USA As Represented by Secretary of the Navy

Other

Geoffrey A Cranch

Clay K Kirkendall

Gordon M H Flockhart

Gustavo Kunde Rohde

Jonathan M Nichols

Jacob Grun

Meredith N Hutchinson

Nicole Menkart

Methods, apparatuses, and systems for calculating time delays by a Wasserstein approach are provided. A plurality of signals are recorded by a plurality of sensors (three or more), respectively, and received at a controller. The plurality of signals recorded by the plurality of sensors are generated in response to a signal emitted by a source. The plurality of signals are converted into a plurality of probability density functions. A cumulative distribution transform for each of the plurality of probability density functions is calculated. A time delay for each unique pair of the plurality of sensors is calculated by minimizing a Wasserstein distance between two cumulative distribution transforms corresponding to the unique pair of the plurality of sensors.

Methods, apparatuses and systems for time delay estimation

A method of monitoring a structure for stresses or cracks. A single mode optical fiber is adhered to a structure. The single mode optical fiber includes a first optical cavity. The first optical cavity includes two fiber Bragg gratings with a distance therebetween. The first optical cavity includes a resonance. A frequency shift of the resonance of the first optical cavity is measured with a frequency discriminator. An acoustic emission from the structure is detected based on the frequency shift.

Fiber optic acoustic emission sensor and apparatus

A fiber optic pressure and mass velocity sensor for measuring a shock wave pressure in a solid media includes an optical fiber having a means for measuring a change in an optical path length (OPL) of the fiber when positioned in the solid media caused by the shock wave altering the physical length of the fiber and the refractive index of the fiber. The means for measuring the change in the OPL is coupled at one end to a laser and at its second end to a means for detecting the change in OPL. The sensor has a high operating bandwidth (&#x3e;&#x3e;10 MHz), is sufficiently rigid to withstand the force of the shock wave, has a sensitivity that can also be tailored for the application, and is immune to electromagnetic interference. Measurement can be made on materials under extreme strain conditions, and the sensor can also provide characterization of protective materials such as bullet/blast proof materials.

Fiber optic sensor and method for detecting shock wave pressure and mass velocity in solid media

An apparatus includes a rigid support and a first cantilever including a first optical fiber and a first rigid ribbon. The first optical fiber and the first ribbon, together include a first neutral surface. The first optical fiber is connected to the rigid support. The first optical fiber includes at least one first wave-guiding core running parallel to the first neutral surface. Each of the at least one first wave-guiding core includes at least one first reflector. The first rigid ribbon is affixed to the first optical fiber and to said first rigid support. The apparatus further includes a first membrane surrounding the first cantilever.

Fiber optic cantilever acoustic vector sensor

A planar or cylindrical, cantilever-type apparatus including a rigid support. The apparatus further includes a first optical fiber connected to the rigid support, the first optical fiber including a first neutral axis and at least one first wave-guiding core running parallel to the first neutral axis and located at a distance from the first neutral axis, each of the at least one first wave-guiding core including at least one first reflector. The apparatus further includes a first membrane surrounding the first optical fiber; and a first liquid inside the first membrane and surrounding the first optical fiber, the first liquid including a Reynolds number less than one.

An apparatus and method for characterizing the complex coupling coefficient of a multilayered periodic structure either during or after inscription is described. This apparatus is capable of continuously measuring the complex reflectivity at single or multiple wavelengths to a resolution limited by Rayleigh scattering in the waveguide section where the structure is inscribed. The apparatus is also capable of rejecting undesired signals associated with stray reflections in the system and unwanted environmentally induced change in optical path lengths during the inscription procedure. The complex coupling coefficient of the multilayered periodic structure can be derived from the measured complex reflectivity and can reveal errors present in the structure. The complex coupling coefficient can also be used to derive an error signal to enable implementation of a closed loop inscription system capable of inscribing error free multilayer structures.

Method and apparatus for characterizing a multilayered structure

An apparatus includes a multicore fiber including three cores. The three cores include two pairs of cores, each pair of cores lying in a plane. The planes of the two pairs of cores are non-coplanar. The multicore fiber includes a rosette, the rosette including three coplanar interferometers. Each interferometer of the three interferometers are located in a respective core of the three cores. Each interferometer includes a first reflector and a second reflector. The first reflectors of the rosette are coplanar. The second reflectors of the rosette are coplanar.

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Fairfax Station, VA, United States of America

Geoffrey A Cranch