Signal-to-Noise Ratio of Brillouin Grating Measurement with Micrometer-Resolution Optical Low Coherence Reflectometry
Signal-to-Noise Ratio of Brillouin Grating Measurement with Micrometer-Resolution Optical Low Coherence Reflectometry
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DOI：
10.3390/s20030936
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发表时间：
2020-02
期刊：
影响因子：
--
通讯作者：
K. Takada;S. Satoh;A. Kawakami
中科院分区：
文献类型：
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作者：
K. Takada;S. Satoh;A. Kawakami
信号相关的散斑噪声是使用微米分辨率光学低相干反射计 (OLCR) 进行布里渊光栅测量时的主要噪声。该噪声是由斯托克斯信号与通过平方律检测泄漏的泵浦光引起的拍频噪声相互作用产生的。计算得出的信噪比 (SNR) 与动态范围 (DR) 的平方根成正比，动态范围 (DR) 是由斯托克斯信号幅度与拍频噪声方差之比定义的。计算表明，即使我们在对数尺度上实现了 20 dB 的 DR，在线性尺度上的 SNR 值也仅为 7，并且检测到的信号相对于平均水平往往会波动超过 ±14%。通过将进入平衡混频器的泵浦光功率衰减 55 dB，我们实现了 24 的 SNR，这一成功使我们能够测量配对光纤连接器和具有微米分辨率的 3 dB 熔融光纤耦合器的布里渊频谱分布，作为 OLCR 诊断的示例。
Signal-dependent speckle-like noise was the dominant noise in a Brillouin grating measurement with micrometer-resolution optical low coherence reflectometry (OLCR). The noise was produced by the interaction of a Stokes signal with beat noise caused by a leaked pump light via square-law detection. The resultant signal-to-noise ratio (SNR) was calculated and found to be proportional to the square root of the dynamic range (DR) defined by the ratio of the Stokes signal magnitude to the variance of the beat noise. The calculation showed that even when we achieved a DR of 20 dB on a logarithmic scale, the SNR value was only 7 on a linear scale and the detected signal tended to fluctuate over ±14% with respect to the mean level. We achieved an SNR of 24 by attenuating the pump light power entering the balanced mixer by 55 dB, and this success enabled us to measure the Brillouin spectrum distributions of mated fiber connectors and a 3-dB fused fiber coupler with a micrometer resolution as examples of OLCR diagnosis.