“…One of the most widely used techniques is fiber-optic reflectometry based on Fresnel reflection. Two of its major configurations are optical time-domain reflectometry (OTDR) [1,2,3,4,5] and optical frequencydomain reflectometry (OFDR) [6,7,8,9,10]. OTDR, however, generally suffers from its insufficient spatial resolution and relatively long measurement time, whereas OFDR is susceptible to phase fluctuations caused by environmental disturbance.…”