基于特种光纤的迈克尔逊干涉结构的折射率传感器

AbstractDue to the advantages of anti-electromagnetic interference,simple structure,corrosion resistance and high sensitivity,optical fiber sensor has a position that cannotbe replaced by other sensors.Therefore,various fields for the application of opticalfiber sensor needs countless,optical fiber sensing technology research is in full swing,development is very fast.In this paper,a refractive index sensor based on theMichelson interference structure of SMF-TCF-FCF is proposed.TCF is a coupler inthe sensor structure,which excitations light into the cladding of FCF and excitationshigher-order modes at FCF to generate optical path difference.The end face of theFCF is coated with a silver film to enhance the reflectivity of the light.The opticalfield distribution was observed by Rsoft software,and the TCF length and FCF lengthwere respectively explored.The results show that when TCF is 0.5cm and FCF is2.5cm,the interference effect is the best.At the same time,the influence of differentrefractive index on the optical fiber sensor is explored by simulation.In practicalexperiments,the effects of TCF length and FCF length on the interference effect arealso studied,and the results are consistent with the simulation.NaCl solutions withdifferent refractive index ranges of 1.335-1.376 showed a good linear relationshipbetween refractive index and light intensity,with the linearity of 0.9856 andsensitivity of 225.9732dB/RIU.The sensor has different responses in differentsolutions with the same refractive index,and shows good stability in time andtemperature.Due to its low cost,easy operation,repeatability and high sensitivity,thesensor can be used for refractive index measurement in different environments.Key words:Michelson interferometer;Thin-core fiber;Four-core fibe;Refractiveindex sensor