THz Integrated Sensing and Communication With Full-Photonic Direct LFM Reception and De-Chirping for D-Band Fiber-Wireless Network

Integration of sensing and communication (ISAC) systems at the terahertz (THz) band will play a crucial role across a myriad of applications in the 6G era, profoundly enhancing our daily experiences. Photonic-based THz ISAC systems harness the inherent broad bandwidth to directly generate high-frequency broadband signals, ensuring seamless integration with fiber-wireless networks and demonstrating significant potential. Current ISAC systems employ linear frequency modulation (LFM) signals for sensing struggle to directly receive and de-chirp THz echo signals, which, nonetheless, curtails sensing capabilities; moreover, no research has yet investigated the impact of varying fiber lengths on the performance of downlink sensing signal transmission and uplink echo signal return. This article presents a THz photonic-based ISAC system designed to surmount these limitations. At the radar receiver, full-photonic direct reception and de-chirping of D-band LFM signals are realized by a high-bandwidth thin-film lithium niobate Mach-Zehnder modulator (TFLN-MZM); moreover, we evaluate the impact of different fiber lengths on system performance. Our system attains an exceptional range resolution of 6 mm and a peak data rate of 116 Gbit/s at a center frequency of 134 GHz, with a calibrated mean ranging error of less than 3 mm.