Micro Fiber Sensing Research For Marine Environment Parameter Monitoring

The ocean is an important part of the earth system,and the parameters of the marine environment are related to many aspects such as underwater organisms,atmospheric environment,and underwater military equipment.With the advancement of the "14th FiveYear Plan" marine Internet of Things project,the research on underwater sensing equipment has become a hotspot in today's era.Traditional Marine environmental monitoring equipment is mainly electrical,with large volume,weak anti-electromagnetic interference ability and high cost.Although the existing optical sensor can make up for the above shortcomings,there are still some shortcomings such as weak compactness of the sensor system,weak impact resistance of the structure and low response sensitivity.In order to solve the above problems,starting from engineering application and aiming at the monitoring needs of Marine environmental parameters,this paper adopts mathematical modeling,simulation analysis and experimental verification methods based on the microfiber sensing structure to develop a new type of ocean parameter sensor to achieve all-round Marine monitoring.Firstly,this paper introduces the research progress of ocean sensor and optical fiber sensor technology in detail,and compares the advantages and disadvantages of scattering sensor,fiber grating sensor and interference sensor.An optical sensing structure based on microfiber-Michelson interferometer was proposed,and its optical transmission characteristics were analyzed.The influences of the waist diameter,waist length and the change rate of the cone on the structure characteristics of the microfiber were simulated and verified by experiments,and the structural parameters of the micro-nano fiber were optimized.Furthermore,encapsulation of microfiber structure is proposed to improve its environmental adaptability and pressure response sensitivity.In this paper,we compared the encapsulation on fixed and free state,the single side with all the surface stress,different thickness of the encapsulation and packaging in the shape of stress sensitization effect.The pressure(depth),temperature and salinity sensing responses of encapsulated microfiber sensing structure are simulated and analyzed.The simulation results show that the encapsulation can sensitize the pressure sensor,and the sensitivity of the sensing structure can be controlled according to different simulation methods to meet different measurement needs.Finally,we prepare micro-nano fibers with waist length,waist diameter and taper zone change rate of 8.5mm,6um and 0.3 respectively,and encapsulate them with PDMS.The transmission spectra of the sensor as a transmission sensor and a reflective sensor are tested,and the pressure and temperature are measured with a reflective OM-MI sensor structure.The experimental results show that the sensor can be used to measure the depth 1.48nm/MPa and temperature-3.28nm/? of ocean environment.The pressure sensitivity of all surfaces of the sensor can reach 2.63 nm/MPa when subjected to force.It has the advantages of simple structure,low loss,easy integration,easy expansion,high repeatability,good stability,and strong environmental adaptability.