Hiding an Ear in Plain Sight: On the Practicality and Implications of Acoustic Eavesdropping with Telecom Fiber Optic Cables

—Optical fibers are widely regarded as reliable communication channels due to their resistance to external interference and low signal loss. This paper demonstrates a critical side channel within telecommunication optical fiber that allows for acoustic eavesdropping. By exploiting the sensitivity of optical fibers to acoustic vibrations, attackers can remotely monitor sound-induced deformations in the fiber structure and further recover information from the original sound waves. This issue becomes particularly concerning with the proliferation of Fiber-to-the-Home (FTTH) installations in modern buildings. Attackers with access to one end of an optical fiber can use commercially available Distributed Acoustic Sensing (DAS) systems to tap into the private environment surrounding the other end. However, because the optical fiber alone is not sensitive enough to airborne sound, we introduce a “Sensory Receptor” that improves acoustic capture. Our results demonstrate the ability to recover critical information, such as human activities, indoor localization, and conversation contents, raising important privacy concerns for fiber-optic communication networks.