多孔光纤偏振拍长宽带稳定性的优化设计

Optimized design for birefringent holey fiber with wideband stable beat-length

为制作宽带稳定的光纤偏振器件,设计了一种偏振拍长对波长变化不敏感的多孔光纤.将包层气孔呈菱形阵列分布、纤芯附近有一对大气孔的多孔光纤在两个正交方向上进行横向压缩或伸展,以扩大模式双折射随波长同步线性变化的波长区间.应用全矢量有限差分光束传播法,分析了不同伸缩因子对双折射和偏振拍长色散特性的影响.研究结果表明:横向伸缩形变可以有效地抑制菱形晶格多孔光纤双折射的非线性变化,使偏振拍长在较宽的波长范围内具有较好的稳定性.通过优化设计,这种菱形晶格多孔光纤在1.0μm～2.0μm波长范围内,偏振拍长在180 mm～185 mm之间变化,相对变化率约为3%,工作带宽达到800 nm,可以同时覆盖1 310 nm和1 550 nm两个常用通信波长窗口,较为适合用于制作宽带光纤波片.

In order to make fiber polarization components and devices, a new holey fiber insensitive to wavelength is designed. The cross-section of the holey fiber, with elliptical air holes cladding array and a pair of large holes near the core, was squeezed and expanded in orthogonal directions in order to reach the wavelength range in which birefringenee changes synchronously and linearly with wavelength. The impact of lateral deformation on birefringence and polarization beat-length dispersion characteristics of the diamond lattice birefringent holey fiber was studied through full-vector finite difference beam propagation method. The results demonstrate that lateral deformation can effectively suppress the nonlinear change ofbirefrlngence in the holey fiber. The polarization beat- length remains stable in a wider wavelength range. By optimizing the design, the polarization beat-length changes in the range of 180-185mm and the relative variation of polarization beat-length is about 3%. The work bandwidth is up to 800nm in 1.0-2.0μm covering both 1310nm and 1550nm wavelength windows. This fiber is suitable for making wideband fiber-optic wave-plate.