It is demonstrated that in this paper a peanut shaped structure cascaded with up-taper fiber structure can realize the inter mode interference between the Erbium doped fiber (EDF) core mode and cladding modes in fiber ring laser (FRL). A simple and inexpensive Mach–Zehnder interferometer (MZI) based on this structure is proposed. Shown from experimental results, the optical intensity of the core mode can be coupled into the cladding modes in the first peanut-shaped structure. Then, the light in the cladding modes can be recoupled into the core mode in the up-taper structure. A high-quality interference spectrum with a signal to noise ratio about 50 dB was observed. Besides, the structure exhibits good mechanical stability when compared to MZIs based on taper or offset structure. The temperature sensitivity of the FRL sensor is 301 pm/°C and the RI sensitivity is 156 nm/RIU. This kind of MZI will have potential applications in remote sensing technique and the development of life and health.

中文翻译：

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光纤环形激光器中基于Er掺杂向上锥度和花生形光纤结构的光纤内马赫-曾德尔干涉仪

证明了在本文中，花生形结构与向上锥形光纤结构级联可以实现光纤环形激光器（FRL）中掺铒光纤（EDF）芯模和包层模之间的模间干涉。提出了一种基于这种结构的简单且廉价的马赫-曾德干涉仪 (MZI)。实验结果表明，在第一个花生形结构中，纤芯模式的光强可以耦合到包层模式中。然后，包层模式中的光可以重新耦合到向上锥形结构中的纤芯模式中。观察到信噪比约为 50 dB 的高质量干扰频谱。此外，与基于锥度或偏移结构的 MZI 相比，该结构表现出良好的机械稳定性。FRL 传感器的温度灵敏度为 301 pm/°C，RI 灵敏度为 156 nm/RIU。这种MZI将在遥感技术和生命健康发展方面具有潜在的应用价值。