Fiber Optic Cables Listening to Cicada Noise
Scientists at NEC Laboratories operating in a peculiar test bed above Princeton, New Jersey, have stumbled upon a rather remarkable use of a newfangled technique known as distributed acoustic sensing (DAS). The DAS method involves a fiber optic cable strung between three utility poles and then running underground before feeding into an “interrogator,” which fires a laser through the cable and analyzes the light that bounces back.
DAS is increasingly being used by scientists to monitor earthquakes and volcanic activity. Additionally, it has been found that buried systems can detect people walking and driving above. However, the team at NEC Laboratories noticed a strange signal in the DAS data in the spring of 2021. This led them to realize that there was a distinct frequency buzzing everywhere in the data, something that shouldn’t have been there. The team suspected that the signal was not a rumbling volcano, but the loud sounds of the giant swarm of cicadas, known as Brood X, that had just emerged from underground.
The team reached out to Jessica Ware, an entomologist and cicada expert, and she confirmed that the peculiar signal matched the patterns and volume of the cicadas. This discovery indicated that the DAS technology had the potential to eavesdrop on the loud sounds of insects such as cicadas, crickets, and grasshoppers. Ware expressed excitement about the prospect of using this technology to consistently listen in on insect populations.
DAS technology works by transmitting information through fiber optic cables using pulses of light. The interrogator device shines a laser down a cable and then analyzes the light that bounces back to the source. This allows scientists to pinpoint where disturbances occur along the cable. Sarper Ozharar, a physicist at NEC Laboratories, explained that every one meter of fiber can be turned into a kind of microphone.
This discovery opens up a new and powerful way for entomologists to remotely monitor insect populations, which is particularly important at a time when there is insect decline. As researchers continue to explore the possibilities of remote sensing with DAS technology, it is expected that creative applications will emerge. The use of DAS technology to listen to cicadas represents an innovative application of the technology, which was originally developed for monitoring earthquakes and volcanic activity.
