United States of America As Represented by the Administrator of Nasa

Hon Man Chan

Allen R Parker, Jr

William Lance Richards

Anthony Piazza

Philip J Hamory

Francisco Pena, Iii

Ryan M Warner

Anthony (Nino) Piazza

A method and system for using a wavelength tunable semiconductor laser as an excitation source of a fiber optics sensing system (FOSS) based on a thermoelectric control of a laser sweep. A device can include an optical fiber; a set of fiber Bragg gratings disposed within the optical fiber; a single-frequency laser (SFL) operatively connected to the optical fiber; a thermoelectric cooler operatively connected to the SFL; a controller comprising a processor in communication with the thermoelectric cooler; and a nontransitory, computer-readable storage medium in communication with the processor. The nontransitory, computer-readable storage medium can store instructions that, when executed by the processor, cause the processor to perform operations including determining a strain value at a first fiber Bragg grating of the set of fiber Bragg gratings based on a second laser signal received at the device that is reflected from an interaction of a first laser signal with the first fiber Bragg grating.

Compact wavelength-swept single longitudinal mode laser for optical frequency domain reflectometry

A method and system for rendering the quaternion shape and orientation of a three-dimensional structure. The proposed system and method keeps track of twist/roll angles and updates its effect on pitch and yaw orientations. The system relies on a single or multi-core optical fiber or multi-fiber bundle containing fiber Bragg grating sensors (FBGs) arrayed in rosettes at 45&#xb0; deltas and spaced at uniform intervals along the entire length of the structure to be monitored. A tunable laser is used to interrogate the sensors using optical frequency domain reflectometry (OFDR), which detects shifts in the wavelength reflected by the sensors in response to strain on the fibers. Each sensor is continuously queried by software which determines the strain magnitude (&#x394;L/L) for each fiber at a given triplet. Given these measured strain values, the software implements a novel quaternion approach to rendering the 3D shape of the fiber including twist.

Fiber optic system for monitoring displacement of a structure using quaternion kinematic shape sensing

The present invention is a temperature sensor for cryogenic systems using a fiber optic interrogation system that is capable of a large number of temperature readings across the cryogenic environment at high resolutions. The invention also includes a method of using such a system to measure temperatures in a cryogenic environment and a method of making such a system.

Fiber optic temperature sensors within inert gas for cryogenic environments

The present invention is an improved fiber optic sensing system (FOSS) having the ability to provide both high spatial resolution and high frequency strain measurements. The inventive hybrid FOSS fiber combines sensors from high acquisition speed and low spatial resolution Wavelength-Division Multiplexing (WDM) systems and from low acquisition speed and high spatial resolution Optical Frequency Domain Reflection (OFDR) systems. Two unique light sources utilizing different wavelengths are coupled with the hybrid FOSS fiber to generate reflected data from both the WDM sensors and OFDR sensors operating on a single fiber optic cable without incurring interference from one another. The two data sets are then de-multiplexed for analysis, optionally with conventionally-available WDM and OFDR system analyzers.

High speed and high spatial density parameter measurement using fiber optic sensing technology

The invention is an apparatus and method of eliminating polarization-induced fading in interferometric fiber-optic sensor system having a wavelength-swept laser optical signal. The interferometric return signal from the sensor arms are combined and provided to a multi-optical path detector assembly and ultimately to a data acquisition and processing unit by way of a switch that is time synchronized with the laser scan sweep cycle.

Apparatus and method for elimination of polarization-induced fading in fiber-optic sensor system

A method and system for rendering the shape of a multi-core optical fiber or multi-fiber bundle in three-dimensional space in real time based on measured fiber strain data. Three optical fiber cores arc arranged in parallel at 120&#xb0; intervals about a central axis. A series of longitudinally co-located strain sensor triplets, typically fiber Bragg gratings, are positioned along the length of each fiber at known intervals. A tunable laser interrogates the sensors to detect strain on the fiber cores. Software determines the strain magnitude (&#x394;L/L) for each fiber at a given triplet, but then applies beam theory to calculate curvature, beading angle and torsion of the fiber bundle, and from there it determines the shape of the fiber in s Cartesian coordinate system by solving a series of ordinary differential equations expanded from the Frenet-Serrat equations. This approach eliminates the need for computationally time-intensive curve-tilting and allows the three-dimensional shape of the optical fiber assembly to be displayed in real-time.

In-situ three-dimensional shape rendering from strain values obtained through optical fiber sensors

A method and system for multiplexing a network of parallel fiber Bragg grating (FBG) sensor-fibers to a single acquisition channel of a closed Michelson interferometer system via a fiber splitter by distinguishing each branch of fiber sensors in the spatial domain. On each branch of the splitter, the fibers have a specific pre-determined length, effectively separating each branch of fiber sensors spatially. In the spatial domain the fiber branches are seen as part of one acquisition channel on the interrogation system. However, the FBG-reference arm beat frequency information for each fiber is retained. Since the beat frequency is generated between the reference arm, the effective fiber length of each successive branch includes the entire length of the preceding branch. The multiple branches are seen as one fiber having three segments where the segments can be resolved. This greatly simplifies optical, electronic and computational complexity, and is especially suited for use in multiplexed or branched OFS networks for SHM of large and/or distributed structures which need a lot of measurement points.

Method and apparatus of multiplexing and acquiring data from multiple optical fibers using a single data channel of an optical frequency-domain reflectometry (OFDR) system

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Canyon Country, CA, United States of America

Hon Man Chan