High-Accuracy Sweep-Free BOTDA Enabled by Simultaneous Full-Field Brillouin Spectra Measurement

We propose and demonstrate a novel dynamic Brillouin optical time-domain analysis (BOTDA) by utilizing frequency-agility double-sideband digital optical frequency comb (DOFC) probes. For the first time, simultaneous interrogation of the complex Brillouin gain, loss, and corresponding phase spectra is realized without frequency sweeping process. An acoustic-optical modulator (AOM) is employed to aid in the simultaneous acquisition of full-field Brillouin spectra without sideband selective optical filters, yielding a fixed frequency offset over the spectral range via direct detection. Through the joint analysis of additional spectra, the measurement accuracy can be significantly improved compared to the traditional single-sideband-based schemes. In addition, frequency-agility DOFC probes are used to improve the spatial resolution while maintaining an acceptable frequency resolution. Eventually, the proposed BOTDA achieves a 4-m spatial resolution and less than 1.53-MHz frequency uncertainty over 10-km fiber with 400-MHz dynamic measurement range for the full-field Brillouin spectra. For proof of concept, dynamic vibration measurement is demonstrated with 40-Hz sampling rate. The proposed scheme with full-field Brillouin spectra measurement provides high-accuracy enhancement, showcasing a promising application for distributed dynamic sensing.