A Silicon MEMS Optical Switch Attenuator and Its use in Lightwave Subsystems

A single-mode fiber connectorized MEMS (Micro ElectroMechanical System) reflective optical switch attenuator operating in the 1550nm wavelength region is described. The device consists of an electrostatistically actuated gold-coated silicon vane interposed in a fiber gap yielding 0.81 dB minimum insertion loss in the transmit state and high transmission isolation in the reflection state with 2.15 dB minimum return loss. The switch attenuators also work as continuously variable optical attenuators capable of greater than 50dB dynamic range and can be accurately regulated with a simple feedback control circuit. Switching voltages were in the range of 5 to 40 V and a switching time of 64 mu sec was achieved. The MEMS switch can be used in optical subsystems within a WDM optical network such as optical power regulators, crossconnects and add/drop multiplexers. We used a discrete array of 16 switch attenuators to implement a reconfigurable 16-channel 100 GHz spacing WDM drop module of an add/drop multiplexer. Thru-channel extinction was greater than 40 dB and average insertion loss was 21 dB. Both drop-and-transmit of multiple channels (11-18 dB contrast, 14-19 dB insertion loss) and drop-and-detect of single channels (>20dB adjacent channel rejection, 10-14 dB insertion loss) were demonstrated.