Long-period fiber gratings inscribed in few-mode fibers for discriminative determination

Abstract

(dip 2). Due to the difference of the coupling mechanism involved in two dips, the shift of resonant wavelengths has different characteristics with the variation of the external environment parameter. The corresponding wavelength of dip 1 exhibits a red shift as the temperature increased. But for dip 2, the resonant wavelength has a blue shift. In addition, the two dips have different temperature and strain sensitivities. Therefore, discriminative determination of temperature and strain is realized by establishing the cross coefficient matrix, and the relative measurement error is less than 3%. What's more, we theoretically analyzed the reason why the two resonant wavelengths shift toward opposite direction with the increase of temperature and toward the same direction with the increase of strain.