Fig. 1. Michelson interference demodulation system based on 3×3 couplers

Fig. 2. Block diagram of NPS demodulation algorithm

Fig. 3. Frequency-response characteristics when fs=125 kHz. (a) Amplitude-frequency; (b) phase-frequency

Fig. 4. Derivative error of ak when ?(t)=cos(4000πt) and r(t)=0.2cos(1.674×105πt)

Fig. 5. (a)Time-domain result and (b) frequency spectrum of εr(t)

Fig. 6. Spectrum of demodulation result

Fig. 7. Block diagram of improved NPS algorithm

Fig. 8. Spectra of demodulation results with NPS algorithm

Fig. 9. (a) Spectrum of RIN and (b) demodulation noise in first experiment

Fig. 10. (a) Spectrum of RIN and (b) demodulation noise in the second experiment

Fig. 11. Spectra of demodulation noise under strong relaxation oscillation

Fig. 12. Demodulation results with FPGA. (a) Time-domain result; (b) spectra