Fig. 1. Experimental setup for typical single fiber grating interferometric sensing^[7]

Fig. 2. Compensated FBG based sensing system^[11]

Fig. 3. Three common types of FBG-FPI. (a) Pre-placed; (b) mid-placed; (c) post-placed

Fig. 4. FBG-FPI based sensing system using broadband light source^[21-23]. (a) MZI based demodulation; (b) MI based demodulation

Fig. 5. Time division multiplexing system for matched interferometric FBG-FPI sensor^[25]

Fig. 6. Interferometric FBG based hydrophone sensing system proposed by OptoPlan^[34]

Fig. 7. Two types of FBG array based sensing system. (a) Balanced MI sensing system^[37]; (b) imbalanced MI sensing system^[39]

Fig. 8. FBG-FPI hydrophone array^[40]. (a) Partial hydrophone array with 20 mm diameter; (b) picture of 32-element FBG towed hydrophone array

Fig. 9. Heterodyne signal demodulation calculation process

Fig. 10. Several FBG hydrophone probe structures. (a) Piston type^[7]; (b) side pressure type^[20]; (c) end surface stretch sensitization type^[20]

Fig. 11. FBG-FPI hydrophone probe for differential detection^[46]. (a) Schematic diagram; (b) physical map

Fig. 12. Diagram of FBG based accelerometer reported by NRL^[9]. (a) Elastomeric structure; (b) elastic beam structure

Fig. 13. FBG based accelerometer designed by Mita et al^[49]. (a) Diagram; (b) physical map

Fig. 14. Vector sensing base station produced by OptoPlan^[32]. (a) Fiber optic sensor configuration within a sensing base station; (b) physical sensing base station package

Fig. 15. FBG-FPI based thin-shell cylinder structure 1-D accelerator^[55]. (a) Diagram; (b) physical map

Fig. 16. FBG-FPI based vector hydrophone^[56-57]. (a) Photo of accelerator; (b) diagram

Fig. 17. Fiber optic underwater sensor array^[62]. (a) Schematic diagram of sensing system; (b) measurement platform

Fig. 18. Principle of crosstalk in FBG-FPI based sensing system^[66]

Fig. 19. Diversity reception of polarization in FBG-FPI based hydrophone

Fig. 20. Polarization switch-PGC hybrid modulation and demodulation technique^[82]. (a) Schematic diagram of experimental system; (b) pulse timing signal polarization modulation

Fig. 21. Demodulation results of four polarization states^[74]. (a) Fading factor; (b) demodulation phase

Fig. 22. Optical configuration within a fiber optic vector sensor station

Fig. 23. Schematic diagram of active coherence modulation and frequency shift modulation technology principles^[35]

Fig. 24. Demodulated noise spectra^[35]