In this article, recently developed high-speed, real-time fiber optic sensor demodulation techniques based on low coherence interferometry and phase-shifting interferometry are presented. The demodulation schemes are used in a pressure sensor system that consists of a Fabry-Perot sensing interferometer and an integrated optical circuit (IOC) phase modulator that is used as a reference interferometer. Various conventional phase-stepping algorithms and novel algorithms with error compensations are investigated in order to reduce the errors in the demodulated phase signals. The errors introduced in the phase demodulation arise from many sources, including random intensity measurement errors, phase-shifting errors, and signal-related errors associated with time delays. Numerical analyses are conducted to compare the performances of the demodulation schemes based on different phase-shifting algorithms. These analyses will provide guidelines for choosing appropriate algorithms in sensor demodulation schemes and improving the sensor accuracy and bandwidth.
Forced oscillations of piezoelectric, micro-electromechanical (MEMS) resonators fabricated as clamped-clamped composite structures are studied in this effort. Piezoelectric actuation is used to excite these structures on the input side and piezoelectric sensing is carried out on the output side. Each resonator structure is modeled as an Euler-Bernoulli beam with axially varying properties across the length and distributed actuation. A nonlinear integro-partial differential system is derived to describe the micro-resonator. For weak damping and weak forcing, the method of multiple scales is used to obtain an approximate solution of the system about a post-buckling position. The different modeling assumptions are presented and discussed, and the analytical prediction is compared with experimental observation.
AC space charge self-fields in gyroiron beams are studied via a set of particle equations. The study addresses the linear stability of beams in tapered magnetic fields as well as the nonlinear-multi frequency saturation of space charge instabilities.