Abstract: A high pressure sensor which uses a ruby as a pressure sensor is disclosed. This system includes a high pressure Hg lamp which is used to excite the ruby R1 and R2 lines because it has a spectrum which is a good match to the ruby absorption spectrum. The Hg lamp output is filtered to pass wavelengths shorter than about 6300 angstroms so as not to affect the detection system. The light is directed through a dichroic mirror which passes all of the lamp output. The lamp output is then coupled into the optical fiber and carried to the test point. A small ruby is cemented to the end of the fiber and the whole crystal is aluminized. Some of the fluorescence will couple into the fiber and be carried back to the dichroic mirror which reflects ruby fluorescence into the detector but passes any of the original lamp light. The aluminum coating on the ruby increases the amount of fluorescence that is collected.