This paper presents a mathematical model to predict the dynamic behavior of a MEMS based variable optical attenuator (VOA) and compares with ANSYS simulation values. The optical attenuation is achieved by the electrostatic actuation of a metal coated cylindrical waveguide. The waveguides are suitable for micromachined configurations. Electrostatic modeling employed in this analysis also takes into consideration the cylindrical geometry of the waveguide. The modeling utilizes Rayleigh-Ritz energy method in evaluating the fundamental and the higher natural frequencies of the system. The predicted natural frequencies of the optical system have been compared with ANSYS simulations to validate the proposed model. The variation of the dynamic performance of the system with respect to the critical design parameters, such as, applied voltage, electrode gap and length of the actuator is also presented. The results clearly indicate the applicability of the proposed method to optical attenuation.
This paper describes the design of a novel electrostatically actuated optical attenuator that uses the electrostatic actuation of a cylindrical waveguide. The optical MEMS device consists of an electrostatically actuated waveguide positioned in a V-groove and overhanging at the end to act as a cantilever. The optical fiber waveguide can be sputtered with a thin film of gold that acts as a good electrode. The electrostatic force between the electrodes actuates the input fiber under the application of a voltage and causes misalignment between the input and output fibers and thereby attenuates the amount of light transmitted to the output fiber. Electrostatic modeling of the system presented in this paper is simple and sufficiently accurate. The proposed analytical model takes into consideration the geometry of the cylindrical electrodes. The geometrical relationship of the cantilever beam to the range of the biasing voltage is also discussed. The paper presents the variation of deflection of the waveguide and the variation of power loss with respect to the applied voltages. The obtained results clearly demonstrate the efficient use of the proposed method and modeling approach.