Abstract: The fiber-optic magnetostrictive transducer system consists of a sensing element having three dual-strip fiber optic magnetostrictive transducers bonded into a single fiber Mach-Zehnder interferometer operating single mode mounted in a symmetrical orthogonal geometry. The dual-strip fiber optic magnetostrictive transducers have predictable and consistent reproducibility and are comprised of a pair of field annealed metallic glass strips bonded to a coil of optical fiber. This structure is in turn mounted on a bobbin structure where the fiber ribbon is attached to the bobbin only at the two ends of the bobbin. This reduces the possible loading of the transducer due to friction between the optical fiber and the surface of the mounting structure and at the same time provide a long sensing fiber in contact with the magnetostrictive element for high sensitivity.

Abstract: A three-axis fiber optic vector magnetometer is provided for measuring both he direction and magnitude of a DC or low frequency magnetic field. The magnetometer includes an optical interferometer system including a sensing fiber arm disposed with three respective sensing portions perpendicular to one another and attached to a uni-directional sensor material. The interferometer system also includes a reference fiber arm and a laser light source for generating and introducing a laser light into both of the arms. Respective biasing devices generate a reference AC magnetic bias and a respective reference frequency in the three sensing portions. A detecting device detects a reference light signal from the reference fiber arm and the magnetically altered sensing light signal from the sensing fiber arm and forms an interferometer output signal.

Abstract: Three sampling circuits, a subtraction circuit, and a divider circuit cooate to sample an output signal from a nonlinear interferometric sensor at proper times, to subtract output signal samples to obtain a difference signal, and to divide an output signal sample into the difference signal to remove noise-induced modulation from the output signal.

Abstract: A fiber optic magnetometer for detecting DC magnetic fields includes a first optical fiber having a magnetostrictive jacket thereon which defines a sensing arm, and a second fiber defining a reference arm. A first AC magnetic field of frequency .omega..sub.o and a second AC field of frequency .omega..sub.s are imposed on the magnetostrictive jacket so as to cause a time varying optical path length change, having .omega..sub.o, (.omega..sub.o +.omega..sub.s), and (.omega..sub.o -.omega..sub.s) components in the sensing arm fiber. This induces a corresponding time varying phase shift, also having the above components, in light transmitted through the sensing arm fiber which is detected by a phase detector. The phase detector produces a signal proportional to the phase shift, this signal being passed to a lock-in amplifier set to amplify at .omega..sub.o. .omega..sub.s is sufficiently small such that the lock-in amplifier filters all components other than the .omega..sub.o, (.omega..sub.o +.omega..sub.s), and (.

Abstract: A fiber optic magnetometer for detecting DC magnetic fields includes a first optical fiber having a magnetostrictive jacket thereon which defines a sensing arm, and a second fiber defining a reference arm. An AC magnetic field of frequency .omega..sub.o and constant amplitude is imposed on the magnetostrictive jacket so as to cause a time varying optical path length change, having an .omega..sub.o component, in the sensing arm fiber. This induces a corresponding time varying phase shift, also having an .omega..sub.o component, in light transmitted through the sensing arm fiber which is detected by a phase detector. The phase detector produces a signal proportional to the phase shift, this signal being passed to a lock-in amplifier set to amplify at .omega..sub.o. The lock-in amplifier produces an output signal proportional to the amplitude of the .omega..sub.o component, wherein this amplitude is proportional to any DC magnetic fields to which the device is exposed.

Abstract: A fiber optic magnetic gradiometer for measuring both ac and dc magnetic field gradients. The gradiometer utilizes an optical interferometer with magnetostrictive magnetic field sensing elements in each of the interferometer arms. Ac and dc magnetic field biasing is achieved by disposing each of the magnetic field sensing elements within its own magnetic field coil and utilizing a variable dc current source for applying dc current to each magnetic coil. An ac current source at frequency w.sub.o connected across the circuits for the dc current sources is used in conjunction with a variable attenuator to control the ac bias to the respective magnetic coils. The detected output from the interferometer is processed either by bandpass filters or a spectrum analyzer to obtain the signal component at w.sub.o, which is proportional to the external dc gradient magnetic field, and at w.sub.o +w.sub.s, (where w.sub.

Abstract: A fiber optic interferometer-type magnetic field sensor which uses an automatic feedback system to limit the range of the magnetic field experienced by the sensor element. A high frequency bias field is mixed with the external magnetic field to be measured and the resulting interferometer output signal is converted to an electric output signal. The electric output signal is mixed with a reference signal having the same frequency as the bias signal to form a baseband negative feedback signal which is converted to a magnetic field and mixed with the bias and external fields to provide automatic feedback.

Abstract: Improved passive and laser-conditioned magnetic field sensor of compact and integrated construction for enabling the detection of a magnetic field as well as an improved method of manufacture for assembling and selectively pretensioning a subassembly in order to provide an enhanced formation of the subassembly prior to use. The sensor is generally made up of a magnetic field sensing device, first and second fiber-optic elements, first and second couplers, a laser source and a combined detector and analysis means. The first and second couplers interconnect the first and second fiber-optic elements. The magnetic field sensing device is advantageously connected to one of the fiber-optic elements and is generally made up of a magneto-strictive material (MSM) of ribbon-like shape, a nonmagnetic substrate and a sensing element of optic fiber construction. This element is of predetermined and selective multistrand design between its ends and of generally serpentine shape.