High-resolution strain sensing based on long, high-finesse fiber Fabry–Perot interferometers (FFPIs) has been demonstrated with a special focus on the infrasonic frequency range. A novel dual-FFPI scheme allows the large environment-induced background at low frequencies to be suppressed, permitting high strain resolution limited only by excess electronic noise. Noise-equivalent strain resolution of ${{257}}\;{{{\rm p}\unicode{x03B5} /}}\surd {\rm{Hz}}$ has been achieved at 6 mHz, and the resolution improves to ${\sim}{{200}}\;{{{\rm f}\unicode{x03B5} /}}\surd {\rm{Hz}}$ between 4–20 Hz. Without the use of any additional optical frequency references and with only off-the shelf commercial components, these resolutions are much better than most in the prior reports. Especially, an improvement of a factor of 1.8 is achieved in comparison with the highest resolution reported so far near 5 Hz. The limiting factors of the current scheme have been analyzed in detail, and the application prospects have been demonstrated using an acoustic transducer. The work lays out the potential of using long FFPIs with high finesse for high-resolution fiber-optic sensing in the infrasonic frequency range.

中文翻译：

---

皮亚微米级分辨率光纤传感，亚声频率低至10 mHz

基于长而精细的光纤法布里-珀罗干涉仪（FFPI）的高分辨率应变传感已经得到了证明，并且特别关注次声频率范围。一种新颖的双重FFPI方案可以抑制低频下由大环境引起的背景，从而允许仅由过量电子噪声限制的高应变分辨率。$ {{257}} \; {{{\ rm p} \ unicode {x03B5} /}} \ surd {\ rm {Hz}} $的等效噪声应变分辨率已达到6 mHz，且分辨率提高了到$ {\ sim} {{200}} \ ;; {{{\ rm f} \ unicode {x03B5} /}} \ surd {\ rm {Hz}} $在4–20 Hz之间。在不使用任何其他光学频率参考并且仅使用现成的商业组件的情况下，这些分辨率比以前的报告中的大多数要好得多。特别是，与迄今报道的接近5 Hz的最高分辨率相比，可以提高1.8倍。详细分析了当前方案的局限性，并通过声换能器证明了其应用前景。这项工作为在次声频率范围内高分辨率光纤传感使用高精细的长FFPI提供了可能。