Sub-THz Signal Transmission in Harsh Environments Using L-Band Quantum-Dash Laser Source: Experiments and Modeling

This article demonstrates the generation, and transmission of sub-Tera Hertz (sub-THz signal) using a self-injection locked 1610-nm L-band Quantum-dash laser diode (QD-LD) comb source (QD-sub-THz). First, the obtained 100-GHz sub-THz signal is electrically characterized by the measurement of the signal linewidth and phase noise, which exhibit a value of 1-kHz and −60 dBc/Hz, respectively. Then, the transmission of the sub-THz signal over a hybrid fiber, free-space optics (FSO), and wireless (WL) channel is successfully achieved. We transmitted 16/20 Gb/s quadrature phase-shift keying signals in the 100-GHz sub-THz band through 11.6-km single-mode fiber, 6-m FSO channel, and 3/5-m WL. Bit error rate and error vector magnitude (EVM) less than 3.8 × 10
⁻³
and 37%, respectively, are attained to assess the transmission results. In addition, sub-THz signal transmission through a 3-m in-house emulated foggy channel and smokey channel are examined using different metrics. Moreover, empirical models for signal-to-noise ratio and EVM are deduced as a function of the received electrical power under harsh environments. Finally, a qualitative discussion on the anticipated performance of a higher frequency sub-THz signal (
$\sim$
250 GHz) that may be realized with the L-band QD-sub-THz source, is also presented. This proposed and demonstrated hybrid radio-over-fiber (RoF)/radio-over-FSO (RoFSO) system in the L-band wavelength window strengthens InAs/InP QD-LD as a potential sub-THz source for new radio 5G and 6G communication networks.