Two important applications of the fiber Fabry-Perot Interferometer (FFPI) sensor are investigated: (1) an optical binary switch for aerospace application, and (2) an FFPI weigh-in-motion sensor for measuring the weight of trucks traveling down a highway. In the fiber optical switch, the FFPI sensor is bonded to a copper cantilever to sense the elongation of cavity length induced by force applied to the end of the cantilever via a pushed button. Light from a superluminescent diode light source passes through a scanned Michelson interferometer and is reflected from a sensing FFPI and a reference FFPI to produce a fringe pattern. A secondary interferometer uses a distributed feedback laser light source to compensate for irregularities in the mechanical scanning rate of the moving stage to achieve precision measurement of the optical path difference. The system is calibrated by applying known weights to the cantilever. The elongation measured by the FFPI sensor shows excellent linearity as a function of the force applied, and little hysteresis was observed. By comparing the measured force to a threshold, the system produces a binary signal that indicates the state of the pilotactuated system; i. e., whether or not the button has been pushed. In FFPI weigh-in-motion sensors system, the FFPI sensors are installed in metal bars so that they will experience the strain induced by applied loads and are connected to the Signal Conditioning Unit (SCU). The SCU determines the induced phase shift in the FFPI and produces voltage outputs proportional to the phase shifts. Laboratory Material Testing System tests show that the fiber optic sensor response is a fairly linear function of the axial displacement. In highway tests the FFPI sensors showed strong responses and consistently reproduced the expected characteristics of truck wheel crossings. A falling weight deflectometer was used to calibrate the sensor response and predict unknown loads. All sensors in steel bars and aluminum bars showed excellent repeatability and accurate predictions, with an average relative percentage error within 2%. The study on sensor response variation with applied load positions shows a bell shaped distribution. Truck tests on the road sensors indicate that the repeatability of wheel crossings at similar position is good. The sensor can accurately measure axle spacing, speed, and truck class.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 74-75). Also available via the Internet.

Thesis (M.Sc.) -- Memorial University of Newfoundland. / Typescript. Bibliography: leaves 63-64. Also available online.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 88-91). Also available via the Internet.

No description available.

No description available.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 76-79). Also available via the Internet.

No description available.

No description available.

Fiber Fabry-Perot Interferometers (FFPI) are optical sensors which can be used to measure changes in stress or temperature, but efforts continue to improve them. Calculations show that the response can be dramatically altered with a gain inducing medium in the cavity. In order to induce gain, a highly doped Erbium (Er) fiber is incorporated in the FFPI. A pump wavelength of 1480 nm is used with a wavelength near 1550 nm. The pump must be at a significantly higher power level than the signal for gain. In order to correctly interpret responses, it is necessary to characterize the response of the measurement equipment. This includes everything from the laser and photodetector to system losses and the titanium oxide coated fibers. Fabrication of FFPIs involves fusing titanium oxide coated fibers to standard single mode fibers. Directly fusing an Er - doped fiber to a titanium oxide coated fibers was not possible because of incompatible splice conditions required in each case. Instead, an intermediate standard single mode fiber was spliced between them. This lengthened the cavity. Experimental results from the Er - doped Fiber Fabry-Perot Interferometer verified the hypothesis that improvements are obtainable. Overall, the measurements showed a 1.3 dB improvement in the maximum-to-minimum Insertion Loss Ratio.