基于耦合模和材料力学理论，研究了四芯光纤布拉格(Bragg)光栅(FBG)的横向力传感特性与横向力大小、方向及光纤包层外径之间的关系。在横向力作用下，4个纤芯的布拉格光栅的反射谱分裂成两个波峰，谐振波长及两峰间隔均与横向力大小成正比，却随着横向力加载角度的增大而减小；处于两个相垂直的径向上的光纤光栅的波峰分裂比值与横向力大小无关，只与横向力加载方向有关。在保证光纤归一化频率不变的前提下，谐振波长与波峰分裂均随光纤外径的减小而增加，但增加的程度会随横向力加载角度而变化。

Based on coupled-mode theory and mechanics of materials, the four-core fiber Bragg gratings (F-CFBG) transverse force sensing rules according to transverse load, direction and fiber outer diameter were studied. The F-CFBG reflection spectrum split into two main peaks under transverse load. The resonant wavelength changes and the space between those two peaks are proportional with the applied transverse force magnitude, but decrease as the transverse orientation increases. The ratio of the peak splitting between two cores at 90° separation only lie on the orientation of transverse. The numerical analysis of F-CFBG wavelength shift with different outer diameters was also presented respectively. On condition that normalized frequency keeps constant, the wavelength change and the space between those two peaks increase as the fiber outer diameter decreases, but the increase degree lie on the transverse orientation.