Characterizing the Strain and Temperature Dependence of Brillouin Gain Spectra in a PANDA-Type Few-Mode Fiber

초록

A few-mode optical fiber (FMF), which supports higher-order spatial modes, has been extensively researched for optical communications and sensor applications. It serves as a potential platform of mode division multiplexing and fiber sensing with special functionalities. A PANDA-type FMF, featuring strong linear birefringence while also supporting higher-order modes, has proven effective in stabilizing the intensity distribution of these modes by breaking the inherent degeneracy in the LP modes of circular-core FMFs. In this work, we experimentally demonstrate the characterization of various intra- and intermodal Brillouin gain spectra (BGS) in a PANDA-type FMF, with a particular focus on the measurement of strain and temperature dependence. Brillouin optical correlation-domain analysis with differential measurement is employed to analyze the multipeak BGS of higher-order intramodal Brillouin scattering in a distributed manner, and a far-field detection scheme is implemented to distinctly analyze the Brillouin gain in higher-order modes, despite significant mixing with the fundamental mode.

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