起偏角对保偏光纤中光波偏振度的影响

Influence of starting angle on light's degree of polarization in polarization maintaining fiber

实际应用中,入射到保偏光纤的光波通常是准单色光。当入射光的偏振方向与保偏光纤本征轴未对准时,光波在保偏光纤中传播时的偏振度会发生变化。利用部分相干理论分析了准单色偏振光和部分偏振光在保偏光纤中传播时偏振度随起偏角和传播距离的变化情况。实验研究了部分偏振光的偏振度随起偏角变化的规律。研究结果表明:传播距离在厘米量级内时,偏振度随传播距离的变化较明显,对于一般的长距离传输而言,传播距离对偏振度的影响可以忽略;与传播距离相比,起偏角对偏振度的影响较大,为了使偏振度的相对变化量小于0.01%,起偏角必须控制在0.405°以内。

In practical application,the light injected to polarization maintaining fiber（PMF） is typically quasi-monochromatic.When the polarization direction of the incident light and the birefringence axes of the fiber were misaligned,the degree of polarization（DOP） would be changed in transmission process.Using partial coherence theory,the dependence of polarized and partially polarized light＇s DOP on the starting angle and transmission distance in PMF were analyzed theoretically.And some experiments were done to study the dependence of partially polarized light＇s DOP on the starting angle. The results show that,if the transmission distance is in centimeter magnitude, the influence on DOP is great.To normal long distance transmission,its influence could be neglected.Compared with the transmission distance,DOP varies greatly with the starting angle.To achieve the relative change of DOP less than 0.01%,the starting angle must be smaller than 0.405°.