All-optical Brillouin dynamic grating generation in few-mode optical fiber.

We report, for the first time (to our knowledge), generation of Brillouin dynamic gratings (BDGs) in few-mode optical fibers. A moving acoustic grating is generated by stimulated Brillouin scattering using a writing beam in one fiber mode, which is used to reflect a reading beam at a different wavelength in another fiber mode. With single-end pumping, a BDG with a tunable reflectance of up to 0.1% is demonstrated in a 15 km specially designed two-mode optical fiber.