Research On SPR-MMI Combined Optical Fiber Sensor And Its Characteristics

Refractive index,as a physical quantity closely related to the composition of liquid concentration and optical properties,its accurate measurement has important significance in many fields.However,the refractive index of a liquid is not a fixed constant,and it is simultaneously affected by various parameters such as temperature.In the actual refractive index measurement process,temperature has also become one of the main sources of experimental errors,and the dual parameter sensor is one of the best ways to solve this problem.In recent years,many kinds of dual-parameter sensors have been proposed.Among them,the interference principle based on the existence of the mainstream is mainly due to the multimode interference(MMI)sensor has many sensitive parameters and is easy to make.However,due to the limitation of interference itself,it has the disadvantages of small measurement range and low sensitivity in refractive index measurement.In this regard,the surface plasmon resonance(SPR)fiber optic sensor has many advantages as a sensor with high refractive index sensitivity,and what we expect to see is to combine the advantages of MMI and SPR sensors to design a new type of sensor.This dissertation addresses the following issues:1.The SPR-MMI-based combined optical fiber sensor is designed and implemented.The optimal thickness of the gold film is 50 nm and the appropriate length of the sensing area is selected to be about 12 mm through simulation.2.The manufacturing method of single-mode-multimode-single-mode(SMS)optical fiber structure is given,and the process of gold-plating a certain thickness of optical fiber using ion sputtering and three-dimensional topography analyzer is introduced in detail,and successfully produced SPR-MMI combined fiber optic sensor.3.The sensing matrix of the SPR-MMI combined optical fiber sensor is derived,and the measurement methods and results of the four coefficients of the sensing matrix are given,including the measurement of the temperature and refractive index sensitivity of the SPR resonance peak,and interference to the SMS The peak temperature and refractive index sensitivity were measured,and the maximum refractive index sensitivity was-2061.6nm / RIU,and the temperature sensitivity was 37.9pm / ?.The accuracy of the sensing matrix was verified in heated ethanol,and the experiment was given.Comparison with theoretical results.