Noise Equivalent Field Research Articles

Low-Cost Magneto-Optic Sensor Based on Tapered Fiber and Distributed Sensing Concept

In this letter, we present a magnetic field sensor with a noise equivalent field of 500 nT based on a tapered fiber in a magnetic fluid (Fe3O4 nanoparticles dispersed in the deionized water). This sensitivity, which is three orders of magnitude better than the previously demonstrated tapered sensors, is achieved by biasing the fluid material with a ≈1-mT magnetic field. In addition, application of an optical modulator and an auto-balanced synchronized detector increased the sensor output signal-to-noise ratio significantly. Furthermore, a novel method is presented to employ the proposed sensor in a distributed scheme.

Optically sensed EM-field probes for pulsed fields

The characteristics of photonic probes that give them the potential to measure pulsed electromagnetic fields more accurately than has been possible in the past are discussed. An overview of system design is presented with particular emphasis on the transfer functions of appropriate antennas and electrooptic modulators. Noise sources which limit the sensitivity to low signals are discussed and used to determine the noise equivalent field (NEF). The characteristics of some probes developed by the US National Institute of Standards and Technology (NIST) are presented. The NEFs of these probes are about 0.1 V-m/sup -1/-Hz/sup -1/2/ and are about 10/sup 3/ times the theoretical limits. For a 1-Hz bandwidth their dynamic ranges are on the order of 70 dB. Optical guided wave technology holds considerable promise for fabricating modulators with a wide variety of operating parameters that can improve probe performance and extend their applications to a wider region of the electromagnetic spectrum.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>