Linking Distributed and Integrated Fiber‐Optic Sensing

Abstract

Distributed Acoustic Sensing (DAS) has become a popular method of observing seismic wavefields: backscattered pulses of light reveal strains or strain rates at any location along a fiber‐optic cable. In contrast, a few newer systems transmit light through a cable and collect integrated phase delays over the entire cable, such as the Microwave Frequency Fiber Interferometer (MFFI). These integrated systems can be deployed over significantly longer distances, may be used in conjunction with live telecommunications, and can be significantly cheaper. However, they provide only a single time series representing strain over the entire length of the fiber. This work discusses theoretically how a distributed and integrated system can be quantitatively compared, and we note that the sensitivity depends strongly on points of curvature. Importantly, this work presents the first results of a quantitative, head‐to‐head comparison of a DAS and the integrated MFFI system using pre‐existing telecommunications fibers in Athens, Greece.

A simple algorithm for optimal design in distributed fibre-optic sensing

“…Variations of the Kangerlussuaq may be used for OED with fibre-optic sensing technologies that are not based on DAS. This includes, for instance, transmission fibre-optics systems that are characterized by a position-dependent measurement sensitivity that is controlled by local cable curvature (Marra et al 2018;Mecozzi et al 2021;Bowden et al 2022;Bogris et al 2022;Fichtner et al 2022a). High-curvature segments along the cable thereby mimic a distributed sensing system that should be optimally designed in order to maximize resolution of Earth structure or earthquake source parameters.…”

Dual wavelength microwave frequency fiber interferometer system for distributed localization based on time delay estimation

“…Compared with common optical fiber sensors based on light wave interference or light wave reflection such as φ-OTDR, the MFFI have the advantages of low cost and insensitive to factors such as loss and dispersion in the optical fiber link, which makes it suitable for low frequency sensing applications such as submarine seismic monitoring. However, the MFFI can only achieve integrated sensing [3], which means the information of external disturbances at all locations of the entire optical fiber link can only be monitored together, so that the MFFI cannot achieve distributed localization of disturbances, which limits its practicality.…”

Long-range fiber-optic earthquake sensing by active phase noise cancellation

“…Adopting a conceptually similar approach, a microwave frequency fiber interferometer (MFFI) has been developed at a fraction of the cost of commercial DAS units 19 , making this technology attractive for environmental and natural hazard applications in low-income countries. A side-by-side comparison of DAS and MFFI highlighted the potential of the latter for quantitative science 20 . While technologies based on phase transmission only provide spatially integrated, instead of distributed, deformation measurements, some level of spatial resolution can be achieved either through the use of repeaters between fiber segments 21 or a time-dependent analysis of the signals 22 .…”