Investigation of a Magnetostrictive Fiber Optic Interferometric Sensor
Abstract
This document reports the results associated with a magnetostrictive fiber optic interferometric sensor which was fabricated and evaluated. To evaluate the sensor's performance, a Helmholtz coil was designed and constructed to generate a uniform magnetic field. The sensor's response was determined by examining the amplitude of the interferometer's output light. No DC magnetic fields could be detected due to excessive noise contributed by fused coupler component in the interferometer. AC measurements were successfully accomplished for a 25 Hz magnetic field by inspecting the modulation of the interferometer's output light at 25 Hz. Sensors composed of RF sputtered metal coated fibers did not detect the AC magnetic field because the thin metal films did not generate enough force to change the length of the optical fiber a detectable amount. The sensor did detect the AC magnetic field when the sensor arm was composed of a bulk nickel rod. Thermal annealing the nickel rod in the presence of an external magnetic field improved the sensor's response. Thinning the optical fiber in the sensor arm did not significantly affect the sensor's performance, but increasing the length of the optical fiber did enhance the sensor's response. The sensor's performance also improved when the AC magnetic field was superimposed on a DC bias magnetic field. In the sensor's optimum configuration, and AC magnetic field flux density of 10 mG was detected. Keywords: Magnetic field sensing; Brain activity; Mental activity; Theses; Sensors. (kt)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1989
- Accession Number
- ADA215666
Entities
People
- R. D. Hackett
Organizations
- Air Force Institute of Technology