Relative contributions of scattering, diffraction and modal diffusion to focal ratio degradation in optical fibres
Relative contributions of scattering, diffraction and modal diffusion to focal ratio degradation in optical fibres
复制标题
散射、衍射和模态扩散对光纤焦比下降的相对贡献
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
R. Haynes
中科院分区：
文献类型：
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作者：
D. Haynes;M. Withford;J. Dawes;J. Lawrence;R. Haynes
在采用多模光纤的天文仪器中，焦比衰减（FRD）是造成光损失的主要原因。我们提出了一个强大的诊断模型，该模型独特地量化了多模光纤中FRD的各种来源。有三种主要现象可以导致FRD：散射、衍射和模态扩散。我们提出了一个Voigt FRD模型，其中衍射和模态扩散由高斯分量模拟，端面散射由洛伦兹分量模拟。Voigt FRD模型可以反卷积成高斯分量和洛伦兹分量，并用于分析三个主要分量的贡献。我们使用Voigt FRD模型来分析现代天文级纤维的FRD在(i)端面表面粗糙度，（ii）波长，（iii）纤维长度和（iv）外部纤维应力方面的变化。我们观察到的FRD升高主要是由于外部因素造成的，即纤维末端效应，如表面粗糙度、亚表面损伤和环氧树脂、卡箍和纤维电缆设计引起的环境诱导微弯曲。Voigt FRD模型有许多应用，例如作为当前光纤仪器显示FRD升高的诊断工具，作为光纤制造和光纤电缆组装的质量控制方法，以及作为表征新光纤技术的研究和开发工具。
Focal ratio degradation (FRD) is a major contributor to light loss in astronomical instruments employing multimode optical fibres. We present a powerful diagnostic model that uniquely quantifies the various sources of FRD in multimode fibres. There are three main phenomena that can contribute to FRD: scattering, diffraction and modal diffusion. We propose a Voigt FRD model where the diffraction and modal diffusion are modelled by the Gaussian component and the end-face scattering is modelled by the Lorentzian component. The Voigt FRD model can be deconvolved into its Gaussian and Lorentzian components and used to analyse the contribution of each of the three major components. We used the Voigt FRD model to analyse the FRD of modern astronomical grade fibre for variations in (i) end-face surface roughness, (ii) wavelength, (iii) fibre length and (iv) external fibre stress. The elevated FRD we observed was mostly due to external factors, i.e. fibre end effects such as surface roughness, subsurface damage and environmentally induced microbending caused by the epoxy, ferrules and fibre cable design. The Voigt FRD model has numerous applications such as a diagnostic tool for current fibre instrumentation that show elevated FRD, as a quality control method for fibre manufacture and fibre cable assembly and as a research and development tool for the characterization of new fibre technologies.