Existing fiber optic cables can monitor whales

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A new study demonstrates for the first time that the same undersea fiber optic cables used for internet and cable TV can be repurposed to connect to marine life at unprecedented scales, potentially transforming critical conservation efforts.

“Eavesdropping at the Speed ​​of Light: Distributed Acoustic Sensing of Baleen Whales in the Arctic,” was published July 5 in Frontiers in Marine Science. It describes whale tracking using fiber optics and a technique called distributed acoustic sensing (DAS).

The illustration shows how the DAS works. An interrogator (a) sends a laser pulse from a ground station through the fiber optic cable. The cable has flaws (b) that underwater sounds displace slightly. This returns a signal that the interrogator can interpret as acoustic data at regular intervals or channels (c).

“Sound travels five times faster in the ocean than in air,” said Léa Bouffaut, postdoctoral researcher at the K. Lisa Yang Center for Conservation Bioacoustics at the Cornell Lab of Ornithology and first author of the study. “Because whales are very vocal, acoustic monitoring is a very effective way for us to assess where they are and where they are going.”

Putting this detailed information in the hands of conservationists and policy makers could have a significant impact. Nearly 50% of large whale species are classified as endangered. They face challenges such as warming oceans and increased human maritime activities that negatively affect their environment and their ability to communicate.

Bouffaut completed the study with collaborators while at the Norwegian University of Science and Technology. She and the Yang Center team will now advance DAS research in two main areas: assessing the quality of received audio signals and artificial intelligence software to sift through the massive acoustic output of DAS, which can add up to several terabytes of data per day..

Traditional methods of acoustic whale monitoring involve deploying an array of hydrophones to detect sound waves in a specific area. According to Bouffaut, due to the relatively high costs associated with the operation (instruments, ship and crew time for deployment and recovery), acoustic data remains sparse and the oceans sampled unevenly.

By using fiber optics, scientists could have access to many more sensors over longer distances, allowing them to better monitor whales in real time.

“The technology behind DAS is totally different from monitoring sound waves directly with an underwater microphone,” said Holger Klinck, director of the Yang Center. “What we are recording are changes in the timing of light pulses that are backscattered by small flaws in the fiber optic cable. We can then convert this signal into sound. That’s why we call them “virtual” hydrophones.

The monitoring would use one of the unused spare fibers, also known as “dark fiber”, which is usually included with telecommunications wiring harnesses. These dark fibers can be operated without disrupting existing data streams at the shore end of the cable.

“My hope is to further develop this technology and make it available to everyone involved in marine conservation,” Bouffaut said. “This technology could make the future much brighter for whales.”

Meher Bhatia is a science writing intern and Pat Leonard is a writer at the Cornell Lab of Ornithology.

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