Self-coherent photonic terahertz link at 300-GHz-band against modulated jamming.

Terahertz (THz) intensity modulation technology is crucial for future low-cost 6G networks but is vulnerable to jamming. While frequency hopping (FH) counters single-tone jamming, our evaluation demonstrates its weakness against modulated jamming. Specifically, we demonstrated that while FH with a 40 GHz carrier separation is effective against single-tone jamming, it fails against modulated jamming. To address the vulnerability, we propose a self-coherent THz system where the transmitter generates both the radio frequency and local oscillator signals. This architecture separates the desired signal from the modulated jamming for secure communication. Moreover, using wavelength-tunable lasers for FH, the system resists both modulated and single-tone jamming. We demonstrate secure 1-Gbit/s transmission at 275 GHz against a 235 GHz modulated jamming signal and the reverse case. This cost-effective scheme improves THz link resilience to multiple jamming types and supports secure THz wireless communications.