Interferometric Sensors For Dc Measurands -A New Class Of Fiber Sensors

Fiber optic interferometric sensors are typically susceptible to environmentally induced thermo/mechanical perturbations at low frequencies, which preclude their use as dc sensors. However, by using a fiber/transducer configuration in which strain in a linear transducing element is converted nonlinearly into strain in the fiber, the measurement frequency can be up-converted from dc to a frequency where near shot noise limited performance can be obtained. This technique is applicable to the dc or low frequency measurement of any field variable for which a suitable non-linear displacement to strain configuration can be constructed. In this paper the operation of a dc displacement, acceleration and pressure sensor is described, as well as the multiplexing of these sensors.