Nano-scale displacement measurement of MEMS devices using fiber optic interferometry

In this paper, the application of fiber interferometry in the nano-scale displacement measurement of microelectromechanical system (MEMS) device is being presented. Fiber optic interferometry combines the benefits of the optical fiber such as lightweight, small size and wide bandwidth with the high resolution, high sensitivity capability of the interferometry. It also provides easier setup and offers lower energy loss than the conventional free-spaced interferometry. The fiber optic interferometric system comprises a laser source and a 2 X 2 fiber coupler. The reference arm and the sensing arm of the interferometer are formed within a sin-le output of the coupler. The resultant interference intensity is measured at one of the fiber coupler input. The fiber optic interferometry could be used for the MEMS with moving structure. A case study is being carried out to investigate the displacement of the micromirror in the MEMS Fabry-Perot Filter. The mirror is being driven by the comb drive actuator under the effect of applied voltage. It selectively reflects certain wavelengths while allows others to pass through determined by the air cavity length. The displacement under different applied voltages will be measured using the fiber optic interferometry. The experiment and the result will be demonstrated.