The Pressure Sensor design is based on the Fabry-Perot interferometer, in which two minimally separated, partially reflecting surfaces form an optical reflecting cavity. If one of these surfaces is a pressure sensitive diaphragm, changes in external pressure cause a change in depth of the optical reflecting cavity, which in turn alters optical cavity reflectance spectra. For Temperature, the band edge in a special filter glass changes with temperature, and this shift is proportional to temperature change.

The Sensor Instruments (for Pressure and Temperature) contain an 850 nm LED whose emissions reach the sensor via an optical fiber. In the sensor's optical reflecting cavity, the spectral distribution of LED light is modified as a function of cavity depth, and this spectrally altered light is reflected back down the fiber to the instrument. Light returning to the instrument is optically split into two spectral components; the photocurrents from these two components form a ratiometric signal which in turn correlates with changes in the measured parameter. For pressure measurements, differential pressure is obtained by referencing an internal solid state barometric transducer.

The Oxygen Sensor (under development) consists of a luminescent compound in a polymer matrix applied to the sensing end of an optical fiber. The phosphorescence decay time of the compound is dependent on the oxygen concentration at the sensor location. A green light source is briefly turned on to induce phosphorescence in the compound. The green light source is then turned off and the decay time is measured. This decay time is then used to calculate the oxygen concentration at the sensor.