All-optical switches based on nonlinear fiber gratings

The all-optical switch (AOS) is a key device for future all-optical communication and all-optical computing.There are many types of AOSs that have been investigated;one of them is the fiber-grating AOS,which is easily matched with fiber systems.We first describe two kinds of ordinary silica single fiber-grating AOSs based on the fiber Bragg grating (FBG) and the long-period fiber grating (LPFG),respectively.Both of these require kilowatt switching powers,so they cannot be used in practice.Secondly, we introduce two kinds of highly nonlinear fiber-grating AOSs,one based on a single nonlinear FBG and the other a pair of linear LPFGs connected by a nonlinear fiber.The nonlinear fibers that we use are rare-earth doped silica fibers.Both of the nonlinear fiber-grating AOSs have low milliwatt-level switching powers,and thus may be used in applications.