Interesting nonlinear effects in Er/sup +3-/Yb/sup +3/ co-doped fibers

Interesting nonlinear effects in an Er/sup +3/-Yb/sup +3/ co-doped fiber are described. Second harmonic generation (SHG) in such a fiber with extremely low pump power (<4 mW) and the wavelength tuning of a fiber Bragg grating (FBG) made in such a fiber by means of optical pumping with super high nonlinear refractive index coefficient (>10/sup -13/m/sup 2//W) were experimentally observed. To our best knowledge, both of the two phenomena had not been reported before.