Research On The Sensing Characteristics Of Tilted Fiber Grating

TFBG sensing technology was developed,which had great research value and application prospect in many fields.Because of its small size,low loss and easy to form a new component with other devices,it has important value in various fields.In addition to their own many advantages,more and more people pay attention to.TFBG,as a shortperiod FBG with a structure different from the ordinary structure,is different from the ordinary structure because its grating is different from the ordinary type,which leads to the unique coupling mode in the transmission of light and thus has some advantages and sensing characteristics that the ordinary fiber grating does not have.The special optical properties of TFBG due to its special structure make it adapt to the environmental requirements under different conditions.In this paper,based on the coupled mode theory of TFBG,the transmission spectrum of TFBG is simulated,and the effects of structural parameters such as tilt Angle,grating length and period,and refractive index modulation depth on the transmitted light power,frequency band width,central wavelength and other factors of TFBG are obtained.It is calculated that(1)with the increase of inclination Angle,the resonant peak wavelength of the core mode and each cladding mode will shift due to this factor,and their transmission depth will gradually become smaller,that is to say,the transmission loss will be smaller.(2)The grating length increase has no effect on the position of each mode resonant peak in the transmission spectrum and does not lead to wavelength drift,but its transmission loss increases.(3)The grating period will affect the position of each resonant peak,and the transmission depth of the resonant peak of the core mode and the cladding mode will change slightly.(4)With the increase of modulation depth,the resonant peak transmission depth of core mode and cladding mode will increase to a certain extent,and the increase range of transmission power at the peak of core mode is greater than that at the peak of each cladding mode.But the spectral position is not affected by it.According to the simulation results and combined with the theory,we customized TFBG and designed experiments to carry out exploration,and respectively carried out research on temperature and strain sensing characteristics.It is found that(1)when the temperature changes,the resonant wavelength of the core is redshifted,and some cladding modes are also redshifted.The relative wavelength of the core mode and "ghost mode" has no obvious change,and the coupling strength of the mode does not change.At the same time,the shape and bandwidth of the transmission spectrum do not change due to the change of temperature.(2)When the strain changes,the resonant peak wavelengths of each mode have a red shift,showing a good linear relationship.The relative wavelengths of the two resonant peaks have no obvious change,and the shift changes are nearly the same.The shape and bandwidth of the transmission spectrum are almost unchanged,and the transmission depth is also basically unchanged.