Two-channel Optical Fiber Surface Plasmon Resonance Refractive Index Sensing

Fiber optic sensing technology has been a hotspot issue in the information society,the resulting fiber Surface Plasmon Resonance(SPR)sensor widespread application in a lot of fields because of its characteristics of light weight,excellent resisting interfere capacity.inexpensive cost and high sensitivity.In this paper,two dual-channel optical fiber SPR refractive index sensor structures based on composite films were designed and can finally achieve dual-channel refractive index measurement.The main work of this paper is as follows:1.Based on the theory of optical fiber surface plasma resonance,two dual-channel optical fiber SPR sensor structures with side polished,cascaded multimode-single mode-multimode(MSM)structure were designed.Based on the theory of multilayer reflection,the characteristics of the composite film were studied and Combined with the theory of dual-channel optical fiber transmission,the theoretical transmission spectrum of the dual-channel optical fiber SPR sensor was analyzed.2.Based on the side effection structure,the dual-channel optical fiber SPR sensor using different composite films as the sensing channels(Ag-ITO composite film,Au-Ti O₂ composite film)was simulated and analyzed by the finite difference time domain method.The results show that selecting dual-channel sensing and appropriate Composite film can improve the sensor's resonance depth,sensitivity and other performance,the problem of resonance wavelength crosstalk can be effectively avoided.Based on the MSM structure,the sensing channels I and II use Ag film and Ag-ITO composite film dual-channel optical fiber SPR sensor for simulation analysis.The results show that the length of the sensing area in the actual production is more appropriate to choose 5-10 mm.From the simulation of the dual-channel fiber optic SPR sensor with the same refractive index,it is concluded that the sensitivity of sensor's channel I is about2466.1 nm/RIU,the sensitivity of sensor's channel II is about 2436.4 nm/RIU and other performance.The dual-channel sensor of this structure avoids the problem of resonance wavelength crosstalk under a large refractive index,and also helps to further develop the array-type multi-channel sensor structure.3.A dual-channel optical fiber SPR sensor based on MSM structure is fabricated,apackage the sensor and an experimental test system was set up.The results show that the sensitivity of channel I of the dual-channel sensor under the same refractive index is about 1186.51nm/RIU,and the sensitivity of channel II is about 1147.27nm/RIU and so on.The performance of the dual-channel sensor under different refractive indexes was tested,and the resonance wavelength crosstalk problem was analyzed and verified.Finally,the problem of inaccurate measurement caused by oxidation caused by the Ag film as the sensing channel is analyzed,and the sensor is protected against oxidation.