We investigate correlations of the intensity fluctuations of two-dimensional arrays of non-identical, locally-coupled lasers, numerically and experimentally. We find evidence of a power-law dependence of spatial correlations as a function of laser pair distance (or coupling strength) near the phase-locking threshold.
We describe a fiber optic velocity sensor which performs non contact measurements of structural vibrations. The sensor responds directly to the velocity of the sample structure rather than the associated displacement or acceleration through measurement of the Doppler- induced frequency shift of light reflected from the vibrating structure. Light from a single- frequency laser is launched into a fiber optic system which serves the dual role of delivering light to the structure and recollecting the frequency shifted reflected light. The frequency shift, which is proportional to the sample velocity, is processed with a fiber optic Mach-Zehnder interferometer with a relative optical path imbalance. The maximum detectable velocity of the sensor is greater than 1 km/s and is scalable over several orders of magnitude with changes in the fiber optic interferometer. Resolution of the velocity sensor is 80 micrometer/second/(root)Hz.
Nonlinear transduction mechanism in electrostrictive and magnetostrictive materials is exploited to demonstrate multiplexed low frequency fiber optic electric and magnetic field sensors. The sensor utilizes a single interferometer and a single unmodulated laser while demonstrating extremely low cross-talk between the electric and magnetic channels. Low frequency electromagnetic signals from remotely located electric and magnetic dipoles are detected with the fiber optic sensor.
We demonstrate a fiber optic interferometric dc and low frequency voltage sensor based on the electrostrictive effect in lead magnesium niobate (PMN) transducers. The sensor exhibits ultra-low drift and has a noise floor of 35 nV/?Hz at 10 mHz and 20 nV/?Hz at 1 Hz.
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