Fig. 1. Schematic and test results of laser interferometric sensing system^[34]. (a) Comparison of seismic wave signals detected by submarine cable links with seismometer recording during submarine earthquakes; (b) comparison of phase changes detected by terrestrial cables with seismometer recording during earthquakes

Fig. 2. DAS array location and observation results^[37]. (a) DAS array location; (b) raw DAS data; (c) original frequency-wavenumber power spectrum of strain data; (d) Q1 quadrant logarithmic spectrum

Fig. 3. Types of F-ISAC technologies

Fig. 4. Principles of SOP-based sensing technology^[38]. (a) Signal SOP under stable state conditions at receiving end; (b) cable distribution map along deep-sea path; (c) signal SOP distribution induced by seismic or ocean wave; (d) signal SOP distribution after rotation at receiving end

Fig. 5. Schematic diagram of the conventional bidirectional sensing and bidirectional F-ISAC^[40]. (a) Schematic diagram of conventional bidirectional vibration sensing system; (b) schematic diagram of bidirectional F-ISAC system; (c) procedure of digital signal process

Fig. 6. Experimental schematic of the bidirectional F-ISAC system^[40]. (a) Experimental link; (b) PSD of received signals; (c) constellation diagrams of bidirectional transmission signals

Fig. 7. Comparison of sensing performance for transmitted signal phase and SOP^[40]. (a) Test results of optical phase; (b) spectral characteristics of phase signals; (c) test results of SOP; (d) spectral characteristics of SOP signals

Fig. 8. Experimental setup and test results using fiber multiplexing F-ISAC^[42]. (a) Experimental link; (b) microscopic image of the APC chip and schematic diagram of its design principle; (c) relationship between SNR and the frequency of the piezoelectric transducer

Fig. 9. F-ISAC scheme of fiber core multiplexing^[43]. (a) Experimental link; (b) procedure of digital signal process; (c) schematic diagram of vibration loading

Fig. 10. Test results of the F-ISAC system^[43]. (a) Phase difference distribution; (b) average phase difference power distribution; (c) BER performance of each core

Fig. 11. Schematic diagram of F-ISAC system based on FPTs^[45]

Fig. 12. Test results^[45]. (a) Characteristics of Stokes parameters on Poincare sphere under different vibration frequency; (b) time-domain signal of S₁ parameter

Fig. 13. System schemes^[46-47]. (a) BPF method; (b) WF method

Fig. 14. Comparative performance of synesthetic schemes^[46-47]. (a)(b) Test results of BPF method; (c)(d) comparison of sensing performance of the BPF and WF methods

Fig. 15. Schematic and fiber deployment^[48]

Fig. 16. Impact of sensing and communication in TFM F-ISAC system^[48]. (a) SNRs of the 16-QAM signal using different CW power; (b) impact of the 16-QAM communication signal on the sensing performance

Fig. 17. F-ISAC scheme based on two-mode fiber^[49]

Fig. 18. Impact of sensing signal on transmission performance^[49]. (a) Eye diagrams of communication signals with/without sensing signals; (b) impact of sensing signals on communication SNR in OFDM system

Fig. 19. F-ISAC sheme base on 7-core fiber^[50]

Fig. 20. Performance of F-ISAC, and impact each other^[50]. (a) Relative error of Brillouin frequency shift (BFS) and SNR; (b) SNR distribution of BFS under different probe powers; (c) impact of sensing signals on communication signals

Fig. 21. Configuration of F-ISAC system^[51]

Fig. 22. F-ISAC system scheme based on WDM and constellation maps of transmission signal^[52]. (a) Spectra distribution of communication and sensing signals at transmitter; (b) spatial distribution of sensing and communication links; (c) spectral distribution of communication and sensing signals at receiving end

Fig. 23. Monitoring results of traffic parameters and road surface^[52]. (a) Comparative analysis of traffic flow and average vehicle speed; (b) monitoring results of road surface quality

Fig. 24. Schematic diagram of the XPM mitigation principle^[57]. (a) Time-frequency representation of frequency-diverse chirped signals; (b) insertion of power-graded out-of-band chirped signals

Fig. 25. Experimental setup^[57]

Fig. 26. Impact of the optical parameters on the transmission and sensing performance^[57]. (a) Relationship between the maximum sensing power and rise time; (b) relationship between post-FEC BER and sensing power at different frequencies; (c) pre-FEC BER and OSNR distributions under wavelengths

Fig. 27. Setup of real-time QPSK F-ISAC system based on OSC^[60]

Fig. 28. Performance of real-time QPSK F-ISAC system based on OSC^[60]. (a) PSD with different duty ratio on 10.2 km fiber link; (b) SNR obtained at different duty ratios on two fiber links with different lengths

Fig. 29. Schematic of DCI using SHC detection^[62]

Fig. 30. Transmission and sensing performance, and their impact on each other^[62]. (a) BER distributions versus time-domain equalizer length; (b) BER distributions versus east-side communication-to-sensing power ratio; (c) frequency-distance distribution of vibration signals; (d) dual-side communication BER versus received optical power

Fig. 31. Scheme of F-ISAC based on DSCM^[63]

Fig. 32. Transmission and sensing performance, and the impact of CSPR^[63]. (a) BER versus CSPR for 16-QAM signals; (b) BER versus CSPR for QPSK signals; (c) sensing performance versus CSPR; (d) average phase difference versus CSPR

Fig. 33. Principle of time-frequency reused F-ISAC^[64]. (a) Time-frequency characteristics of transmitted light; (b) linear and nonlinear effects in optical fiber including backscattering, chromatic dispersion (CD), SBS, and SPM; (c) principle of CD compensation using SPM; (d) schematic diagram of sensing signal demodulation in frequency domain

Fig. 34. Performance of time-frequency reused F-ISAC system^[64]. (a) BER performance evolution of PAM4 signal as the launching power increases; (b) BER comparison between conventional communication system and F-ISAC system under different received power; (c) sensing accuracy and SNR comparison between conventional sensing system and F-ISAC system; (d) impact of transmission code rate on sensing accuracy

Fig. 35. Working principle and experimental setup of the F-ISAC system using time-frequency reused TS^[65]. (a) LFM generation scheme based on FrFT; (b) design diagram of signal frame format; (c) experimental setup

Fig. 36. Performance of the time-frequency reused TS system^[65]. (a) Estimation error of the timing offset using TS; (b) frequency offset estimation performance and its impact on communication BER; (c) effect of received optical power on communication BER; (d) strain STD with/without communication along the fiber