Securing the Speed: Harvest-Immune Photonic Layer Security in DCI and Metro Networks

The concept of 'harvest now, decipher later' presents a major data security concern in light of thriving quantum computing, rendering traditional public-key cryptography ineffective and undermining even state-of-the-art symmetric block ciphers. Physical layer security (PLS) offers advantages such as enhancing the security of the entire OSI model, including its metadata, with minimal latency and providing robust protection against data harvesting. Multi-THz, high repetition rate mode-locked laser sources have enabled the development of PLS techniques that leverage coherent optical spreading and despreading, phase mask encoding, and under-the-noise transmission. Since capturing multi-THz E-fields is impractical, real-time all-optical decoding is necessary, as offline post-processing yields permanently poor performance (indicated by a negative SNR) for unauthorized detection. This paper reports the demonstrations of PLS transmission of 30 G and 60G Bauds, using QPSK and 16-QAM modulation schemes, achieved over distances of up to 100 km, with a real-time DSP ASIC. These achievements pave the way for high-bandwidth point-to-point harvest-immune optical connectivity.