| The all-fiber interferometric sensor has become a research hotspot because of its high sensitivity,simple manufacture,low cost and small size.This type of sensor is generally based on the mismatched structure of all-optical fiber core.By taking advantage of the mismatched coupling between the mode fields,it carries the external sensing information through the cladding mode,and then coupling back to the optical fiber core and interfering with the core mode,so as to realize the sensing purpose.However,the effective refractive index range of the cladding mode involved in sensing is limited by the sensor structure and the inherent material parameters of the optical fiber,thus limiting the application range of this type of refractive index sensor.In recent years,on the basis of existing sensing structures,exploring new sensing structures and using them to improve sensor performance has become one of the research directions of such sensors.Based on the structure of the all-fiber interferometric sensor,this paper proposes an embedded microcavity fiber-optic sensor structure.Through the combination of theoretical analysis and experimental research,a more in-depth theoretical and experimental research has been carried out on this type of sensor.The main work of this paper is as follows:1?The development status of interferometric optical fiber sensors in the fields of temperature,gas pressure and liquid refractive index at home and abroad is reviewed,and three types of hydrofluoric acid etching,femtosecond laser micromachining and focused ion beam etching Manufacturing method of optical fiber microcavity structure.2?Study on temperature sensing characteristics of embedded microcavity optical fiber sensor.The temperature sensing theory of embedded microcavity fiber sensor is analyzed,the theoretical model of single cavity and double cavity sensing is constructed,the optical field and energy distribution of the sensing structure are simulated,and the temperature experiment of embedded microcavity fiber sensor is studied.The experimental results show that the temperature sensitivity based on single cavity structure is 0.061nm/?,the temperature sensitivity of the double-cavity structure is 0.072nm/?,and the temperature sensitivity of the double-cavity structure is 0.011nm/? higher than that of the single-cavity structure.The single-cavity structure was encapsulated and sensitized to make a sensitized structure.The experimental results show that the temperature sensitivity after sensitization is 0.275nm/?,which is 4.5 times higher than that without sensitization.3?Study on gas pressure sensing characteristics of embedded microcavity optical fiber sensor.Based on the theoretical analysis of the air pressure of the embedded microcavity optical fiber sensor,the theoretical model of the single-cavity sensor is constructed,and the single-cavity sensor structure is simulated.Finally,the air pressure characteristics of the single-cavity sensor structure are studied through experiments.The experimental results show that the maximum pressure sensitivity can reach 0.175nm/kPa.4?Study on the composite sensing characteristics of the embedded microcavity fiber sensor.The principle of liquid refractive index sensing characteristics of the composite structure of the embedded microcavity optical fiber sensor was analyzed,and the model of the composite sensing structure was constructed,and the liquid refractive index characteristics of the composite sensing structure were studied in combination with the experiment.The experimental results show that when the center wavelength is 1540.0nm,the sensitivity in the refractive index range of 1.3351?1.3443 is 23.15nm/RIU,and the interference wavelength drifts to the long wave;the sensitivity in the refractive index range of 1.3443?1.3512 is-40.227nm/RIU,interference wavelength drifts to short wave.When the center wavelength is 1584.0nm,the sensitivities in the refractive index range from 1.3368?1.3512 are:35.42nm/RIU,-33.171nm/RIU and 60.64nm/RIU. |
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