Four-wave mixing in a triple-core microstructure fiber.

We experimentally demonstrate four-wave mixing (FWM) in a triple-core microstructure fiber for a pump wavelength of 1064 nm. We study the transition between the case where FWM happens primarily in a single core and the case where FWM is distributed among multiple cores. The effective nonlinear coefficient is reduced by a factor of 3 (the number of cores) for distributed-core FWM compared with that for single-core FWM. This effect also leads to a three-fold reduction in the FWM bandwidth for distributed-core FWM. We report on the wavelength and polarization dependence of the core-to-core coupling length, and how those phenomena produce power-dependent coupling among the cores. These are the first reported experimental measurements of FWM in a 3-core microstructure fiber providing critical information for their use as nonlinear optical devices.