随着光纤到户网络的逐渐普及，弯曲不敏感光纤受到了越来越多的关注。对下陷层辅助弯曲不敏感光纤进行了系统的研究。在带有下陷层的弯曲不敏感光纤中，下陷层的折射率差、下陷层的宽度以及下陷层至芯层的距离是影响弯曲损耗的三个重要参数。结合上述三个参数，系统研究了光纤半径以及涂覆层折射率对弯曲损耗的影响。研究表明，通过改变光纤半径可以有效降低弯曲损耗；在特定的弯曲半径下，当涂覆层折射率增大时可以有效减小光纤的弯曲损耗。这些结论对弯曲不敏感光纤的设计及制造具有指导意义。

With the development of fiber-to-the-home (FTTH) network, bend-insensitive fiber (BIF) has attracted more and more attention. We focus on bending losses of the trench-assisted bend-insensitive optical fiber. For the trench-assisted bend-insensitive fiber, the refractive index difference of trench, the width of trench and the distance between the core and trench are three important parameters which could influence the bending loss. Combining the three parameters, we investigate the impact of fiber radius and refractive index of the coating layer on the bending losses. It is shown that: bending losses can be effectively reduced by changing the radius of the fiber; with refractive index of the coating layer increasing, the bending losses of the fiber could be effectively reduced for certain bending radius. The conclusion is of significance for designing and manufacturing of bend-insensitive fibers.