Research On Fiber-optic Intermode Interferometric Sensor Based On S-cone

Optical communication technology and sensing technologies are both changing dramatically,optical fiber sensing technology,as a new technology,has a very important impact in medicine,aerospace,engineering,Internet of things and other fields.After decades of research and development,optical fiber sensor technology is becoming more and more mature.As an important part of this technology,optical fiber sensor has attracted the attention of scholars from all walks of life.Because of its many good properties,such as compact structure,light weight,anti electromagnetic interference,remote transmission and low cost,ithas broad application prospects in various fields.In this paper,three kinds of inter mode interference optical fiber sensors with S-taper and spherical structure are fabricated by using thin core optical fiber,multi-mode optical fiber and single-mode optical fiber,respectively.The sensing performance of the sensing structures made of three different optical fibers is compared,and the sensing structures are analyzed in detail.The main part of this paper are written below:1.An inter mode interference sensor based on cascaded thin core S-taper and spherical structure is designed and fabricated.The S-taper is the mode excitation structure and the spherical structure is the mode coupling structure.Based on the theory of inter mode interference,the sensing experiment is carried out and the interference spectrum is analyzed.The experimental results show that the refractive index sensitivity is up to-70.392nm/RIU,and has a high linearity;The highest temperature sensitivity is 0.0802 nm/?.2.An optical fiber interferometric refractive index sensor is designed and fabricated based on the cascaded multimode S-taper and spherical structure.The S-taper excites cladding mode,and the spherical structure couples part of the cladding mode back to the core,which realizes mode interference.We analyze the interference spectrum and observe the drift of the interference trough to reflect the changes of the external environment The sensitivity matrix is constructed by using the different refractive index sensitivity and temperature sensitivity of different interference wave trough and wave crest,so as to solve the problem of temperature cross sensitivity.The experimental results show that the highest refractive index sensitivity of the sensor structure is-181.09nm/RIU;The highest temperature sensitivity is 0.0319 nm/?.3.An optical fiber interferometric refractive index sensor cascaded with a single-mode S-taper and a spherical structure is designed and fabricated.The spherical structure was produced by welding machine discharge,and then welded with single-mode S-taper.The sensor structure is simulated by Rsoft,and the optical path is simulated to observe the process of cladding mode from excitation to coupling and realize mode interference.The experimental results showthat when the refractive index range is 1.3316-1.3516,the refractive index sensitivity can reach-321.53nm/RIU;The maximum temperature sensitivity is 0.06821nm/? in the temperature range of 65?-95?.