                                        ! " #$%&& !  "  ’"  ’"  ’"  ’("  ’("  ’("  )* + ,  -. ,, -). *,,   Abstract In near future, silicon-on-insulator (SOI) microring resonator are expected to be basic components for wavelength filtering and switching due to their compact size and wide free spectral range (FSR). In this paper, a 2X2 optical switch by using active microring resonator is proposed. The switch is consists of second order serially cascaded microring coupled to a pair of waveguide. The ON/OFF state of the design is control by electric signal which will vary the refractive index. The device is design to operate at 1.55µm wavelength. With a 500nm x 200nm rib dimensions, the design is proven to have single mode behaviour. Finite-Difference Time-Domain (FDTD) method simulation by RSOFT software is use to characterize the device performance. The results show that the 2X2 optical switch proposed can be an efficient device to be functioning in WDM application. Introduction Silicon on insulator (SOI) has a bright future as materials for the integrated photonic system. There are many factors contributed to this such as its high refractive index contrast and low operational cost[1]. In addition, compatibility of the silicon on insulator with the microelectronic fabrication techniques makes it more attractive. Owing this reason, SOI microring resonator has more advantages due to its compactness, fabrication facility and high spectral selectivity [2]. In general, the microring resonator consists of ring waveguide and coupled to a pair of straight bus waveguides. Theoretically, the microring resonator operated by emitting light uniformly from all directions. Light from the cavity can be coupled by evanescently to the waveguide. Meanwhile, the coupling condition is dependent to the microring radius (R), refractive index (n) and the wavelength (λ) of input light. The following equation illustrated the relation between coupling condition and the above three mentioned parameters; m = (2π/λ).R.n (1) where m is an integer, in order to have a resonance at the emission wavelength. In this paper we have designed the 2x2 optical switch based on second order serially cascaded active SOI microring resonator coupled to a pair of straight waveguide [3]. We tuned the refractive index of the microring by using the free carier dispersion effect in order to control the coupling condition [4]. Tuning the refractive index of the microring has been done by applied the bias voltage at the PN junction along the microring resonator [5]. The changes of the refractive index influence the resonance condition for the microring. This will make the resonant wavelength shifted as described below: ∆λ c = λ∆n/n (2) Advanced Materials Research Vols. 378-379 (2012) pp 531-534 Online available since 2011/Oct/27 at www.scientific.net © (2012) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.378-379.531 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 202.185.32.2-02/12/11,03:59:10)