Research On Sensing Characteristics Based On No Core/hollow Core Fiber Mode Interference

In recent years,special optical fibers play a great role in the field of optical fiber sensing due to their advantages such as low loss,low nonlinearity and high bandwidth.The no-core fiber only has a cladding structure with a uniform refractive index distribution.Compared with the ordinary optical fiber,the hollow-core fiber has a hollow air core structure.Both are more sensitive to the external environment,and they are more and more widely studied and applied in the field of sensing.In this paper,based on summarizing the research status of in different sensing fields of no-core fiber and hollow-core fiber at home and abroad.Three kinds of no-core/hollow-core fiber sensors are designed and implemented.The sensing characteristics of temperature,refractive index and curvature are analyzed in depth.The specific contents include:Firstly,the structural parameters of no-core fiber and hollow-core fiber are introduced.The transmission modes of no-core fiber and hollow-core fiber are analyzed and simulated.The sensing principles of temperature,refractive index and curvature of no-core fiber and hollow-core fiber sensor are analyzed.Secondly,a symmetric waist-enlarged no-core fiber sensor is designed and fabricated.The transmission spectra of no-core fiber sensors with the same waist-enlarged size and different lengths are studied and its transmission mode is analyzed.Temperature,refractive index and curvature sensing experiments are built.Sensing characteristics of the temperature,refractive index and curvature are analyzed.Thirdly,a symmetric waist-enlarged hollow-core fiber sensor is designed and fabricated.The transmission spectrum and mode changes of hollow-core fiber sensors with the same waist-enlarged size and different lengths are studied and analyzed.Its temperature,refractive index and curvature sensitivity are compared with those of symmetric waist-enlarged no-core fiber sensor.Finally,a cascaded core-offset splicing no-core-hollow-core-no-core fiber structure sensor is designed and fabricated.The transmission spectra of sensors with different core-offset are studied.The temperature,refractive index and curvature of the sensor are measured and linearity are analyzed.The response characteristics of three sensors to temperature,refractive index,and curvature are compared.