A twin-interferometer fiber-optic readout for diaphragm pressure transducers

A twin-interferometer fiber-optic readout scheme has been developed to monitor the deflection of pressure transducer diaphragms. This technique has a potential advantage at high temperatures, since the circuitry is kept at room temperature and is coupled to the sensor head via optical fibers. The interference scheme used differs from conventional interferometry in that: light is carried forward to the diaphragm and backwards to the photodetectors using a single fiber; and the cleaved fiber end-face itself acts as the reference plane for the interference cavity. A single interferometer cannot uniquely determine the direction of motion, but two such interferometers in parallel, i.e. the twin-interferometer, do provide the necessary information to measure both the magnitude and direction of deflection. Prototype sensor assemblies and detection circuitry have been developed and tested in an industrial setting. Limiting factors on sensor performance have been identified. This technique should also be applicable to other mechanical sensors in which deflections must be monitored.<>