Optical-actuator frequency-coded pressure sensor.
A small glass tube is deflected by differential thermal expansion effected by low-power 0.82-microm LED light guided in a multimode optical fiber. The resulting deflection is measured, also remotely, by a second LED and a fiber-optic displacement sensor. Amplified feedback from sensor output to thermal-source LED causes continuous oscillation of the tube in the audio range, with a spectral width narrowed by the high mechanical Q. The oscillation period is measured, which is a function of the tube's internal gas pressure, and is largely independent of fiber transmission losses. The device constitutes an all-optical, frequency-coded fiber pressure sensor.
Johnson
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