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Numerous ground tests and platform tests were conducted to evaluate platform integration issues and the performance of the POLATOMIC 2000 magnetometer, a laser-pumped helium-4 total magnetic field sensor. These results are compared with those from lamp-pumped helium-4 magnetometers, the AN/ASQ-208 and the AN/ASQ-81 The sensitivity of the digital AN/ASQ-208 magnetometer is 3 pT/square roots of Hz from dc to 216 Hz; and, the analog AN/ASQ-81 has a slightly higher noise floor. The POLATOMIC 2000 noise floor is less than 0.3 pT/square roots of Hz. For airborne measurements, the sensor noise is not usually the limiting noise. In the magnetic anomaly detection (MAD) band (0.04 Hz to 0.4 Hz), for example, substantial reduction of platform and environmental noise is necessary. Important sources of noise are geology, geomagnetic, platform, gradient, and wave. In order to reduce the effect of these noise sources, ancillary sensors are used in conjunction with noise models. These sensors are fluxgate magnetometers, accelerometers, and a low-noise C-code GPS. The performance of the POLATOMIC 2000 is described, as is the platform integration. Results of ground tests and flight tests are summarized, and the noise models and the effectiveness of the ancillary sensors for ambient and platform noise reduction are discusses., Prepared in collaboration with Applied Science Corp, Horsham, PA and Polatomic, Inc. Richardson, TX.

This patent discloses an optical system wherein light is transmitted through fiber-optic members orthogonally configured in a triaxial arrangement for measuring the magnetic field vector preset in the environment. In one preferred embodiment, a set of three fiber-optic coils positioned coaxially along respective orthogonal axes and having predetermined lengths and diameters are coupled to a source of polarized light for transmitting the light subject to Faraday rotation of its plane of polarization. In another preferred embodiment, light, not necessarily polarized, is transmitted along respective orthogonal axes through a set of three bifurcated fiber-optic cables each formed having a reference branch on which a magnetostrictive material is intimately connected to produce optical path length changes related to the magnetic field component along the respective axes. Photodetectors are used in both embodiments to produce current signals indicative of characteristic changes in the transmitted light, and the current signals are digitally processed to provide magnitude and directional information regarding the magnetic field vector., Supersedes PAT-APPL-308 310-81, AD-D010 247.

A fiber optic sensor system and associated technique is disclosed for measuring an electric field wherein a sensor arm of optical fiber cable is wound about a core member of piezoelectric material. A reference arm of optical fiber cable substantially equal in optical path length to the sensor arm is isolated and connected in parallel to the sensor arm so that coherent light generated by a single model laser source may be split through the fiber-optic arms and recombined after passage there-through for phase comparison. When subjected to a local electric field, the core member of piezoelectric material varies in dimensions and thereby causes a change in the stain in the optical fiber cable of the sensor arm. Relative phase changes in the coherent light caused by the resulting optical path length change of the strained homodyne demodulator and deterministive of the value of the local electric field. A vane-type shield is adapted to be rotated about the core member for periodically reducing the local electric field to near zero thereby providing a reference level for field measurement., Supersedes PAT-APPL-442 497-82, AD-D010 483.

A gated fiber optic sensor system is disclosed for increasing the effective optical path of a length of optical fiber cable. A pulse of polarized light having a known optical wavelength is directed into a length of optical fiber cable for propagation therethrough in a cyclic path. A planar semiconductor member is mounted in the path of the polarized light pulse at the Brewster angle to permit continuous transmission of the polarized light pulse through the cable until a light pulse of a second optical wavelength is made to impinge upon the semiconductor member, changing the reflectivity characteristics thereof and causing the polarized pulse to be extracted from its cyclic path for detection and processing. In one preferred embodiment, the optical fiber cable is configured in a loop to provide the cyclic path for the epolarized light pulse, while in another preferred embodiment, the pulse path is provided by a straight section of optical fiber cable forming a part of a highly reflective cavity having reflectors on either end. (Author), Supersedes PAT-APPL-395 557-82, AD-D010 331.

Document describes an interferometrically tuned laser resonator for selectively resonating at a desired wavelength or fluorescent line. A dielectric reflector having reflectance characteristics which shift toward shorter wavelengths at incident angles not normal thereto is rotatable mounted at one end of a laser cavity along its axis. Rotation of the reflector permits adjustment of the incidence angle to obtain maximum cavity gain at a desired fluorescent line over adjacent competing lines. (Author), Supersedes PAT-APPL-210 902-80, AD-D009 452.