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Updated: May 12, 2026

High Speed Sub-GHz Spectrometer for Brillouin Scattering Analysis
Published on: December 22, 2015
Guided acoustic-wave Brillouin scattering noise in few-mode fiber
Abstract:
We describe theoretical and experimental analyses of guided acoustic wave Brillouin scattering (GAWBS) noise in few-mode fiber (FMF). First, we theoretically show the mechanism of GAWBS noise generation through mode-coupling between different linearly polarized (LP) modes in FMF. We show that acoustic modes with wavenumbers along the fiber propagating axis contribute to the mode-coupling in the FMF. Next, we calculate the power spectra of GAWBS noise generated between identical LP modes, different LP modes, and degenerate LP modes in an FMF supporting six LP modes. We then measure the GAWBS noise spectra using a self-delayed heterodyne detection method and confirm good agreement with the calculated results. We find that GAWBS noise generated through mode-coupling between different LP modes exhibits reversibility with respect to the direction of the mode-coupling. Furthermore, we show that GAWBS phase noise generated between different LP modes is converted into intensity noise due to the different group velocities among LP modes in the FMF. We also clarify that the GAWBS noise coefficient is 3 to 4 dB higher than that in standard single-mode fiber (SSMF) since it experiences simultaneous mode-coupling from all LP modes. Finally, we evaluate the impact of GAWBS noise on digital coherent transmission with FMF using the Gaussian noise (GN) model and show that it can cause a substantial transmission distance penalty of as high as 27.7 ∼ 30.0%.
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