A system is disclosed for measuring internal cylinder pressure of a combustion chamber at least partially formed by a cylinder head. The system may include an emitter configured to generate and emit a wavelength of energy along a surface of the cylinder head, and a target inline with the emitter and configured to receive the wavelength of energy. The system may also include a controller in communication with the emitter and/or target. The controller may be configured to correlate a distortion of the wavelength of energy to the internal pressure.