Tapered optical fiber is widely used in optical sensing,especially pressure sensors,which takes advantage of the power loss of the fiber after being bent by external force.The bending loss of the adiabatic linearly tapered optical fiber at various positions,especially in the transition region,were simulated using finite element method.The beam envelope method of the wave optics module of the simulation software was used to study the bending loss,which ensured the accuracy of the calculation and reduced the calculation amount greatly.The numerical simulation results show that the bending loss in the core mode cutoff region of the fiber is larger and the stress sensitivity is greater than those in other regions.This is because that there is mode evolution process in this region,which the critical angle takes the smallest value and the adiabatic condition is most easily broken.Therefore,the pressure sensor can select this specific region as the sensing location to achieve higher sensitivity.In addition,the diameter of the fiber in the core mode cutoff region is tens of microns,which can provide better mechanical structure strength compared with the waist region,so as to achieve higher mechanical stability.Moreover,the fiber with higher bending sensitivity can be found by changing the profile of the transition region of the tapered optical fiber,that is,the size of the local tapered angle,for the experimental fabrication of the sensor.These preliminary theoretical simulation results can provide a valuable reference for the design and application of tapered optical fiber sensors.
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