预制棒POVD工艺中等离子体温度的光谱测量

Spectroscopic Measurement of Plasma Temperature in the POVD Process for Prefabricated Rods

摘要:

等离子体外部气相沉积法(Plasma-Outside-Vapor-Deposition,POVD)能够制造出高质量的光纤预制棒,其中高频感应等离子体炬的温度诊断是确保光纤预制棒质量和性能的关键环节。然而在实际测量环境中,由于等离子体物理过程的复杂性和不稳定性,温度诊断的一致性和准确性问题普遍存在。文章基于非接触式发射光谱诊断技术,针对POVD工艺中等离子体光谱数据绘制Boltzmann图,拟合计算出等离子体温度。为了得到准确性高的电子温度计算结果,文章提出了一套适用于各阶段各元素的等离子体光谱谱线筛选标准。经过谱线筛选后的测温结果,各阶段拟合线性度均优于0.96,同时不同积分时间下测温结果的变异系数CV也从原先的20.74%降低到了5.55%以下。由此证明了文章提出的等离子体光谱谱线筛选标准能够很好地改善等离子体温度诊断中存在的一致性和准确性问题。

关键词:光纤预制棒;等离子体外部气相沉积法;光谱;等离子体温度诊断;一致性

Abstract:

The Plasma-Outside-Vapor-Deposition (POVD) technique is capable of manufacturing high-quality optical fiber preforms, with the temperature diagnosis of the high-frequency induction plasma torch being a crucial aspect in ensuring the quality and performance of the optical fiber preforms. However, in practical measurement environments, due to the complexity and instability of the plasma physical processes, consistency and accuracy issues are commonly encountered in temperature diagnosis. This study employs a non-contact emission spectroscopy diagnostic technique to construct Boltzmann plots from the plasma spectral data in the POVD process, thereby calculating the plasma temperature through fitting. To obtain highly accurate electron temperature calculation results, a set of plasma spectral line selection criteria applicable to various stages and elements has been proposed. After spectral line screening, the fitting linearity in each stage is improved to be better than 0.96, and the coefficient of variation (CV) of the temperature measurement results under different integration times is reduced from the original 20.74% to below 5.55%. These results demonstrate that the proposed plasma spectral line selection criteria can effectively address the consistency and accuracy issues in plasma temperature diagnosis.

Key words:Fiber optic preforms; POVD; Spectroscopy; Plasma temperature diagnostics; Consistency