In this paper, a MEMS-based monolithic three-axis fiber-optic acceleration sensor is proposed, consisting of three optical fiber collimators and a three-axis acceleration sensing chip. The novel acceleration sensor includes two horizontal sensing units and one vertical sensing unit integrated on a single silicon substrate. Three optical fiber collimators are on the same side of the three-axis sensing chip, thus reducing the package size and cost. In each sensing unit, the micromirror, suspended on a pair of torsion beams, has a torsional angle in response to acceleration in sensing direction. The torsion angle is monitored using fiber-optic detection technique. The sensing system operation principle has been analyzed theoretically, its mechanical performances were simulated using the FEM simulation, and its fabricated process flow was proposed. Using bulk micromachining technologies, the horizontal and the vertical sensing units were successfully fabricated. Finally the individual fabricated sensing units were packaged and tested.
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