Micro electro mechanical system (MEMS) technology has shown its bright future in many fields, especially in optical communication fields. Because of its inherent advantages such as batch fabrication technique and small size, MEMS is becoming the dominant technology in optical crossconnect switches.  This thesis demonstrated the in-plane electro-thermally actuated uni-directional and novel bi-directional micro-switch prototypes. The novel bi-directional switches, which take the advantage of the features of CMOS technology, with the ability to bend in two opposite directions and to integrate with control circuits, have been fabricated by commercial CMOS technology. These uni-directional micro-switches have been realized by both MUMPS ® technology and CMOS technology to characterize the devices performances. Analytical models based on the specific technologies and finite element model (FEM) analysis were carried out to predict performances of switches with geometry design variations and compared with experimental results. Some interesting polysilicon material properties related phenomena, such as back bending and polysilicon resistance variation during heating and cooling cycles, have been found during experiments. This fundamental study about polysilicon material properties at high temperature in this work provides a reference and guidance for design and operation of these thermally actuated polysilicon devices.