Coherent Kramers-Kronig Receiver for $\boldsymbol \Phi$-OTDR

The phase-sensitive optical time-domain reflectometry (Φ-OTDR), which could locate and demodulate perturbation along tens of kilometers sensing fiber with high spatial resolution and high sensitivity, has been applied in many fields, such as seismic wave detection, structure health monitoring, and so on. The phase retrieval of the Rayleigh backscattering light is the most critical process of Φ-OTDR; therefore, the research on the phase retrieval of Φ-OTDR has attracted lots of attentions. It should be noted that in fiber-optic communications, the phase retrieval is also a crucial process for phase-encoded schemes. Particularly, as an effective phase retrieval scheme, the Kramers-Kronig (KK) receiver proposed recently has become a hot topic in fiber-optic communications for its high spectral efficiency and low requirement of continuous-wave-to-signal power ratio. Therefore, this paper discusses the feasibility of applying the KK receiver into Φ-OTDR and analyzes the signal retrieval error with KK relation in Φ-OTDR; then, its performance in phase retrieval is verified through numerical simulations and experiments. All the results show that generally the KK receiver is a good phase retrieval scheme for heterodyne Φ-OTDR.