High-Speed Long-Range BOTDR by Simplex Coding and Short-Time Fourier Transform Processing

Abstract

Conventional frequency-scanned Brillouin optical time-domain reflectometry (BOTDR) reconstructs the Brillouin gain spectrum via step-by-step narrowband filtering, which prolongs the measurement duration. In contrast, digital signal processing (DSP)-based BOTDR significantly accelerates the measurement process by employing broad-spectrum frequency analysis. However, to the best of our knowledge, the sensing range of reported DSP-based BOTDR systems remains limited, primarily due to signal-to-noise ratio degradation resulting from noise accumulation inherent to broadband detection. In this work, we propose a coded coherent-detection BOTDR system followed by short-time Fourier transform signal processing, enabling high-speed long-range sensing. In experimental demonstration, an 80.3 km BOTDR with 127-bit simplex-coded sequences is realized, achieving a frequency resolution of 1.34 MHz and a spatial resolution of 4.57 m, within a 60-s total measurement time.