Abstract
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.
Highlights
Passive fiber-optic sensors such as fiber Bragg gratings (FBG) and fiber Fabry-Perot Interferometers (FFPI) have demonstrated tremendous potential to achieve ultrahigh-resolution (UHR) optical sensing [1], [2]
A nominal, noise-limited strain resolution of 800 fε/ÝHz has been achieved within 1–100 Hz
Strain resolution further improves to 75 fε/ÝHz at 1 kHz, 60 fε/ÝHz at 2 kHz and 40 fε/ÝHz at 23 kHz, demonstrating better resolutions than proven techniques such as π -phase-shifted and slow-light fiber Bragg gratings
Summary
Passive fiber-optic sensors such as fiber Bragg gratings (FBG) and fiber Fabry-Perot Interferometers (FFPI) have demonstrated tremendous potential to achieve ultrahigh-resolution (UHR) optical sensing [1], [2]. When external disturbance (e.g., longitudinal strain or temperature fluctuation) is applied, internal parameters such as grating period, cavity length and refractive index are subject to a change. This in turn triggers a detuning of the spectral features associated with these parameters [1]. For an FBG sensor, the Bragg reflection peak is the characteristic spectral marker [3], whereas for an FFPI, the resonance transmission peak typically serves as the indicator for spectral changes [4]. The main goal for improving sensing resolution is to create spectral features as narrow
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