Design and analysis of micromechanical tunable interferometers for WDM free-space optical interconnection

This paper proposes a new concept of high density chip-to-chip optical interconnection based on wavelength division multiplexing (WDM), which can be realized as a microelectromechanical system (MEMS) device. The output signals from a preprocessing integrated circuit (IC) chip (N channels) are converted to optical signals of different wavelengths by using wavelength tunable laser diodes and projected onto an array of wavelength-selective photodiodes. Channel connection is made by wavelength matching between the light sources and detectors, by using micromechanical Fabry-Perot interferometers. In this scheme arbitrary 1 to 1 connection as well as 1 to N or N to 1 connection is available. Since the input/output connections are made in an optical manner, the switching state can be reconfigured and the whole switching system can be integrated in a compact space. We have investigated design principle of the micromechanical Fabry-Perot interferometers for tunable photodiodes to maximize the switching contrast and channel density in a given wavelength range. The preliminary interferometer arrays are implemented by silicon-based surface micromachining.