Point to multi-point physical-layer key generation and distribution in passive optical networks

A point to multi-point physical-layer secure key generation and distribution (SKGD) scheme is proposed and demonstrated in passive optical networks (PONs), where the optical line terminal (OLT) broadcasts optical lights with fast fluctuating states of polarization (SOPs) to the optical network units (ONUs). The highly correlated key waveforms are shared between OLT and ONUs, and the high-level security of the SKGD scheme is guaranteed by the high sensitivity of SOP dynamics associated with the specific fiber links. As a proof of concept, a 3.9 Gb/s SKGD is achieved over 11 km single-mode fiber, where a Sagnac interferometer-based polarization scrambler is constructed as the high-speed random source. Moreover, the generated key sequences are verified to be error free and truly random. The proposed SKGD scheme offers a flexible solution for security enhancement in PONs, and is also compatible with the current PON infrastructure.