Fig. 1. (a) Configuration of the I-OFDR system. ASE, amplified spontaneous emission source; OBPF, optical bandpass filter; EDFA, erbium-doped fiber amplifier; MZM, Mach–Zehnder modulator; OC, optical coupler; VNA, vector network analyzer; PD, photodetector; ODL, optical delay line. (b) Comparison of the estimated time-domain response between the iDFT-based methods and the adaptive filtering method.

Fig. 2. (a) Estimated time-domain response by applying the adaptive filter in different iterations. The blue line is the estimated response by using the iDFT algorithm. (b) Heat map of the estimated time-domain response in different iterations.

Fig. 3. (a) Estimated OTDs of the two measurement paths as a function of the iteration number. (b) ‖P_new−P‖₂ versus the iteration number.

Fig. 4. The estimated time-domain response under the test of ODL1 and ODL2 when the delay of ODL1 changes from 100 ps to 0 ps with a step of 10 ps.

Fig. 5. Evaluation of the system’s accuracy when ODL1 changes from 100 ps to 0 ps. (a) The deviation of ODL1 in measurement. (b) The measured OTD of ODL2.

Fig. 6. Monte Carlo simulation results of two measurement channels with 570.4 ps and 630.7 ps when the frequency range is 8 GHz. (a) The total variance as a function of the signal-interference ratio. (b) The total error as a function of the signal-interference ratio.

Table 1. Muti-Path OTD Measurement Using Adaptive Filtering