Effect of pump-read optical path difference on the measurement of Brillouin dynamic grating spectra localized by the correlation domain technique with a single laser setup

Abstract

In correlation domain distributed measurement of Brillouin dynamic grating (BDG) in polarization maintaining fiber, adjustment of the frequency modulation (FM) phase between the pump and read lightwaves is essential. We experimentally evaluated the phase difference impact on the measurement. A single laser setup can acquire the BDG spectra with higher stability, but the FM phase relation is fixed. Therefore the FM synchronization is not guaranteed for all points of the fiber under test due to the birefringence of the fiber. In this report, we varied the optical path difference between the pump and the read lightwaves, showing the spectrum degradation.