We experimentally demonstrate the photonics-aided wireless transmission of 4×4 multiple-input multiple-output (MIMO) probabilistic shaping 64-ary quadrature-amplitude-modulation (PS 64QAM) millimeter-wave signals at D-band (110-170GHz) over 3.1-m distance with a total bit rate of 1.056Tb/s and a bit-error ratio (BER) under 4×10-2. The employment of advanced digital-signal-processing (DSP) techniques, including probabilistic shaping, Nyquist shaping, and look-up-table (LUT) predistortion, significantly improves the transmission capacity and distance as well as the system performance. To the best of our knowledge, this is the first time to realize $\gt1-Tb/s$ millimeter-wave signal wireless delivery.

We propose and experimentally demonstrate a photonics-aided 2×2 multiple-input multiple-output (MIMO) wireless Terahertz-wave (THz-wave) signal transmission system, which realizes 6×20-Gb/s six-channel polarization division multiplexing quadrature-phase-shift-keying (PDM-QPSK) THz-wave signal delivery over 10-km wireline single-mode fiber-28 (SMF-28) link and 142-cm wireless 2×2 MIMO link with a bit-error ratio (BER) under the hard-decision forward-error-correction (HD-FEC) threshold of $3.8\times10^{-3}$ . Our employed multi-carrier frequencies are located within the range from 375GHz to 500GHz. To the best of our knowledge, this is the first experimental demonstration of 2×2 MIMO wireless transmission of multi-channel THz-wave signal.

Terahertz band (0.1 to 10 THz) with high carrier frequency and large available bandwidth has become a promising candidate to meet the 100 Gbit/s or even 1 Tbit/s data rate required by the future six-generation (6G) mobile communication networks. Compared with the all-electrical methods to generate terahertz signals, the photon-assisted technology can break the bottleneck of the bandwidth limit of the electronics devices, and generate the terahertz signal with high frequency, large bandwidth, flexible tunability and easy integration with the large capacity fiber link. In this paper, we introduce the typical methods to generate terahertz signals based on the photon-assisted technology, and review the representative achievements in different areas of terahertz communication, such as the large capacity terahertz transmission, the long distance terahertz transmission, the real-time terahertz communication, and the integrated terahertz sensing and communication. Based on the photon-assisted technology and various key techniques, devices and advanced digital signal processing (DSP) algorithms, we have obtained many great achievements in broadband terahertz communication and sensing, and the experimental setups and results have also been demonstrated in detail.

A low-complexity and cost-efficient coherent detection-based 100 Gb/s or beyond passive optical network (PON) has attracted a lot of attention in recent years, as this technology offers high receiver sensitivity, colorless frequency selectivity, and linear detection enabling channel impairment compensation in the digital domain. We experimentally demonstrate the first single-wavelength 200 Gb/s coherent PON over 20 km downstream transmission with polarization division multiplexed four-level pulsed amplitude modulation (PDM-PAM-4) signals in the C-band. The intensity modulator replaces the costly in-phase/quadrature modulator, and hardware-efficient carrier recovery technologies are used for recovery of PAM-4 symbols. By using optimized Nyquist pulse shaping, the transceiver bandwidth can be reduced to within 50 GHz. A maximum power budget of 32.5 dB can be achieved for 200 Gb/s/λ PDM-PAM-4 at a bit error rate of 1 × 10 − 2 over 20 km fiber transmission. The possibility of a 200 Gb/s/λ PON is investigated using intensity modulation and coherent detection for the first time to our knowledge.

From the perspective of wireless transmission distance in the terahertz-band (THz-band), the 10-100 m, 100-1000 m, and ≥1000 m ranges are recommended for indoor communications, medium-distance communications, and long-distance communications, respectively. However, most existing photonic terahertz communication demonstrations reported in previous studies have a distance of less than 100 m, with some being even shorter at 10 m or 1 m. In this study, by combining high-gain and high-sensitivity terahertz modules, as well as signal processing technology, we have successfully demonstrated transmission over 850 m with a net rate of 50 Gbit/s at a 320 GHz carrier frequency through outdoor field experimental verification. This particular demonstration represents the most significant distance-rate product, as well as the longest wireless distance achieved so far for photonic terahertz wireless communication. The results demonstrate that the integration of terahertz photonics, electronics, and cutting-edge DSP algorithms, has the potential to enable long-distance and high-speed wireless communication for frequencies ≥300 GHz. Our work represents another significant stride towards achieving our goal of realizing the world's first photonic terahertz-wave communication over kilometer-level distances.

Terahertz (THz) photonics technique can break through the bandwidth limitation of electronic mixing method and be seamless integrated with optical access networks, which has bright prospects in future 6G broadband communication. However, due to the bottleneck of photoelectric conversion efficiency of uni-travelling photodiode (UTC-PD), the power of the generated THz-wave signal is usually only in the microwatt level, and the THz-wave wireless transmission distance is short. In this paper, we summarize the key techniques we use to extend the wireless range for photonics-aided THz-wave communication, which includes THz-wave amplifiers and antennas, heterodyne detection, probabilistic shaping (PS) technique as well as advanced digital signal processing (DSP). Meanwhile, we report our recent research including 104\200\400-m photonics-aided THz-wave wireless transmission records.