Hitachi (Tokyo) and Hitachi Cable have used micromachining techniques to develop an optical switch that manipulates optical waveguides with an electromagnet. Many types of optical switches have been developed or have been proposed for communications, depending on the intended function. A micromechanical optical switch could be used as a rerouting switch when obstacles are encountered in a communications path or as a switch to ease the insertion of testing and signal-processing devices.
In the newly developed Hitachi switch, two waveguides are created on a cantilevered quartz layer that has a soft magnetic material affixed to one side. When electricity is applied to an electromagnetic coil, the material on the cantilever becomes magnetic and moves between positions, aligning it with two of four output waveguides. The waveguides couple as dictated by the position of the cantilever. The coupling space is filled with a liquid with the same refractive index as the waveguides to lessen coupling loss. In this manner, two adjacent 1 x 2 switches can be operated in tandem. A permanent magnet embedded in the electromagnet keeps the parts coupled without the current on.
—Courtesy O plus E magazine, Tokyo