In some examples, a micro-electro-mechanical system (MEMS) optical accelerometer includes a housing comprising an internal chamber that includes a Fabry-Perot cavity and a proof mass affixed to the housing via one or more elastic elements, a light source configured to emit radiation, a first detector configured to receive radiation transmitted through the Fabry-Perot cavity and configured to generate one or more signals that indicate a position of the proof mass. The MEMS optical accelerometer further comprises an atomic wavelength reference and a second detector configured to detect radiation transmitted through the atomic wavelength reference and configured to generate one or more signals that indicate a wavelength of the radiation emitted by the light source, and a servomechanism electrically coupled to the second photo detector and the light source, configured to adjust the light source to maintain the radiation emitted by the light source at approximately a selected wavelength.