Strain gauges are widely employed in microelectromechanical systems (MEMS) for sensing of, for example, deformation, acceleration, pressure, or sound . Such gauges are typically based on electronic piezoresistivity. We propose integrated optical sensors which have particular benefits: insensitivity to electromagnetic interference, no danger of igniting gas explosions with electric sparks, small multiplexers (1 mm2) and high-speed readout. We use photonic microring resonators in SOI technology as accurate sensors that can be integrated with MEMS. In this paper, we present a characterization of the relation between an applied strain and the shift in the optical resonance wavelengths of such resonators. This characterization includes the influence of the width of the waveguide and of the orientation of the silicon crystal. © 2013 IEEE.