Design of MEMS optical switches

As a result of more stringent bandwidth requirements, MEMS optical-fiber switches are gaining in significance in optical communication. It is thus necessary to realize a highperformance switch. At the same time, the design of these MEMS devices poses many challenges as a number of properties need to be considered and traded off against one another. This chapter discusses the design issues in relation to two major characteristics of the optical switch: optical performance and electromechanical properties. For optical design, the insertion loss induced by fiber misalignment; Fresnel reflection; and micromirror-related issues, including coating material, thickness, and roughness of the surface, are investigated. The effect of the mirror on different wavelengths will then be presented. Polarization-dependent loss (PDL) is also be discussed in detail. For electromechanical design, the actuation of the optical switch is elaborated. After a brief comparison among different actuating mechanisms, the electrostatic comb-drive actuator is discussed from the viewpoints of force, stiffness, displacement, and stability. Besides, an actuator with large displacement amplification is introduced to produce a latched output.