Yan Z, Sun Q, Wang C, Sun Z, Mou C, Zhou K, Liu D, Zhang L
Opt Express. 2017 Feb 20;25(4):3336-3346. doi: 10.1364/OE.25.003336.
We have investigated experimentally and numerically the temperature and refractive index (RI) sensitivity characteristics of excessively tilted fiber gratings (Ex-TFGs) in detail. Both results have shown that the temperature and RI sensitivities of Ex-TFGs are mode order dependent. For temperature sensitivity, the higher order cladding mode of Ex-TFG exhibited lower temperature sensitivity, quantitatively, the temperature sensitivities of TM cladding modes at the resonance wavelength around 1550nm are 9pm/°C, 6.8pm/°C, 5.6pm/°C and, 4pm/°C for cladding mode 28th, 31st, 35th, 40th, respectively, indicating the overall temperature sensitivity of Ex-TFGs were lower than that of normal FBGs. The SRI sensing results have shown that the RI sensitivity of Ex-TFG at the special index value could be improved by choosing the cladding mode with effective index close to the refractive index of the detecting medium. The SRI sensitivities at the effective mode index were 2250nm/RIU at 1.408, 864nm/RIU at 1.395, 1536nm/RIU at 1.380 and 1360nm/RIU at 1.355, for the cladding mode of 28th, 31st, 35th, 43rd, respectively. The experimental results have also shown the SRI sensitivity of Ex-TFG was increasing with increasing of the resonance wavelength.
我们已经通过实验和数值模拟详细研究了过度倾斜光纤光栅（Ex-TFGs）的温度和折射率（RI）灵敏度特性。两种结果均表明，Ex-TFGs的温度和RI灵敏度与模式阶次有关。对于温度灵敏度，Ex-TFG的高阶包层模式表现出较低的温度灵敏度，定量地说，在1550nm左右的共振波长处，TM包层模式的温度灵敏度对于第28、31、35、40阶包层模式分别为9pm/°C、6.8pm/°C、5.6pm/°C和4pm/°C，这表明Ex-TFGs的整体温度灵敏度低于普通光纤布拉格光栅（FBGs）。RI传感结果表明，通过选择有效折射率接近检测介质折射率的包层模式，可以提高Ex-TFG在特定折射率值下的RI灵敏度。对于第28、31、35、43阶包层模式，在有效模式折射率下的RI灵敏度分别为1.408时2250nm/RIU、1.395时864nm/RIU、1.380时1536nm/RIU和1.355时1360nm/RIU。实验结果还表明，Ex-TFG的RI灵敏度随共振波长的增加而增加。
