Four-wave mixing with large stokes shifts in heavily Ge-doped silica fibers

Four-wave mixing (FWM) in nonlinear germanosilicate fibers with GeO2 concentrations as high as 67 mol.% in the core is studied theoretically and experimentally. Large frequency shifts of 1875-3829 cm(-1) are observed in the mixed-mode pump parametric process. The dependence of FWM phase matching on the GeO2 concentration, core diameter, and index profile is demonstrated. The 2.5% conversion efficiency of an 887 nm signal to a 1.3 microm communication band is obtained at a 2 W cw pump power inside the fiber.