Characterization of space dust using acoustic impact detection.

This paper describes studies leading to the development of an acoustic instrument for measuring properties of micrometeoroids and other dust particles in space. The instrument uses a pair of easily penetrated membranes separated by a known distance. Sensors located on these films detect the transient acoustic signals produced by particle impacts.

Compact directional acoustic sensor using a multi-fiber optical probe.

A compact directional acoustic sensor is described which uses a two-fiber optical probe, a light emitting diode (LED), a photo-diode detector, and a slender cylindrical cantilever to the end of which is attached an optical reflector. Acoustically induced transverse displacement of the cantilever tip modulates the light reflected by it into the collection fiber, which conveys the light to a photo-detector. Directional sensitivity is achieved through the dependence of the collected light on the cosine of the angle between a line through the centers of the two fibers and the cantilever tip displacement (the sound direction).

Planar flexible fiber-optic interferometric acoustic sensor.

A planar flexible fiber-optic interferometric acoustic sensor has been developed by wrapping optimized single-mode fibers in a planar spiral form and then embedding the fiber in a thin polyurethane layer. Both the acoustic and the acceleration responses have been found to compare favorably with those of a planar polyvinylidene fluoride sensor of similar geometry.

Microbend fiber-optic sensor.

Intensity modulation induced by microbending in multimode fibers is considered as a transduction mechanism for detecting environmental changes such as pressure, temperature, acceleration, and magnetic and electric fields. A generic microbend sensor has been defined and studied, and its components, such as sensing fiber, light source, optical fiber leads, and detector, have been examined and optimized. Finally, the generic microbend sensor has been tested demonstrating good performance.

Dynamic thermal response of single-mode optical fiber for interferometric sensors.

The dynamic temperature phase sensitivity of a three-layer optical fiber is calculated for unjacketed as well as Al- and Hytrel-coated fibers. The calculations include both the variation of the refractive index with temperature and the thermally induced axial and radial strains. The calculated phase sensitivity indicates that it is currently possible to measure a 1-microdegree C temperature change at frequencies exceeding 50 kHz with 1 cm of a metal coated optical fiber.