A passive bidirectional audio transmission system with integrated sensing, energy supply, and communication

• Presents a novel, fully passive optical platform integrating three key functionalities. • Enables simultaneous quasi-distributed acoustic sensing and bidirectional audio communication. • Employs UWFBG arrays to fundamentally overcome signal fading in traditional DAS. • Demonstrates high performance over 10 km: >51 dB SNR for both links and 1.21 mW power delivery. This paper proposes a passive bidirectional audio transmission system that enables the simultaneous transmission of energy, sensing, and communication. The system achieves passive bidirectional audio transmission over a 10 km optical fiber link integrated with fiber Bragg gratings. In the uplink, a phase-sensitive optical time-domain reflectometry (Φ-OTDR) technique incorporating integrated ultra-weak fiber Bragg gratings (UWFBGs) is employed to realize quasi-distributed acoustic sensing and audio reconstruction across the entire fiber link, achieving a signal-to-noise ratio (SNR) of 52.22 dB and a frequency response ranging from 500 Hz to 3 kHz. For the downlink, a self-developed InGaAs/InP photovoltaic power converter (PPC) is utilized to simultaneously supply power and transmit audio signals, eliminating the need for any external power source. Under low-light conditions, the system still maintains an audio SNR of 51.8 dB and an energy conversion efficiency of 13.2 %, thereby enabling a fully passive terminal. Experiments show that the system still possesses excellent performance in long-distance, unpowered, and low-light environments, providing an effective communication solution for special scenarios such as high-voltage and mining operations. This study presents a novel terminal-passive optical fiber platform that integrates sensing, power supply, and communication, offering a new solution for safe and reliable optical communication and perception in extreme environments.