Cidra Corporation

David R Fournier

Michael A Davis

David G Bellemore

John A Moon

James R Dunphy

Joseph Francis Pinto

Robert N Brucato

Charles Winston

Richard Todd Jones

James S Sirkis

Ralph W Jones

Christopher Chestnut

William M Stielau

An optical spectrum analyzer (OSA)sequentially or selectively samples (or filters) a spectral band(s)of light from a broadband optical input signaland measures predetermined optical parameters of the optical signal (e.g., spectral profile) of the input light. The OSAis a free-space optical device that includes a collimator assembly, a diffraction gratingand a mirror. A launch pigtail emits into free space the input signal through the collimator assemblyand onto the diffraction grating, which separates or spreads spatially the collimated input light, and reflects the dispersed light onto the mirror. A &#x3bb;/4 plateis disposed between the mirrorand the diffraction grating. The mirror reflects the separated light back through the &#x3bb;/4 plateto the diffraction grating, which reflects the light back through the collimating lens. The lensfocuses spectral bands of light (&#x3bb;&#x2013;&#x3bb;) at different focal points in space. One of the spectral bandsis focused onto a receive pigtail, which then propagates to a photodetector. A pivoting mechanismpivots the diffraction gratingor mirrorabout a pivot pointto sequentially or selectively focus each spectral bandto the receive pigtail. A position sensordetects the displacement of the diffraction gratingor mirror.

Optical spectrum analyzer

An optical system has a broadband source and a chirped Bragg grating etalon. In operation, the broadband source provides a broadband optical signal. The chirped Bragg grating etalon responds to the broadband optical signal, for providing a chirped Bragg grating etalon optical signal having a precise set of the optical reference signals. The chirped Bragg grating etalon may include a pair of chirped Bragg gratings. The precise set of the optical reference signals is determined by the spacing of the chirped Bragg gratings of the chirped Bragg grating etalon. The precise set of the optical reference signals includes a series of peaks covering most of a source spectral width of the broad optical source signal with the power at the beginning and end of the spectrum passed unaffected by the chirped Bragg grating etalon due to the limited bandwidth thereof.

Optical system featuring chirped Bragg grating etalon for providing precise reference wavelengths

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 fiber Bragg grating reference module provides a precise temperature reference for a temperature probe, including a thermistor, located in close proximity thereto, and includes an optical fiber having a fiber Bragg grating therein, a glass element and a reference housing. The fiber Bragg grating has two ends and with a coefficient of thermal expansion. The glass element anchors the two ends of the fiber Bragg grating, and has a substantially similar coefficient of thermal expansion as the coefficient of thermal expansion of the fiber Bragg grating to ensure that the glass element does not substantially induce strain on the fiber Bragg grating as the ambient temperature changes. The reference housing has a cavity and also has a means for receiving and affixing one end of the fiber Bragg grating and for suspending the fiber Bragg grating in the cavity leaving the other end of the fiber Bragg grating free to move as the ambient temperature changes without inducing strain in the fiber Bragg grating. The glass element includes a glass tube collapsed over the entire length of the fiber Bragg grating. Alternatively, the glass element includes a glass tube locally collapsed at the two ends of the fiber Bragg grating over a part of length of the fiber Bragg grating.

Fiber bragg grating reference sensor for precise reference temperature measurement

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.

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Ashford, CT, United States of America

David R Fournier