为了检测柴油煤油混合油的折射率特性, 利用耦合模理论分析长周期光纤光栅折射率传感特性, 建立长周期光纤光栅中心波长、透射谱峰值损耗与混合油品中柴油含量的关系.结果表明: 在混合油中, 随着柴油含量的增加, 长周期光纤光栅波长发生蓝移, 当柴油含量达到使混合油折射率等于包层折射率时, 中心波长漂移最大, 柴油含量每改变1%, 中心波长平均漂移0.622 7 nm; 柴油含量继续增加, 混合油折射率大于包层折射率时, 光栅中心波长基本保持不变, 但是峰值损耗逐渐增大,带宽减小, 之后柴油含量每增加1%, 峰值损耗线性增加0.154 6 dB.该方法在检测混合燃料各组分含量具有潜在的应用前景.

In order to detect the characteristics of refractive index of the oil mixed kerosene and diesel, the sensitive features of refractive index of long period fiber grating were analyzed by using the coupled-mode theory, the relationship between the content of diesel oil and the long period fiber grating’s resonant wavelength and transmitted intensity was obtained. The result shows that when the diesel oil of the mixed oil increases, the long period fiber grating resonance wavelength blue-shifts. And when the concentration of diesel oil reaches a certain concentration that the refractive index of the solution is equal to the cladding refractive index, the resonance wavelength will shift to the maximum. As the concentration of diesel changes 1%, the average shifts of resonance wavelength reaches 0.622 7 nm. As the diesel oil increases sequentially, the refractive index of mixed oil exceeds the cladding refractive index, and the resonant wavelength does not change basically, the shape changes greatly with the bandwidth decreasing and the peak loss increasing. And with the concentration of diesel oil increasing unceasingly, the peak loss increase and bandwidth diminishes. As the concentration of diesel changes 1%, the peak loss reaches 0.154 6 dB. So the long period fiber grating has a potential application prospect in the detection of mixed fuel concentration.