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Polarization and modal analysis of a large-area, polarization-maintaining higher-order-modes fiber via a Bragg grating

We report a method for the characterization of the higher-order modes in polarization-maintaining multimode optical fibers using a Bragg grating. We evaluate a 400 µm diameter, polarization-maintaining higher-order-modes fiber by inscribing a Bragg grating, resonant at the wavelength $\lambda \sim {1067}\;{\rm nm}$λ∼1067nm. By comparing the reflection spectra of the light polarized along the slow and the fast axes of the fiber and using the derived mathematical relations, we estimate the birefringence and the polarization-extinction ratio of the various higher-order modes in the fiber. This represents a simple and attractive approach for a detailed investigation of the multimode polarization-maintaining fibers that are emerging as an invaluable tool for advanced manufacturing, defense, bio-imaging, and telecommunications systems.