A high-temperature pressure sensor is provided. The sensor includes a quartz substrate with a cavity etched on one side. A reflective coating is deposited on at least a portion of the cavity. The sensor further includes a ferrule section coupled to the quartz substrate with the cavity therebetween. The cavity exists in a vacuum, and cavity gap is formed between the reflective metal coating and a surface of the ferrule. The sensor also includes an optical fiber enclosed by the ferrule section and extending from the cavity gap to an opposing end of the ferrule section and a metal casing surrounding the ferrule section and the quartz substrate with an opening for said optical fiber extending therefrom. The pressure applied to the quartz substrate changes the dimensions of the cavity gap and a reflected signal from the reflective coating is processed as a pressure.