Microwave frequency dissemination systems as sensitive and low-cost interferometers for earthquake detection on commercially deployed fiber cables

Bogris, Adonis; Simos, Christos; Simos, Hercules; Νίκας, Θωμάς; Melis, Νikolaos S.; Lentas, Konstantinos; Mesaritakis, Charis; Chochliouros, Ioannis P.; Lessi, Christina

doi:10.48550/arxiv.2111.02957

Cited by 3 publications

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“…This section focuses on the interpretation of a strain wavefield, as measured by a system based on transmitted phase changes, including those of Marra et al (2018) and Bogris et al (2021Bogris et al ( , 2022. We do not focus on the technical or engineering details, and instead analyse how a seismic wavefield is represented and interpreted.…”

Section: Theoretical Background Of Phase Transmission Fibre Opticsmentioning

confidence: 99%

“…10), we see that we can directly compare a DAS system to the MFFI output. In September and October of 2021, we operated a Silixa iDAS interrogator alongside the system described by Bogris et al (2021Bogris et al ( , 2022. Both systems used pre-existing telecommunications fiber in collaboration with the Hellenic Telecommunications Organisation (OTE), and the work was completed with assistance from the National Observatory of Athens.…”

Section: Experimental Comparison Of Integrated and Distributed Sensingmentioning

confidence: 99%

“…Some authors have successfully measured polarization changes accumulated along the entire fibers (Mecozzi et al, 2021;Zhan et al, 2021), while others might measure changes in phase (Marra et al, 2018). Recently, Bogris et al (2021Bogris et al ( , 2022) installed one such system in a suburban region of Athens, using pre-existing telecommunications fiber. Their particular system relies on the interferometric use of microwaverange frequencies -signals sent along the fiber and back in a closed loop are compared to what was sent and phase differences are measured.…”

Section: Introductionmentioning

confidence: 99%

“…In September and October of 2021, we ran a Silixa iDAS interrogator alongside the MFFI system of Bogris et al (2021Bogris et al ( , 2022 in northern Athens, Greece, in collaboration with the Hellenic Telecommunications Organisation (in Greek: OTE). A number of earthquakes were observed, including both local-and regional-scale events.…”

Section: Introductionmentioning

confidence: 99%

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Linking distributed and integrated fiber-optic sensing

Bowden,

Fichtner,

Nikas

et al. 2022

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Section: Theoretical Background Of Phase Transmission Fibre Opticsmentioning

confidence: 99%

Section: Experimental Comparison Of Integrated and Distributed Sensingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Linking distributed and integrated fiber-optic sensing

Bowden,

Fichtner,

Nikas

et al. 2022

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“…Emerging alternative systems overcome this limitation by measuring deformation-induced changes in the phase (Marra et al, 2018;Bogris et al, 2021Bogris et al, , 2022Bowden et al, 2022) or the polarisation (Mecozzi et al, 2021) of transmitted laser light. The ability of transmission-based systems to achieve interrogation distances of hundreds or thousands of kilometres opens new opportunities to investigate seismic activity and Earth structure in remote regions where conventional seismic instrumentation is sparse.…”

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Introduction to phase transmission fibre-optic sensing of seismic waves

Fichtner¹,

Bogris²,

Νίκας³

et al. 2022

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This manuscript is concerned with phase changes of signals transmitted through deforming optical fibres. As a first result, it establishes an exact relation between observable phase changes and the deformation tensor along the fibre. This relation is non-linear, and it includes effects related to both local changes in fibre length and deformation-induced changes of the local speed of light or refractive index.In seismic applications, where the norm of the earthquake-induced deformation tensor is orders of magnitude smaller than 1, a useful first-order relation can be derived. It simply connects phase changes to an integral over in-line strain along the fibre times the local refractive index. Under the assumption that spatial variations of the refractive index are fast compared to the seismic wavelength, this permits a direct synthesis of phase change measurements from distributed strain measurements, for instance, from Distributed Acoustic Sensing (DAS).A more detailed analysis of the first-order relation reveals that a perfectly straight fibre would produce zero phase change measurements, unless deformation was sufficiently widespread to affect the starting and end points of the fibre. If this condition is not met, non-zero measurements can only result from curvature of the fibre or from a heterogeneous distribution of the refractive index. Segments of the fibre that are strongly curved generally make larger contributions to the observed phase change.Second-or higher-order effects, not captured by the first-order relation, may be observable in specific scenarios, including deformation exactly perpendicular to the fibre orientation. They are associated with a frequency content that is higher than that of the underlying deformation field. Though higher-order effects may be realised in controlled laboratory settings, they are unlikely to occur in seismic experiments where fibre geometries are irregular and waves asymptotically propagate in all directions with all possible polarisations, as a consequence of 3-D heterogeneity

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Linking Distributed and Integrated Fiber‐Optic Sensing

Bowden

Fichtner

Νίκας

et al. 2022

Geophysical Research Letters

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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.

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Microwave frequency dissemination systems as sensitive and low-cost interferometers for earthquake detection on commercially deployed fiber cables

Cited by 3 publications

References 0 publications

Linking distributed and integrated fiber-optic sensing

Linking distributed and integrated fiber-optic sensing

Introduction to phase transmission fibre-optic sensing of seismic waves

Linking Distributed and Integrated Fiber‐Optic Sensing

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