This Small Business Innovation Research Phase I project aims to develop an oxygen sensor for monitoring explosive mixtures in the head space (ullage) of an aircraft fuel tank. This sensor integrates technological advancements in micro-electronics such as digital signal processors, new vertical cavity surface emitting lasers, high sensitivity absorption spectroscopy, and the development of innovative shields to prevent liquid interferences of optical surfaces. The sensor is expected to detect oxygen concentrations between 5 to 21 percent at a rate of one sample per second, and to perform in conditions where the temperature range is -70 to 120 F and the pressure range is 100 to 760 Torr. The proposed sensor system will be initially compatible for aircraft fuel tanks and later modified for oil tankers and other potential applications.<br/><br/>The successful completion of this program will lead to a rugged and miniaturized oxygen sensor system that is compatible with aircraft fuel tanks. Commercial and military aircraft will greatly benefit from this sensor since it increases their survivability. In addition, the sensor can monitor fuel tanks in oil tankers to prevent oil spillage due to explosions.