Telecommunications service Researchers use fiber optic cables to measure rockfall in Brienz GR

Research teams have detected shock waves on underground Internet fiber optic cables during the rockfall in Brienz GR in 2023. The triggered ground waves led to extremely small expansions and compressions in the optical fibers.

Researchers from the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and the Swiss Federal Institute of Technology (ETH) Zurich were able to measure the deformations in real time and determine their origin in the fiber with an accuracy of a few meters.

For the measurement, laser pulses were sent through an unused fiber in a telecom cable, as the WSL announced on Tuesday. If the fiber is deformed, the pulses return in a different form. The method can be used wherever fiber optic cables for communication are buried in the ground, which is the case in many places in Switzerland, for example along railroad lines.

The most difficult thing about fiber optic detection is filtering out the signals it is looking for from the countless other vibrations caused by trains, traffic or rivers. Artificial intelligence can automatically recognize the signals with the help of an algorithm. 95 percent of the rock movements could be correctly identified, as the researchers reported in the journal Geophysical Research Letters.

According to the WSL, the fiber optic method could be helpful in monitoring potential rockfalls, avalanches, earthquakes and debris flows with local precision and over large distances.

SDA