Seamless integration of distributed acoustic sensing and passive optical networks for human intrusion monitoring

Passive optical networks (PONs) serve as the backbone of modern all-optical communication infrastructures, while fiber-optic distributed acoustic sensing (DAS) is being applied to various fields as a revolutionary technology. Here we present a study on seamless integration of PONs and DAS for human intrusion monitoring by designing an intensity time-varying frequency shift keying with subcarrier composite spectrum modulation (ITVFS-SCSM) scheme, allowing us to overcome the limitations imposed by the high transmission loss of optical splitters and the low extinction ratio of electro-optic modulators in PONs to the performances of DAS. The ITVFS-SCSM scheme designed can simultaneously realize communication and sensing functions with excellent component and modulation compatibilities within a single channel. Assisted by a time difference of arrival algorithm, the localization of human intrusion with sub-meter accuracy with a high DAS sensitivity of 36.5 pε Hz^-1/2 over 25.45 km fiber are achieved. This work represents a breakthrough in transforming PONs into distributed sensing networks that can accurately localize human intrusions with wide coverage, offering great potential to redefine next-generation PONs with both communication and security functions.