Ultrahigh-Resolution Fiber-Optic Sensing Based on High-Finesse, Meter-Long Fiber Fabry-Perot Resonators

Ultrahigh-resolution fiber-optic sensing has found a wide range of potential applications. However, the techniques reported so far are all based on highly specialized fiber structures and interrogation lasers, which are not widely available. In this paper, we report the demonstration of ultrahigh strain resolutions using only off-the-shelf commercial components. Our method leverages the high wavelength discrimination of long, high-finesse fiber Fabry-Perot interferometers (FFPI), using two 1 m-long FFPIs, one as the sensor and the other as a frequency reference. By locking the interrogation laser to the reference interferometer, which is co-packaged with the sensor interferometer, large, environment-induced sensing background is removed. This allows the laser to reliably probe the strains applied on the sensor with very high resolutions. A nominal, noise-limited strain resolution of 800 fϵ/√Hz has been achieved within 1–100 Hz. Strain resolution further improves to 75 fϵ/√Hz at 1 kHz, 60 fϵ/√Hz at 2 kHz and 40 fϵ/√Hz at 23 kHz, demonstrating better resolutions than proven techniques such as π-phase-shifted and slow-light fiber Bragg gratings. The work lays out a cost-effective scheme to achieve ultrahigh-resolution fiber-optic sensing.