Optical-gate based waveguide matrix switches are described. The 4x4 single-mode switches are composed of optical gates and high-silica waveguide splitter, interconnection and combiner circuits. Two types of optical gates, a high-silica waveguide Mach-Zehnder interferometer gate and an InGaAsP laser-diode gate, are tested. The two types of preliminary 4x4 experimental switches exhibited more than 400 Mbit/s switch bandwidth. The optical waveguide gate matrix switch features point-to-multipoint switching and compact structure. The switch may be applied to optical signal processing systems as well as optical communication systems.