Using DFB laser self-injection locked to an optical waveguide ring resonator as a light source of Φ-OTDR

A distributed feedback (DFB) semiconductor laser self-injection locked to an optical waveguide ring resonator (OWRR) is used in a phase-sensitive optical time-domain reflectometry (Φ-OTDR) vibration sensing system as its light source. A frequency-hopping-free period of more than 100 s is realized. A spatial resolution of 13 m at 4700 m and simultaneous measurement of two vibration sources are realized. The measurable vibration frequency is from 8 Hz to the upper limit of the sampling theorem. These satisfactory performances demonstrate that the DFB laser locked to an OWRR is not only cost effective, but also stable and reliable for Φ-OTDR sensing.