This paper proposes a fiber length matching method that reduces the influence of Fresnel reflection in a hybrid fiber resonator for the resonant fiber optic gyroscope (RFOG). A transfer model of the fused points inside and outside the fiber resonator is first built. Using the transfer model, we find that when the optical path ratio of the photonic bandgap fiber (PBF) is half of the entire fiber ring, the secondary resonant frequency points caused by Fresnel reflection coincide with the main resonant frequency points of the resonator, and the resonant depth becomes equal. The simulation result of the resonance curve demonstrates this theory. To validate our deduction, two hybrid resonators are obtained with PBF and polarization-maintaining fiber (PMF). The optical path ratio of one resonator is 0.5, and the other is approximately 0.2. The results show that after the fiber length matching, the resonance depth difference of the resonator is less than 1.8%, which is the best reported index of a fused PBF fiber resonator to our knowledge and 24.9% less than that of the other resonator. The experimental result also shows that the total loss of the two PBF-PMF fused points is less than 1.3 dB. Our scheme effectively reduces the effect of the Fresnel reflection at the fusing point in the PBF-PMF resonator, which is expected to achieve accurate resonance frequency detection of the RFOG.

中文翻译：

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减少 RFOG 混合 PBF-PMF 谐振器中的菲涅耳反射效应

本文提出了一种光纤长度匹配方法，该方法可减少用于谐振光纤陀螺仪 (RFOG) 的混合光纤谐振器中菲涅耳反射的影响。首先建立了光纤谐振腔内外融合点的传递模型。使用传递模型，我们发现当光子带隙光纤（PBF）的光路比为整个光纤环的一半时，菲涅耳反射引起的次级谐振频率点与谐振腔的主要谐振频率点重合，并且共振深度变得相等。谐振曲线的仿真结果证明了这一理论。为了验证我们的推论，使用 PBF 和保偏光纤 (PMF) 获得了两个混合谐振器。一个谐振腔的光路比为 0.5，另一个约为 0.2。结果表明，在光纤长度匹配后，谐振器的谐振深度差小于1.8%，这是据我们所知的熔合PBF光纤谐振器的最佳报道指标，比其他谐振器低24.9%。实验结果还表明，两个PBF-PMF融合点的总损耗小于1.3 dB。我们的方案有效地降低了PBF-PMF谐振器熔点处菲涅耳反射的影响，有望实现RFOG的准确谐振频率检测。实验结果还表明，两个PBF-PMF融合点的总损耗小于1.3 dB。我们的方案有效地降低了PBF-PMF谐振器熔点处菲涅耳反射的影响，有望实现RFOG的准确谐振频率检测。实验结果还表明，两个PBF-PMF融合点的总损耗小于1.3 dB。我们的方案有效地降低了PBF-PMF谐振器熔点处菲涅耳反射的影响，有望实现RFOG的准确谐振频率检测。