Photonic Layer Security Transmission of 100 Gbit/sec Over 200 km of Populated Legacy WDM Network

Photonic layer security is demonstrated over 200 km of a loaded dense wavelength-division multiplexing (DWDM) network. The secure channel achieves 100 Gbps throughput with photonic-encrypted coherent transmission and continuously updating photonic keys. The signal is effectively concealed under optical noise, harvest-proof, and lacks offline decryption capabilities, ensuring post-quantum resilience. Additionally, successful coexistence with seven conventional coherent channels, both in-band and out-of-band, is demonstrated in a real-world scenario.