System Performance Characteristics of Photonics Enabled THz Wireless Link With White and Flicker FM Noise Laser

Photonics-enabled terahertz (THz) communication systems have rapidly advanced, demonstrating great application potential and providing a new paradigm to meet the growing demand for bandwidth. However, as a critical component in generating THz signals, the laser introduces phase noise (PN) that adversely impacts system performance. This paper investigates the effects of laser white and flicker frequency modulation (FM) noise on THz-wave signal quality. We derive, for the first time, the mathematical relationship between laser FM noise and the minimum bound of bit error rate (BER) performance in the system. Meanwhile, a straightforward and efficient time-domain PN sequences generator based on laser PN power spectral density (PSD) is proposed. We conducted a comprehensive comparison of laser PN behavior under different levels of white noise and flicker FM noise, and evaluated their impact on system performance along with the baud-rate. These analytical results are also valid for traditional coherent optical communication systems. Furthermore, it is successfully demonstrated that the robustness verification of 28 and 36-GBaud dual-polarization (DP) 16QAM photonics-enabled THz transmission under different laser FM noise conditions, and the possibility of optimizing the carrier phase recovery (CPR) algorithm is explored. Results show that under high flicker FM noise conditions, 28 and 36-GBaud DP-16QAM THz-wave signals can achieve post-FEC level performance, even with laser intrinsic linewidths up to nearly 5 MHz and 1 MHz respectively.