With the great demand for WDM (Wavelength Division Multiplexing) optical communications, optical switches are expected to become one of the dominant components in future networks. Conventional mechanical switches suffer from poor reliability and large size; however, many micromachined optical switches with moving mirrors have been proposed for high scale OXC (Optical Crossconnect) or ADM (Add/Drop Multiplex) because of the low power consumption and high reliability of these switches. In this paper, we introduce the technological trends of optical switches using MEMS, related micromachining technologies and their characteristics.