Fig. 1. Schematic diagram of channelized spectral splicing technology

Fig. 2. Experimental setup of photonic channel RF receiver based on FWM^[16]

Fig. 3. Schematic diagram of dual optical comb ASOPS. (a) Pump optical comb; (b) Probe optical comb

Fig. 4. Schematic diagrams of spatial magnification technology. (a) Spatial diffraction magnification technology; (b) space-lens magnification technology

Fig. 5. Schematic diagram of time-stretch magnification technology

Fig. 6. Relationship between terahertz pulse shape and round-trips n in the storage ring of ultrafast electron beams with bunch charges of 42, 75, and 118 pC^[35]. (a) 42 pC; (b) 75 pC; (c) 118 pC

Fig. 7. Experimental setup of time-stretch magnification based on distributed Raman amplification ^[36]

Fig. 8. Schematic diagram of time-lens magnification

Fig. 9. Time-lens magnification system using a silicon nanowaveguide^[39]

Fig. 10. Dissipative Kerr soliton dynamics real-time measurement by time-lens magnification system^[40]. (a) Transition from a triplet soliton state to a singlet soliton state; (b) stable triplet solitons at the beginning stage; (c) soliton fusion at the middle stage; (d) stable singlet soliton in the final stage; (e) evolution from doublet solitons to triplet solitons and eventually to a singlet soliton; (f) soliton repulsion at the beginning stage; (g) soliton attraction at the middle stage; (h) stable singlet soliton at the final stage

Fig. 11. Diagrams of pulse measurement experimental setups. (a) FROG technology based on autocorrelation method; (b) SPIDER technology based on dispersive media and Michelson interferometer

Fig. 12. Schematic diagram of 2f system based on time-lens

Fig. 13. Ultrafast optical oscilloscope based on on-chip FWM^[52]. (a) Schematic diagram; (b) experimental setup

Fig. 14. Wavelength-encoded tomography^[58]. (a) Experimental setup; (b) characterization of the imaging depth

Fig. 15. Schematic diagram of ultrafast spectrum analyzer based on time-lens focusing mechanism

Fig. 16. Schematic diagram of PASTA system^[75]

Fig. 17. Experimental setup of full-field measurement based on real-time optical Fourier transformation^[60]

Fig. 18. Schematic illustrating the simultaneous observation of multiplexed high-speed WDM channels [including intensity modulation/direct detection (IM/DD), phase modulation/delay interferometry (PM/DI), and quadrature amplitude modulation/coherent detection (QAM/CD)]^[80]. (a) Optical transmitter enables an over 100 Gbaud symbol rate and multiplexed channels; (b) the multiplexed channels are first demultiplexed, and different modulation formats correspond to different temporal receivers; (c) in the Fourier-domain optical vector oscilloscope, the multiplexed high-speed WDM signal is optically Fourier transformed to a time-mapped spectrum by a dispersive Fourier transform. To obtain the full-field spectrum, a conventional coherent receiver with a chirped LO realizes coherent spectroscopy. Following the digital inverse Fourier transform, synchronized full-field waveforms of each channel can be observed in the time domain

Fig. 19. Experimental setup of real-time Fourier-domain optical vector oscilloscope^[80]

Fig. 20. Simultaneous observation of multiplexed high-speed WDM channels (to simplify the implementation and for ease of reference, four multiplexed channels share a single quadrature amplitude modulator)^[80]. (a) Spectra of a 4×160 Gbit/s QPSK signal acquired by the coherent spectroscopy system and a 0.04 pm resolution OSA; (b) full-field waveforms of single-shot QPSK signals over the whole temporal record length. The four channels are demultiplexed by digital filtering, with CH1 at 1545 nm, CH2 at 1550 nm, CH3 at 1555 nm, and CH4 at 1560 nm; (c) constellation diagrams of four-channel QPSK signals reconstructed from 120 synchronized continuous frames of phase profiles; (d) constellation diagrams from an optical modulation analyser