Fig. 1. Diagram of ultrasound-assisted co-cable identification (ODF: optical distribution frame).

Fig. 2. DSP in ultrasound-assisted co-cable identification: (a) coherent DSP and (b) proposed FUA-UPE method.

Fig. 3. Signal spectrum with residual frequency offset: (a) with V–V FOE and (b) with V–V FOE and proposed F-RFOC. (Δf: frequency offset center; F: sampling rate; FORL: FO reloading; FORC: FO re-compensation.).

Fig. 4. Phase ambiguity between DSP blocks: (a) without and (b) with proposed UIB.

Fig. 5. Result of simulation: (a) frequency offset, (b) estimation error of frequency offset, (c) extracted phase, and (d) PSD of extracted phase.

Fig. 6. Experimental setup for verifying proposed FUA-UPE method (AWG: arbitrary waveform generator; OMFT: optical multi-format transmitter; EDFA: erbium-doped fiber amplifier; VOA: variable optical attenuator; SSMF: standard single-mode fiber; PZT: piezoelectric transducer; OSA: optical spectrum analyzer; OMA: optical modulation analyzer).

Fig. 7. Result of experiment: (a) frequency offset and (b) PSD of extracted phase.