Cidra Corporation

USA as Represented by Secretary of the Navy

David G Bellemore

Michael A Davis

David R Fournier

Martin A Putnam

Alan D Kersey

Robert N Brucato

Walter A Helm

D Ralph Jones

William M Stielau

A method and apparatus is provided for detecting peaks in an optical signal. The method comprises the three basic steps of: (1) sampling the optical signal to obtain sampled data containing information about the optical signal; (2) applying a cross-correlation filter on the sampled data to obtain cross-correlated data containing information about one or more peaks in the optical signal; and (3) detecting the one or more peaks in the optical signal based on the cross-correlation data. In one embodiment, the cross-correlation filter has an average value that is less than zero. The step of applying the cross-correlation filter includes reducing random noise present in the sampled data to remove quasi-dc components from the sampled data.

Method and apparatus for detecting peaks in an optical signal using a cross-correlation filter

A method and corresponding apparatus for determining the centroid (V ) of a waveform signal being sampled at a set of parameter values (V , i&equals;1, . . . , n) yielding a corresponding set of sampled amplitudes (A , i&equals;1, . . . , n), each parameter value and corresponding amplitude forming a sampled point (V , A ), the method including the steps of: selecting an amplitude at which to create an interpolated point; interpolating a first parameter value corresponding to the amplitude selected in the step of selecting an amplitude; and performing a centroid calculation using only the sampled points with an amplitude greater than a predetermined threshold. The waveform is sometimes sampled in the presence of background noise, and the method sometimes also includes: estimating the background (B ) for each value in the set of parameter values at which sampling is performed; and reducing the amplitude (A ) of each sampled amplitude by the background (B ) so estimated.

Method for reducing skew in a real-time centroid calculation

A tunable optical device has a compression tuned optical structure and a displacement sensor. The compression tuned optical structure responds to an optical signal, and further responds to a displacement sensor signal, for providing a compression tuned optical structure signal containing information about a change in an optical characteristic of the compression tuned optical structure, and for also further providing an excitation caused by a change in a displacement of the compression tuned optical structure. The displacement sensor responds to the excitation, for providing a displacement sensor signal containing information about the change in the displacement of the compression tuned optical structure. The compression tuned optical structure may be in the form of a dogbone structure that is an all-glass compression unit having wider end portions separated by a narrower intermediate portion. The displacement sensor includes a capacitance sensor affixed to the compression tuned optical structure for measuring a change in capacitance between two parallel and opposing plates that depends on a change in a gap or an area with respect to the two parallel and opposing plates.

Tunable optical structure featuring feedback control

Prior to performing a centroid calculation on a waveform signal that is discretely sampled at a limited number of sample points, the last sample point (V , A ) is eliminated if the magnitude of the amplitude at the first sample point (A ) is greater than the last sample point (A ), and the difference in magnitude between the first and last sample points (A &minus;A ) is greater than the difference in magnitude between the second to last sample point and the first sample point (A &minus;A ). The first sample point (V , A ) is eliminated prior to the centroid calculation if the magnitude of the amplitude at the last sample point (A ) is greater than the first sample point (A ), and the difference in magnitude between the last and first sample points (A &minus;A ) is greater than the difference in magnitude between the second sample point and the last sample point (A &minus;A ). In a second embodiment of the invention, a first centroid calculation is performed using a set of samples in which one side of the waveform signal has the lowest amplitude value sample. Sample values on the side of the waveform initially having the lowest amplitude value are then eliminated until the opposing side of the waveform has the lowest amplitude value sample. A second centroid calculation is then performed and the two centroid calculations are averaged together to arrive at an average centroid calculation. In a third embodiment of the invention, the amplitude components of the waveform sample values are normalized to the lowest amplitude value sample point and a first centroid calculation is performed on the normalized waveform signal. Next, the waveform is normalized to the lowest amplitude value sample point on the other side of the waveform signal and a second centroid calculation is performed. The two centroid calculations are then averaged to provide an averaged normalized centroid calculation.

Method for improving the accuracy in the determination of a waveform center of a waveform signal

A method and apparatus for compensating for systematic error in a wavelength measuring device that provides values for the wavelengths reflected from one or more optical fibers in which fiber Bragg gratings (FBGs) serve as sensors. A high-precision temperature sensing and measuring circuit is used to measure the temperature of a reference FBG that also provides light at some wavelength to the wavelength measuring device. The wavelength reflected by the reference FBG changes with temperature in a way that is known. The (value of) the wavelength being reflected from the reference FBG is then provided to a dynamic compensator, which also receives the wavelengths of light reflected from the sensor FBGs, and the dynamic compensator adjusts the wavelengths of the sensor FBGs using a correction based on the correction required to adjust the value of the wavelength of the reference FBG as measured by the wavelength measuring device.

Method and apparatus for correcting systematic error in a wavelength measuring device

A fiber Bragg grating peak detection system has a broadband source that provides a broadband optical signal, a fiber Bragg grating and a variable threshold and/or grating profile peak detection unit. The fiber Bragg grating responds to the broadband optical signal, and further responds to a physical parameter, for providing a fiber Bragg grating optical signal containing information about the physical parameter. The variable threshold or grating profile peak detection unit responds to the fiber Bragg grating optical signal, for providing a variable threshold or grating profile peak detection unit signal containing information about a peak detected in the fiber Bragg grating optical signal that is used to determine the physical parameter. The variable threshold or grating profile peak detection unit detects the peak using either a variable threshold peak detection or a grating profile peak detection, or a combination thereof. During the variable threshold peak detection, the variable threshold or grating profile peak detection unit determines a respective local threshold value for each wavelength over a spectral band of the fiber Bragg grating optical signal. During the grating profile peak detection, the detection unit determines a grating profile on each side of the peak.

Fiber bragg grating peak detection system and method

A system and method for providing accurate measurements of the reflected wavelengths from multiple strings of fiber Bragg grating (FBG) elements using a single scanning optical filter and an isolated duplicate reference string of FBG elements. A reference string of FBG elements permits precise long-term wavelength determination of sensors by providing real-time adaptive calibration adjustments to correct for any nonlinearities in the response of the single scanning optical filter.

Growing community of inventors

Fairfield, CT, United States of America

David G Bellemore