed in this paper,which realizes the simultaneous response of the resonant wavelength and the resonant peak in the transmission spectrum to the change of curvature.The influence of peanut microstructures with different core diameters on the basic mode optical power was simulated and analyzed by optical simulation software RSoft.The results show that the loss rate of the basic mode optical power is faster when the core diameters of peanut microstructures are between 10?m and 25?m,and the loss rate of the basic mode optical power tends to be flat when the diameter is over 25?m.Curvature sensors with spherical microstructure,peanut microstructure and composite structure were fabricated on standard single-mode fiber by means of a fabrication device.The experiment results show that when the arc discharge intensity and discharge time are sufficient,the diameter of the peanut microstructure coating increases with the increase of the length of the end surface of the fiber beyond the central axis of the electrode needle.The experiment data of curvature measurement show that the sensitivity of resonant wavelength and resonant peak to curvature change is 9.622nm/m^-1 and 6.396 d B/m^-1,respectively,in the low curvature range of 0 m^-1?0.53 m^-1.In the high curvature range of 0.53 m^-1?0.91 m^-1,the response sensitivity of resonant wavelength and resonance peak to curvature change is 68.421 nm/m^-1 and 17.579 d B/m^-1,respectively.