GaAs-based fiber optic pressure sensor

A description is given of a sensor developed for measurement of hydrostatic pressure up to at least 100 MPa at a standard range of ambient temperatures. The sensor exploits the displacement of the optical absorption edge occurring in semiconductors under the influence of hydrostatic stress as a result of pressure-induced energy shifting of conduction band extrema. The sensing element is composed of an intrinsically pure GaAs single crystal configured in the form of a microprism located at the sensor tip, and attached to two multimode (50/125 μm) optical fibers designed to deliver input light to the sensor and to output a pressure-modulated light signal to the outside of a pressure region. Characterization of the sensor has been performed for pressures up to 100 MPa and for temperatures ranging from 273 to 330 K. A procedure is proposed involving the use of two (active and compensating) sensors to minimize temperature drift through appropriate analog signal processing or, alternatively, through digital computations