Abstract We propose and numerically investigate a fiber-optic sensor comprised by core-offset splicing up to 20 equal-length single-mode fiber (SMF) segments, which is used for the high-sensitivity refractometric sensing owing to the open cavities with much light propagating outside the optical fiber. The emergence of high-order modes in the silica cladding and air enhances the multi-mode interference, therefore improving the device sensitivity. Because of the small core-offset distance between fiber segments and suitable fiber segment length, enhanced light scattering reduces the degeneracy and overcomes free-spectrum-range limitation in that case of Fabry–Perot interferometer (FPI) with equal fiber segments, resulting in the large wavelength tuning range. Furthermore, silver (Ag) particles, Ag rod and Ag microsphere placed on the core-offset region, respectively, further enhance the light intensity outside the fiber owing to the reconfiguration and refocusing of optical light after the silver particles, then further improving the sensitivity of refractometric sensing. Up to 1078 nm per refractive index unit (nm/RIU) could be obtained based on 6 μ m -diameter Ag microsphere-assisted fiber-optic sensor with 10 fiber segments.

中文翻译：

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基于银粒子辅助纤芯偏移熔融光纤段的高灵敏度折光传感

摘要 我们提出并数值研究了一种由纤芯偏移拼接组成的光纤传感器，该传感器由多达 20 个等长单模光纤 (SMF) 段组成，由于具有大量光的开放腔，该传感器用于高灵敏度折射测量。在光纤外传播。二氧化硅包层和空气中高阶模式的出现增强了多模干扰，从而提高了器件灵敏度。由于光纤段之间的纤芯偏移距离较小且光纤段长度合适，增强的光散射降低了简并性并克服了在具有相等光纤段的 Fabry-Perot 干涉仪 (FPI) 情况下的自由光谱范围限制，导致波长调谐范围大。此外，银 (Ag) 颗粒，Ag棒和Ag微球分别放置在纤芯偏移区域，由于银颗粒后光学光的重新配置和重新聚焦，进一步增强了光纤外的光强度，从而进一步提高了折光传感的灵敏度。基于具有 10 个光纤段的 6 μ m 直径 Ag 微球辅助光纤传感器，可以获得高达 1078 nm 每个折射率单位 (nm/RIU)。