A programmable and latchable device for wavelength shifting and chromatic dispersion compensating is disclosed. An optical grating such as a Bragg grating, a nonchirped grating, or a linearly or non-linearly chirped grating, is magnetostrictively strained to alter the dispersion compensator characteristics. In a preferred embodiment, a gradient magnetostrictive body is bonded along its length to the fiber grating. In yet another preferred embodiment, a magnetostrictive body is bonded onto the length of the fiber grating, and a gradient generating, programmable and latchable magnet component is placed adjacent the magnetostrictive body. The body is then latchably strained to a desired level by controlling the extent of magnetization in the magnetostrictive material and the magnet so as to induce or enhance chirping characteristics in the grating. Various optical applications using such are disclosed.