Coherent BOTDA Using Phase- and Polarization-Diversity Heterodyne Detection and Embedded Digital Signal Processing

We have proposed and experimentally demonstrated a configuration of coherent BOTDA using optical phase-and polarization-diversity heterodyne detection and embedded digital signal processing (DSP). With the unwanted probe sideband and Rayleigh scattered noise eliminated by stable electrical filtering, the in-phase and quadrature-phase heterodyne sensing signals in both x- and y-polarizations are received by the phase-and polarization-diversity coherent receiver with independent local light, and processed by the subsequent embedded DSP. The embedded DSP algorithms are designed to recover the baseband BOTDA trace for sensing and remove the intermediate frequency noise (both amplitude and phase noise) to avoid trace distortion. A spatial resolution of ~3 m and temperature accuracy of ±0.3 °C have been achieved over 40-km sensing distance. The configuration, compatible with the detection scheme of optical coherent communication systems, is potential for future high-speed coherent BOTDA with real-time DSP designed to satisfy different requirements.