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 inte rconnection based on wavelength division multiplexing (WDM), which can be r ealized as a microelectromechanical system (MEMS) device. The output signal s from a preprocessing integrated circuit (IC) chip (N channels) are conver ted to optical signals of different wavelengths by using wavelength tunable laser diodes and projected onto an array of wavelength-selective photodiod es. Channel connection is made by wavelength matching between the light sou rces and detectors, by using micromechanical Fabry-Perot interferometers. I n this scheme arbitrary 1 to 1 connection as well as 1 to N or N to 1 conne ction is available. Since the input/output connections are made in an optic al manner, the switching state can be reconfigured and the whole switching system can be integrated in a compact space. We have investigated design pr inciple of the micromechanical Fabry-Perot interferometers for tunable phot odiodes to maximize the switching contrast and channel density in a given w avelength range. The preliminary interferometer arrays are implemented by s ilicon-based surface micromachining.