Fig. 1. Schematic diagram of the PS-FBG sensing system.

Fig. 2. Index modulation profile of PS-FBG.

Fig. 3. Output spectra of the PS-FBG sensing system.

Fig. 4. FWHM bandwidth versus (a) phase shift and (b) index modulation amplitude.

Fig. 5. (a) Wavelength shift with a strain modulation from 0 to 1  με. (b) Maximum wavelength shift versus phase shift.

Fig. 6. Simulated phase noise with an OPD of 10 mm and Δλ of (a) 0.015 nm and (b) 0.1 nm.

Fig. 7. Simulated results of phase noise at 1 kHz versus OPD when Δλ equals 0.015 nm.

Fig. 8. Measured spectra of the (a) transmission of the PS-FBGs and (b) output.

Fig. 9. (a) The experimental setup for OPD measurements and (b) measured results.

Fig. 10. (a) Measured interference in the time (upper) and frequency (lower) domains and (b) demodulated phase noise level.

Fig. 11. (a) Phase noise level with different OPDs, and (b) phase noise at 1 kHz.

Fig. 12. Measured phase noise level with an interrogation interferometer OPD of (a) 6.8 mm and (b) 10.9 mm.