Fig. 1. Typical example of downconversion signal processing in ranging with comb IMBs. Mea, measurement signal; Ref, reference signal; PD, photodetector; BM, balanced mixer; LO, local oscillator; DAQ, data acquisition.

Fig. 2. System diagram of the real-time RPD suppression. BS, beam splitter.

Fig. 3. Experimental setup of ranging with the comb IMBs suppressing the RPD in real time. PBS, polarization beam splitter; H, half-wave plate; Q, quarter-wave plate; PS, power splitter; BPF, bandpass filter.

Fig. 4. RF response of the measurement PD. (a) Beat f_IMB with the signal comb detected individually; (b) beat f_IMBL with the local comb detected individually; (c) beat f_IMB and (d) beat f_IMBL with the two combs (of the same optical power) detected simultaneously. P_1 dB, RF power at the 1-dB compression point.

Fig. 5. Experimental results of real-time RPD suppression. (a) Comparison of the distance variation measurement results without and with the real-time suppression; (b) zoom-in details of the suppressed results in the Y-scale; (c) Allan deviation of the measurement results with and without the RPD suppression.