Continuous chirped-wave phase-sensitive optical time domain reflectometry.

This Letter proposes a novel phase-sensitive optical time domain reflectometry (-OTDR) with continuous chirped-wave (CCW), which can make full use of both time and frequency domain resources. The principle and benefits of CCW -OTDR are elaborated. With the merit of CCW -OTDR, 1.042 MHz sensing bandwidth and 5ε/ strain sensitivity are achieved along a 1013 m fiber with 4.4 m spatial resolution. To the best of the authors' knowledge, this is the first time that a -OTDR achieves megahertz sensing bandwidth with metric spatial resolution, and without limiting the frequency feature of the disturbance. The good performance in long-range sensing is also verified over a 49.7 km fiber. More than that, the digital domain flexibility of the proposed scheme can be used to optimize the measured acoustic signal according to its feature and the practical needs.