Study On Preparation And Sensing Characteristics Of Tilted Fiber Bragg Grating

Tilted fiber Bragg grating (TFBG) is a kind of novel optical fiber passive component whose grating patterns have a certain angle relative to the fiber axis perpendicular. TFBG has not only advantages of characters of ordinary Fiber Bragg grating (FBG), such as high sensitivity, small in size, anticorrosion, anti-electromagnetic interference, but also has advantages of characteristics of Long period grating (LPG), sensitive to surrounding refractive index (SRI). Therefore, TFBG have both the sensing advantages of FBG and LPG.The coupled-modes formulation of TFBG including coupling between the core-guided mode and the backward-propagating mode, coupling between fiber core-guided mode and fiber cladding mode, coupling between fiber core-guided mode and radiation mode were obtained according to the coupled mode theory. Then, sensing principles of temperature, tension and refractivity of TFBG were analyzed, respectively.TFBG samples with different angle were prepared by UV written and rotating phase mask method. The relationship between internal tilted angle and external tilted angle was studied. Moreover, their influences on grating characteristics were investigated, respectively. Temperature, tension and refractivity characteristics of TFBG including Bragg resonance, ghost mode resonance and high-order modes were experimented and researched, respectively. The experiment results showed that Bragg resonance and ghost mode resonance have consistent sensitivity of temperature and tension but not sensitive to SRI. The High-order modes of TFBG have sensitivity of SRI but not sensitive to temperature and tension. Therefore, we can simultaneously measure tension, temperature and SRI by Bragg resonance, ghost mode resonance and high-order modes. In this way, we can not only cut the cost of sensor preparation but also solve cross sensitivity problem effectively.