Tunable mode rotator for space-division multiplexing based on a few mode-polarization maintaining fiber.

In this paper, a fiber-based tunable mode rotator is proposed and demonstrated by using the few mode-polarization maintaining fiber (FM-PMF). The mode birefringence in the FM-PMF causes phase difference between two orthogonal degenerate modes. With rotating the FM-PMF segment and getting a variation of aligning angle between the injected LP₁₁ (LP₂₁) mode axis and FM-PMF axis, another intended LP₁₁ (LP₂₁) mode with a certain orientation can be controllably generated at the FM-PMF output.