Method and apparatus for measuring pressure with embedded non-intrusive fiber optics

A method and apparatus is provided for measuring pressure in a pressure containing vessel with a non-intrusive, metal-embedded fiber optic pressure sensor. The pressure containing vessel may, for example, be the combustion chamber of an internal combustion engine. A Fabry-Perot Interferometer is arranged in a terminated, single mode fiber to function as a strain gauge. The fiber Fabry-Perot Interferometer (FFPI) is embedded in a metal part which may be disposed in a wall of the pressure containing vessel. The metal part and FFPI experience a longitudinal strain in response to the pressure in the vessel. In another aspect of the invention, a non-intrusive fiber containing the FFPI may be embedded along the axis of a metal bolt. The bolt may be used to attach a part or structure, which is directly exposed to the pressure, to the wall of the vessel. Consequently, the bolt and FFPI experience a longitudinal strain in response to the pressure on the part or structure. In this aspect, the part or structure exposed to the pressure may be, for example, a fuel injection valve that is attached by the bolt to a cylinder head of an internal combustion engine.U