Research On Sensing Characteristics Of Micro-Structure Optical Fiber Based On Surface Plasmon Resonance

Biological environment monitoring is currently a main concern in lots of countries around the world,and the improvement of monitoring means has also promoted the development of the sensor manufacturing industry.Among them,optical fiber sensors are favored by scientists due to their small size,lower loss,corrosion resistance,flexibility and anti-disturbance ability to electromagnetic interference.Surface Plasmon Resonance optical fiber sensors are widely used in biological molecular detection and environmental monitoring because of their high sensitivity to external environmental parameters.In this paper,SPR technology is combined with optical fibers and tilted fiber bragg gratings to make refractive index detection sensors,and the TFBG-SPR sensors are combined with chirp grating and Fabry-Perot interferometers to make a multi-parameter measurement probe.The main research contents of this paper are organized as follows:1.The attenuated total reflection and evanescent wave theories of beam propagation in different media are introduced,and the concept of surface plasmon waves of metal is discussed.The excitation principle and polarization characteristics of SPR sensors are provided,and the coupling structures and detection methods of different types of SPR sensors are respectively analyzed.2.Based on the SPR principle,a four-pole suspended core fiber refractive index detection sensor is designed,and three different polishing structures are established.The finite element technique is utilized to analyze the polarization characteristics and refractive index response of the sensor.Note that all three structures show high sensitivity.Finally,the effects of metal layer and fiber suspension pole thickness on the sensor are studied.With the increase of metal film thickness,the loss peak moves to the longwave direction,and the loss peak intensity decreases.In light of the increasing of suspension pole thickness,the loss peak steers to the shortwave direction,and the loss peak intensity decreases.3.The coupling principle of TFBG and the SPR sensing theory are elaborated,and a TFBG-SPR sensor is fabricated based on the SPR principle.The fabrication steps of the TFBGSPR sensor are illustrated,the polarization characteristics of the sensor are explored,and the refractive index response features of the sensor are further tested.The outcomes demonstrate that the sensitivity of the sensor reached 540.6 nm/RIU within the refractive index range of1.332-1.3787.4.A three-parameter measurement probe-type fiber optical sensor is devised by combining the TFBG-SPR sensor with a chirped fiber grating and two F-P interferometers.The sensing amplification principle of the optical vernier effect and the filtering principle of the chirped fiber grating are discussed.The fabrication steps of the two F-P interferometers are provided.The pressure,refractive index,and temperature responses of the sensor are experimentally tested and analyzed.The external packaging of the sensor is preliminarily designed,and the temperature cross-sensitivity characteristics of the sensor are analyzed.The experimental results verified that the constructed sensor has low crosstalk between the different detection parameters,a wide pressure detection range,and high sensitivity.