Fig. 1. Block diagram of PS-PAM8 signal generation

Fig. 2. Experimental setup for signal transmission over terahertz hollow-core fiber

Fig. 3. Photo of experimental setup for signal transmission over terahertz hollow-core fiber

Fig. 4. Optical spectra of 5.75 GBaud PS-PAM8 signal in PD and electrical spectra of received signal. (a)(b) Frequency spacing of 97 GHz; (c)(d) frequency spacing of 105 GHz

Fig. 5. BER versus frequency spacing for 5.75 GBaud PS-PAM8 signal

Fig. 6. BER versus baud rate for PS-PAM8 signal at frequency spacing of 105 GHz

Fig. 7. BER versus optical power for 5.75 GBaud PS-PAM8 and PAM4 signals in PD at frequency spacing of 105 GHz (insets I and II are recovered symbols, eye diagrams, and histograms for PS-PAM8 signal at 2-dBm received power and PAM4 signal at 1-dBm received power, respectively)