Linearity compensations for a digital variable optical attenuator

A novel digital micro-machined variable optical attenuator (VOA) capable of 40dB dynamic range is described. The device consists of an electromagnetically actuated shutter interposed in a fiber collimator gap and allows adjustment of optical attenuation stepwise in response to inputting TTL pulses. A linear response with respect to driving pulses was achieved by incorporation of a compensation mechanism in the design. Measured performance of the VOA is reported and the characteristics of the device were analyzed with a numerical simulation based on scalar wave theory. The VOA is scalable to a discrete array for the implementation of channel equalization in WDM systems for the realization of high capacity cross-connects.