A fiber optic switch based on the magneto-optic effect of magnetic materials is presented. Due to the optical fiber based construction of the switching device it is suitable for optical fiber networks The on-off function of the switch is useful for isolation and connection of node(s) from a fiber optical network without having to turn off a laser. The switch is based on the Faraday Effect exhibited by magneto-optic materials. The all-fiber magneto-optic switch has a beam splitter at the input that splits an incoming signal into orthogonal polarized paths. Each path has at least one magneto-optic Faraday rotator (MOFR) controlled by a field. When the field is present, the polarization of the optical beam changes, thereby turning the switch on or off depending on the initial polarization of the beam. A beam coupler couples the orthogonal polarized paths at the output of the all-fiber magneto-optic switch. The MOFR is a bismuth substituted iron garnet. In an alternate embodiment the switch is constructed in the Mach-Zehnder configuration, utilizing two 3 dB couplers, isolators and MOFRs. In an alternate embodiment the switch is fabricated on silicon-on-insulator.