In this letter, we present the design of two-cascaded cavities, used as sensing head, for improving the performance of a fiber refractometer. The sensing system makes use of the Coherent-OFDR technique. Using the proposed method, only 15 % length of the sensing signal is used to calculate the refractive index (RI) of the sample under test. Due to reduction of the scanning range used for RI calculation, the nonlinearity effect in wavelength scanning is also reduced. In order to optimize the length of the sensing signal, the proposed design considers the ratio of length of each cavity. We describe, step-by-step, the design parameters; and the experiments to demonstrate the effectiveness of the proposed method. In the experiments, a resolution of 10−6 is reported.

中文翻译：

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基于C-OFDR的降低光纤折射仪非线性效应的级联腔设计

在这封信中，我们介绍了用作传感头的两个级联腔的设计，以提高光纤折射计的性能。传感系统使用相干-OFDR 技术。使用所提出的方法，仅使用 15% 的传感信号长度来计算被测样品的折射率 (RI)。由于减少了用于 RI 计算的扫描范围，波长扫描中的非线性效应也减少了。为了优化传感信号的长度，所提出的设计考虑了每个腔的长度比。我们逐步描述设计参数；和实验证明了所提出方法的有效性。在实验中，报告了 10-6 的分辨率。