Image-matching assisted dual-frequency phase-sensitive optical time domain reflectometry

An image-matching assisted dual-frequency phase-sensitive optical time domain reflectometry (Φ-OTDR) is proposed and demonstrated. Compared to the conventional dual-frequency Φ-OTDR, which retrieves data via curve matching, the proposed scheme can effectively improve the temporal resolution and measurement precision while keeping the spatial resolution without additional hardware. In the experiments, with a 10 s temporal window, the proposed scheme realized the same measurement precision as the conventional method that used a 40 s window, suggesting a fourfold improvement of temporal resolution. When both used the 10 s temporal window, the measurement error was suppressed from 21.4% to 1.2% in the sensing for a 2 m hot zone at the end of a 90-m fiber.