Vector Brillouin Optical Time-Domain Analysis With Heterodyne Detection and IQ Demodulation Algorithm

This paper reports a vector Brillouin optical time-domain analyzer based on heterodyne detection and IQ demodulation algorithm. This approach employs an acousto-optic frequency shifter to generate a single-frequency reference, which simplifies the probe spectrum and directly features the Brillouin gain and phase shift compared with the phase modulation. In addition, the proposed IQ demodulation algorithm makes signal processing easy to implement and allows fast and real-time demodulation. A proof-of-concept experiment is carried out in an ~1.6-km standard single-mode fiber consisting of two different sections of fibers. Both the Brillouin gain and phase-shift spectrograms are successfully measured with an ~2-m spatial resolution. The temperature dependence values of the Brillouin gain and phase-shift spectra are also measured, and the temperature dependence values of the Brillouin frequency shift show excellent linearity larger than 0.999 and almost identical slopes of 1.166 and 1.159 MHz/°C, respectively.