Study On Temperature And Stress Sensing Characteristics Of Symmetrical Fused Tapered Fiber Grating

With the development of sensing technology,traditional sensors are limited in many applications,and fiber-optic grating sensors are widely used because of the advantages that many traditional sensors do not have.However,the stress and temperature cross-sensitive issues of ordinary fiber-optic grating sensors have always been one of the important factors affecting their measurement accuracy.Symmetrically fused tapered fiber grating can solve the problem well.In this paper,a fiber-optic grating with a symmetrical double conical structure is prepared by the fusion pull cone technology.First,the theoretical model of sensing characteristics is established by combining the transmission matrix method,and a detailed theoretical derivation of its sensing characteristics is given.Secondly,the factors affecting the radon coefficient are studied,and the spectral characteristics of the symmetrical melt-pull-cone fiber gratra are analyzed to discuss the causes of dense modulation at the short wavelength of the spectrum.Then the simulation studies the reflection spectrum effect of temperature and stress on the fiber optic grata of symmetrical melt pull-cone under different conditions.The results show that the ripple coefficient of the symmetrically fused tapered fiber grating is similar to the linear relationship between the amount of change in the length of the grating.Dense wavelength modulation occurs at short wavelengths of the grating reflect spectrum.The reflected wavelength and stress and temperature of the symmetrically fused tapered fiber grating are linearly proportional to the linear ratio,while the reflection spectral bandwidth is linear only to the stress.In view of the low stress sensitivity in simulation,this paper proposes a scheme to increase the fiber radius difference of the sensing cone area of the polymer coating cone and increase the sensitivity,and the simulation stress sensitivity reaches 0.31836nm/N.Finally,this paper makes a multi-symmetric fused tapered fiber grating by arc discharge method to study its stress and temperature sensing characteristics.The grating reflection spectrum indicates that due to the "thermal wipe" effect,part of the grating is erased,resulting in multiple transmission peaks in the reflection spectrum.The experimental results of multiple gratings show that the symmetrically fused tapered fiber grating has the characteristics of spectral bandwidth sensitivity to axial stress and temperature insensitivity.The grating package experiment proves that the grating package can protect the grating and improve the stress sensitivity,which is consistent with the theoretical analysis.