The use of single-mode fibers (SMFs) to illuminate radial velocity (RV) spectrographs shows promise to achieve extremely precise Doppler measurements. Due to their small core diameter, SMFs only propagate a single spatial mode which allows for diffraction-limited optical performance while simultaneously eliminating fiber modal noise. The single spatial mode however consists of two orthogonal polarization modes. In circular core fiber with a non-isotropic refractive index profile or asymmetries in the cross-sectional geometry, the two polarization modes propagate with different relative speeds inducing birefringence. Conditions at a telescope observatory will subject the fiber to mechanical (bending and twisting) and thermal stresses, inducing birefringence that varies in time. The interaction of variable birefringence combined with with polarization sensitive optics, such as diffraction gratings, results in an intensity modulation that causes unwanted Doppler shifts via “polariz...

中文翻译：

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减轻单模光纤光谱仪中的偏振效应

使用单模光纤（SMF）照亮径向速度（RV）光谱仪表明有望实现极其精确的多普勒测量。由于它们的纤芯直径小，SMF仅传播单一空间模态，从而允许衍射受限的光学性能，同时消除了光纤模态噪声。但是，单个空间模式由两个正交极化模式组成。在具有非各向同性折射率分布或横截面几何形状不对称的圆形芯光纤中，两种偏振模式以引起双折射的不同相对速度传播。望远镜天文台的条件将使光纤承受机械（弯曲和扭曲）和热应力，从而导致双折射随时间变化。