More than 1.2 million kilometers of fiber-optic cables criss-cross the planet, carrying global phone calls, internet signals and data, but it seems that this network may have another benefit for Earth and ocean sciences.

Low cost global network

By connecting the fiber-optic network with existing remote sensing systems such as satellites, a global low-cost real-time observing network can be created, "and this could be a game-changing global observatory for ocean and Earth sciences," said Martin Landru, professor at Department of Electronic Systems at the Norwegian University of Science and Technology (NTNU) and Head of the Center for Geophysical Forecasting.

Andrew is the lead author of a paper on how this system works published in Nature Scientific Reports, about using fiber-optic networks to monitor whales, storms, earthquakes and ships with new tools that can be used to extract information from these networks, specifically the tool called "interrogator".

Researchers were able to discover more than 800 vocalizations of blue whales and fin whales (Shutterstock)

New eavesdropping tools

The interrogator can be connected to a fiber-optic cable network to send a pulse of light through the cable. Any time a sound wave or an actual wave hits the underwater cable, the fibers bend slightly, and the relative span of the fibers can be measured very precisely.

"This technology has been around for a long time, but it has made a huge step forward in the last five years, so we are now able to use this to monitor and measure acoustic signals over distances of up to 100 km," Landru explains in the press release posted on the university's website. And 200 kilometers. That's the new thing."

Landru's team, in collaboration with researchers from the Norwegian Agency for Joint Services in Education and Research (Sikt) and Alcatel Submarine Networks Norway AS, which supplied the Interrogator's instruments, used a 120-kilometre fiber-optic cable between Longyearbyen (the largest settlement in Svalbard) and Ny-Alesund (a research site on the southwest coast of the archipelago's largest island), monitored the cable for 44 days in 2020, and recorded more than 800 whale sounds.

The researchers were baffled by a series of waves, and because of the new technology, they realized that they were waves sent by distant storms (Shutterstock)

Whale Watching System

The press release also states that the Distributed Acoustic Sensing (DAS) Whale Experiment demonstrates a completely new use for this type of fiber-optic infrastructure, resulting in excellent and unique science.

“The fiber cable between Longyearbyen and Ni-Alesund, which was produced in 2015 after 5 years of pre-planning and work, was intended to serve the research community and the geodetic station,” says Olaf Schilderup, head of the national R&D network at SEKET, in a previous article about the monitoring project. in Ny-Alesund.

Despite the quality of the technology, it is still limited by the range of coverage available to it, which the researchers hope will develop in the future to go beyond the relay stations. Technology is evolving very quickly and we expect to be able to overcome these limitations soon."

The researchers were also able to spot ships passing over or near the cable (Shutterstock)

Ship tracking

In the statement, the researchers also mention that in the process of detecting the whale calls, the researchers were also able to detect ships passing over or near the cable, a series of earthquakes, and a strange pattern of waves that they eventually realized were caused by distant storms. Landru said the measurements were accurate enough. Its measurements can be linked to every event that occurred, including a major earthquake in Alaska.

"We saw a lot of ship traffic of course, and also a lot of earthquakes, the biggest of which was from Alaska. It was big, we saw it on every channel (in the cable) for every 120 kilometres. We also saw that we could detect distant storms," ​​Landru adds.

One example of how the system was able to detect participating ships was the Norbjorn, a general cargo ship that was detected crossing a fiber-optic cable about 86.5 kilometers from Longyearbyen. The researchers were able to estimate the ship's speed from its path through the cable, and then they were able to verify using the AIS trajectory.

The new technology can also help detect earthquakes and their locations (Shutterstock)

Monitor storms and earthquakes

The researchers were puzzled by the series of waves they detected during the observation period, and each event lasted between 50 and 100 hours, as the frequency of the waves increased monotonously during the event, but they eventually realized that the mysterious signals were waves sent by distant storms, and using calculations Landru's team located Tropical Storm Eduardo in the Gulf of Mexico, which was 4,100 kilometers from Svalbard, and a large storm off Brazil, 13,000 kilometers from Svalbard Cable.

Geologists already have a network of sensors that help them monitor and measure earthquakes, which are sensitive tools and provide a great deal of detailed information, but they are expensive devices, and they are not widely distributed like the fiber-optic cable network in the world, and the only drawback of the fiber-optic network It has a lower signal-to-noise ratio, which means that there may be a lot of background noise, and seismic signals will not be as clear or strong against that noise.

But the advantage of the fiber network is that it is already widespread, which means it can provide additional information to existing seismometers. The idea is not to replace the existing system but to supplement it.

There are attempts to use fiber optic networks to monitor subsea pipelines (Shutterstock)

Underwater gas pipeline monitoring

There are also attempts to use existing fiber-optic networks to monitor subsea pipelines, especially after the explosion in late September that damaged Nord Stream 1 and 2 pipelines.

Researchers are wondering about using this fiber-optic technology to monitor and protect infrastructure on the sea floor, but the challenge with pipelines is that they create noise, as gas flows through the pipe.

“With the background noise, we have to characterize the natural variance,” says Landru. “Then if you have something approaching that pipeline, what are the safe limits for that approach? When do you act and what can you detect? We don't know. So the plan is to do ad hoc tests on this.” matter.”

Ultimately, the idea might be to monitor in real time the pipelines to make sure they are safe, especially since the researchers have a real stream of audio data from the Svalbard fiber network.