Fig. 1. Principle of Gaussian beam focusing by a dielectric plano-convex lens^[75]

Fig. 2. Schematic diagram of combining the horn antenna with dielectric lens to get high gain in the wireless link^[75]

Fig. 3. Attenuation coefficient of poly tetra fluoroethylene^[75]

Fig. 4. Measurement result^[75]. (a) Measured radiation patterns at 140 GHz for a dielectric plano-convex lens with a diameter of 10 cm; (b) directivity versus Frequency by experimental measurement

Fig. 5. Photographs of medium used for plano-convex lenses^[75]

Fig. 6. Experimental setup of the integrated optical wireless transmission system based on antenna polarization diversity and PDM^[33]

Fig. 7. Experimental results^[33]. (a) Offline digital signal processing at the receiver; (b) optical spectrum (0.02 nm resolution) after polarization diversity splitting; (c) electrical spectrum after analog down conversion; received Y-polarization constellations (d) before clock recovery, (e) after clock recovery, (f) after CMA equalization, (g) after frequency offset estimation, and (h) after carrier phase estimation

Fig. 8. Experimental results^[33]. (a) Relationship between BER and OSNR of 128 Gbit/s signal after 2 m wireless with and without fiber transmission; (b) relationship between BER and baud rate after 80 km SMF-28 and 2 m wireless transmission

Fig. 9. Experimental results^[35]. (a) Experimental setup of the 6-channel terahertz signal wireless transmission system; optical spectra of (b) multiple-channel signal after PM, (c) LO, and (d) coupled PDM signal; photos of (e) wireless transmitter and (f) wireless receiver

Fig. 10. Experimental results^[35]. (a) Electrical spectrum of the sampled IF signal of Ch6; recovered QPSK constellations of (b) X-polarization and (c) Y-polarization; (d) relationship between BER and input power into each AIPM after 142 cm wireless transmission for the six channels

Fig. 11. Experimental results^[13]. (a) Experimental setup of the wireless transmission in the 80-channel WDM system; optical spectra of 80-channel 20 Gbaud 16QAM signals (b) before and (c) after 20 km fiber transmission; optical spectra of 20 Gbaud 16QAM signal (d) before and (e) after WSS

Fig. 12. Relationships between BER and the input power into PD for 20 Gbaud 16QAM and QPSK signals with and without fiber transmission before wireless transmission at the wavelengths of (a) 1553.33 nm, (b) 1563.05 nm, and (c) 1531.51 nm; (d) BER for 20 Gbaud 16QAM terahertz signal after 20 km fiber and 54 m wireless transmission in all 80 channels^[13]

Fig. 13. THz low noise amplifier^[75]. (a) Gain and noise factor curves; (b) photograph of the high gain terahertz lens antenna; (c) comparison of direct detection scheme and heterodyne detection scheme at the receiver

Fig. 14. Principle of the probabilistic shaping^［42］

Fig. 15. Experimental setup of the photon-assisted 104 m, 200 m, and 400 m THz-wave wireless transmission and NGMI performance of signals^[19-20]

Fig. 16. Experimental setup of the 100/200 GbE real-time photon-assisted THz-wireless transmission system^[55]

Fig. 17. Experimental results^［55］. (a) Optical spectra of the optical baseband signal after OUT; (b) optical signal with tunable optical LO after optical coupler; (c) spectra before and after filtering; (d) setup of THz 2×2 MIMO 3 m wireless link

Fig. 18. BER versus ECL-2 to optical signal frequency spacing^［54］

Fig. 19. BER versus input power into each AIPM based on DP-MZM over two spans of 20 km SSMF and 3 m wireless distance transmission^［54］

Fig. 20. Measured optical spectra for 2×100 GbE^[57]. (a) Baseband optical signals of dual-channels after OUT; (b) optical signals and optical LO after optical coupler; (c) optical signals without and with filtering

Fig. 21. BER versus input power into each AIPM for single channel case and dual-channel case^[55]

Fig. 22. BER versus ROP of each CFP2-DCO module for single channel case and dual-channel case at 385 GHz and 435 GHz^[55]

Fig. 23. Experimental setup of the photonics-based THz data communication and radar sensing integrated system^[81]. (a) Optical spectrum after the PM-OC3; (b) spectra of the de-chirped signal for 40 cm away from the reference position

Fig. 24. BER versus input power for the 16QAM signal after 1 m wireless transmission^[81]

Fig. 25. Principle the photonics-based THz high-resolution radar sensing and high-speed data communication integrated system^［82］. (a) Optical spectrum (0.01 nm resolution) after PM-OC2; (b) NGMI versus optical power into UTC-PD for the PS-256QAM-OFDM signal; (c) spectrum of the de-chirped signal for the 10 cm from the reference position; (d) zoom-in views of the spectra around the peak

Fig. 26. Experimental results^［14］.(a) Experimental setup and photos under different transmission cases, (i) wireless transmission and (ii) metallic hollow core fiber transmission; optical spectra of the coupled (b) QPSK and (c) 16QAM signals after PM-OC; (d) digital signal processing structure at the receiver end

Fig. 27. Relationship between BER and ROP under different transmission cases for QPSK signal with baud rate of (a) 20 Gbaud, (b) 25 Gbaud, and (c) 30 Gbaud (inset: demodulation constellations for (i) metallic hollow core fiber transmission and (ii) wireless transmission when ROP is 9 dBm)^［14］

Fig. 28. Relationship between BER and ROP under different transmission cases for 16QAM signal with baud rate of (a) 10 Gbaud, (b) 12 Gbaud, and (c) 16 Gbaud (inset: demodulation constellations for (i) metallic hollow core fiber transmission and (ii) wireless transmission when ROP is 12 dBm)^［14］