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Distributed Environmental Sensing Using Trans-Oceanic Subsea Cables

We present a distributed fiber optic sensing (DFOS) prototype capable of measurements beyond the first repeater of subsea cables. The cable spans approximately 6,400 km and includes more than 80 optical repeaters. Our system is capable of distributed measurements of both phase and polarization of the backscattered signal, including the Rayleigh backscattering from the silica fiber and point reflections from fiber Bragg gratings (FBGs) present within the optical repeaters. Each point along the cable is measured in real-time, with zero dead time and covering a frequency range from mHz to kHz. This measurement spans all degrees of freedom supported by the fiber and therefore completely characterizes its linear response over the measurement bandwidth.

During a 1 month measurement period, all world-wide earthquakes with >6 magnitude were detected. Here we present a detailed analysis of the measured signatures from two earthquakes and ocean swells. The first event is a 6.3 magnitude earthquake with an epicenter in California, while the second event is a 7.1 magnitude event located in Indonesia. The recorded signatures from our about 80 points along the ocean floor are compared with data from the two available seismic stations in the North Atlantic ocean. Our measurement results show good quantitative agreement with the waveforms recorded by the land-based seismic stations. In addition, we show real-time tracking of the seismic waves as they propagate along the cable and use this to determine their relative speed. This technology is a major step towards 3D beamforming and imaging using multiple subsea cables. We also show measured cable movements from the mid-Atlantic ridge, whose origin to date is not fully understood.

Finally, this sensing prototype does not disrupt telecom traffic and uses commercial off-the-shelf components, thereby providing a scalble path to realize distributed fiber optic sensing over the entire subsea network.

Session: Advancing Seismology with Distributed Fiber Optic Sensing - II

Type: Oral

Room: K’enakatnu 6

Date: 5/3/2024

Presentation Time: 11:30 AM (local time)

Presenting Author: Mikael Mazur

Student Presenter: No

Additional Authors