Sensitivity Enhancement of Excessively Tilted Fiber Grating by Inner Cladding Perturbation

In this paper, we present theoretically a general method to enhance the sensing performance of the excessively tilted fiber grating (Ex-TFG) by inner cladding perturbation (ICP). The Ex-TFG is tuned to operate at the dispersion tuning point of the s-polarized TE
_0,m
and HE
_2,m
cladding modes. It is found that the sensitivity is resonance strength dependent when the sensing performance is evaluated by power measurement. The results show that the resonance strength and hence the sensitivity can be greatly improved by ICP together with tailoring the grating length. By this approach, we demonstrate, to the best of our knowledge, the highest sensitivity (18 742.3 dB/RIU) in the low refractive index region for the fiber grating-based sensors. In addition to this, the full-width at half-maximum and figure of merit show advantages over their counterparts of standard Ex-TFG. It is believed that this approach can be used to optimize the sensitivity when the Ex-TFG operates at other surrounding refractive index that is even than the cladding refractive index. This makes the Ex-TFG a very attractive platform for a wide range of sensing applications.