Time-Expanded Φ-OTDR Based on Binary Sequences

In this letter, the capabilities of time-expanded phase-sensitive optical time-domain reflectometry (TE $\Phi $ -OTDR) using binary sequences are demonstrated. We present a highly flexible and integrable TE $\Phi $ -OTDR approach that allows a customized distributed optical fiber sensor (range, spatial resolution, and acoustic sampling) by simply changing the length of the binary sequence and the reference clock frequencies of the binary sequence generators. The here presented architecture eliminates the need for the cumbersome arbitrary signal generators used to date to create the dual-comb spectra for interrogating the fiber. In this approach, the use of large binary sequences allows us to obtain dual combs in a simple and cost-effective way. Spatial resolution of ~1 cm is achieved, attaining ~15,000 independent measurements points along the interrogated fiber, with a capability of sensing ~30,000 measurements points.