The impact of surface-polish on the angular and wavelength dependence of fiber focal ratio degradation
The impact of surface-polish on the angular and wavelength dependence of fiber focal ratio degradation
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DOI：
10.1117/12.926568
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发表时间：
2012-08
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影响因子：
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通讯作者：
A. Eigenbrot;M. Bershady;C. M. Wood
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作者：
A. Eigenbrot;M. Bershady;C. M. Wood
我们测量了多模光纤焦距比退化（FRD）和吞吐量如何随光纤表面抛光程度（从60微米到0.5微米）而变化。测量使用全光束和激光注入方法，波长在0.4和0.8微米之间，17米长的Polymicro FBP 300和400 μm芯光纤。全光束注入探测f/3和f/13.5之间的输入焦距比，而激光注入允许我们在高达17度的离散注入角（f/1.6边缘光线）隔离FRD。我们发现：（1）FRD效应随着磨料尺寸的减小而减小，当磨料尺寸大于5 μm时，光束质量的最大增益出现;（2）总吞吐量随着磨料尺寸的减小而增加，在790 nm处，最精细的抛光水平达到90%;（3）对于较粗的抛光磨料，在较红的波长处，总吞吐量较高，表明表面散射是损失的主要来源。我们还量化的角度依赖的FRD作为抛光水平的函数。我们的研究结果表明，一个普遍采用的微弯曲模型FRD是一个贫穷的描述所观察到的现象。
We present measurements of how multimode fiber focal-ratio degradation (FRD) and throughput vary with levels of fiber surface polish from 60 to 0.5 micron grit. Measurements used full-beam and laser injection methods at wavelengths between 0.4 and 0.8 microns on 17 meter lengths of Polymicro FBP 300 and 400 μm core fiber. Full-beam injection probed input focal-ratios between f/3 and f/13.5, while laser injection allowed us to isolate FRD at discrete injection angles up to 17 degrees (f/1.6 marginal ray). We find (1) FRD effects decrease as grit size decreases, with the largest gains in beam quality occurring at grit sizes above 5 μm; (2) total throughput increases as grit size decreases, reaching 90% at 790 nm with the finest polishing levels; (3) total throughput is higher at redder wavelengths for coarser polishing grit, indicating surface-scattering as the primary source of loss. We also quantify the angular dependence of FRD as a function of polishing level. Our results indicate that a commonly adopted micro-bending model for FRD is a poor descriptor of the observed phenomenon.