Fiber-optic sensor for automotive applications [pressure and temperature measurement]

Our paper presents the first application of a fiber-optic interferometric sensor to real-time monitoring of dynamic pressure and temperature in the exhaust pipe of an automotive engine. The sensor is based on highly birefringent fibers, where the phase shifts between two pairs of polarized modes are induced by two measurands and decoded simultaneously using a coherence-addressing principle. The system allows for unambiguous measurement of pressure and temperature changes in the range of 140 mbar and 100/spl deg/C, and with an accuracy of 2 mbar and 0.4/spl deg/C, respectively, at a sampling rate up to 200 kHz. Preliminary testing of the sensor provided data that allow determination of the flow of exhaust gases and gives information about mass emission. Additionally, the dynamic measurements of pressure make possible diagnosis of the engine operation.