Fiber Optic Sensing Publications and White Papers

Distributed Temperature and Strain Sensing

“Distributed fibre-optic temperature and strain measurement with extremely high spatial resolution” – Photonik 2012 issue
An article reviewing the novel method of scanning the Rayleigh scattering along a length of optical fibre to enable a distributed sensor system where every point along the fibre acts as a sensor.

 

“Structural health monitoring: Angling for the air” – Composites World November 2012 issue
An overview of Luna’s technology applied to structural health monitoring (SHM) for composite aerostructures.

 

“Appeal to the sensors” – Aerospace Testing International November 2012 issue
Using distributed fiber sensing technology as an alternative to traditional foil strain gages, to test composite materials in the aerospace industry.

 

“Effects of defects” — Aerospace Testing International July 2012 issue
Using fiber optic strain-sensing technology to detect defects during manufacture and fatigue cycling of composite structures

 

Harnessing the Power of Fiber Fingerprints
Modern, very high resolution reflectometry can be used to measure the Rayleigh backscatter from the fiber and thus map the imperfections that cause it. Once this map, or fingerprint, is stored it can be used in some very interesting applications from distributed fiber optic sensing to network security and intrusion prevention.

 

“Superior Fatigue Characteristics of Fiber Optic Strain Sensors”

N. A. A. Rahim et. al., “Superior Fatigue Characteristics of Fiber Optic Strain Sensors,” Aircraft Structural Integrity Program Conference (ASIP), San Antonio, Tx, 2012.

In this work, the performance of surface-bonded, low bend loss, polyimide coated optical fiber sensors during high-strain fatigue tests is reported.  The susceptibility of strain gages to fatigue damage when strained cyclically at high amplitudes limits its suitability for high-cycle monitoring.  Superior fatigue characteristics of fiber optic strain sensors paves the way for overcoming this limitation and supports its use for fatigue testing and other high-strain cyclic monitoring.

See the poster here.

 

“One Centimeter Spatial Resolution Temperature Measurements from 25 to 850 0C Using Rayleigh Scatter in Gold Coated Fiber”

A. K. Sang et al., “One Centimeter Resolution Temperature Measurements from 25 to 850° C Using Rayleigh Scatter in Gold Coated Fiber,” Quantum Electronics and Laser Science Conf., Baltimore, MD, 2007.

We present the use of swept wavelength interferometry for distributed fiber-optic, temperature measurements of up to 850 0C over a 1m fiber segment in commercially available, single mode, gold coated fiber.

 

“Distributed Strain and Temperature Sensing in Plastic Optical Fiber using Rayleigh Scatter”

S. T. Kreger et al., “Distributed Strain and Temperature Sensing in Plastic Optical Fiber Using Rayleigh Scatter,”  SPIE Defense, Security, and Sensing, Orlando, FL,  2009, pp. 73160A-73160A.

We now demonstrate that distributed sensing with mm-range spatial resolution in off-the-shelf plastic multi-mode optical fiber is feasible.

 

“Distributed Fiber-Optic Temperature Sensing using Rayleigh Backscatter”

D., K. Gifford et al., “Distributed Fiber-Optic Temperature Sensing using Rayleigh Backscatter,”  31st European Conf. and Exhibition Optical Communications, Glasgow, Scotland, 2005, Vol. 3, pp. 511-512.

We present a novel technique for distributed fiber-optic temperature sensing based on measuring the temperature-dependent spectral shift of the Rayleigh backscatter signal along an optical fiber. Swept-wavelength interferometry is used to measure the Rayleigh backscatter.

 

“Strain Measurements of a Fiber Loop Rosette using High Spatial Resolution Rayleigh Scatter Distributed Sensing”

D. K. Gifford et al., “Strain Measurements of a Fiber Loop Rosette using High Spatial Resolution Rayleigh Scatter Distributed Sensing,”  Fourth European Workshop Optical Fibre Sensors, Porto, Portugal, 2010, pp. 765333-765333.

Strain is measured with high spatial resolution on fiber loops bonded to a metal test sample to form a fiber rosette. Strain measurements are made using an Optical Backscatter Reflectometer to detect changes in the phase of the Rayleigh Scatter of the fiber with 160 μm spatial resolution along the length of the fiber.

 

“One Centimeter Spatial Resolution Temperature Measurements in a Nuclear Reactor Using Rayleigh Scatter in Optical Fiber”

A. K. Sang et al.,”One Centimeter Spatial Resolution Temperature Measurements in a Nuclear Reactor using Rayleigh Scatter in Optical Fiber,” IEEE Sensors J., vol. 8, no. 7, pp. 1375-1380, July 2008.

We present the use of swept wavelength interferometry for distributed fiber-optic, temperature measurements in a Nuclear Reactor over 3m fiber segments of commercially available, single mode fibers.

 

“Distributed Optical Fiber Sensing for Wind Blade Strain Monitoring and Defect Detection”

A. Kaplan et al., “Distributed Optical Fiber Sensing for Wind Blade Strain Monitoring and Defect Detection,” 8th International Workshop Structural Health Monitoring. Stanford, CA, 2011.

We present results from using optical frequency domain reflectometry for high-density distributed fiber optic measurement of strain in a composite wind blade during dynamic fatigue testing.  This work  illustrates the potential of distributed fiber optic strain measurement for early defect detection in large-scale composite structural health monitoring.

 

“High Precision, High Sensitivity Distributed Displacement and Temperature Measurements using OFDR-Based Phase Tracking”

D. K. Gifford et al., “High Precision, High Sensitivity Distributed Displacement and Temperature Measurements using OFDR-based Phase Tracking,” 21st International Conf. Optical Fibre Sensors, Ottawa, Canada, 2011, pp. 77533I-77533I.

Optical Frequency Domain Reflectometry is used to measure distributed displacement and temperature change with very high sensitivity and precision.  The effective length change, or displacement, in the fiber caused by small temperature changes was measured as a function of distance with a precision of 2.4 nm and a spatial resolution of 1.5 mm. The temperature changes calculated from this displacement were measured with precision of 0.001 C with an effective sensor gauge length of 12 cm.

 

“High Resolution Distributed Strain or Temperature Measurements in Single- and Multi-mode Fiber Using Swept-Wavelength Interferometry”

S. T. Kreger et al., “High Resolution Distributed Strain or Temperature Measurements in Single-and Multi-mode Fiber using Swept-wavelength Interferometry,” Optical Fiber Sensors, Cancun, Mexico, 2006.

We describe the use of swept-wavelength interferometry for distributed fiber-optic strain and temperature sensing in single mode and gradient index multimode fiber.  The method is used to measure strain in a four-strand multimode cable under twist.

 

“Distributed Strain and Temperature Discrimination in Unaltered Polarization Maintaining Fiber”

M. E. Froggatt et al., “Distributed Strain and Temperature Discrimination in Unaltered Polarization Maintaining Fiber,” Optical Fiber Sensors, Cancun, Mexico, 2006.

A Rayleigh scatter-based distributed measurement technique is presented in which strain and temperature discrimination is achieved using standard polarization maintaining fiber as the sensor.

 

“Swept-Wavelength Interferometric Interrogation of Fiber Rayleigh Scatter for Distributed Sensing Applications”

D. K. Gifford et al., “Swept-wavelength Interferometric Interrogation of Fiber Rayleigh Scatter for Distributed Sensing Applications,” Optics East, Boston, MA, 2007 pp. 67700F-67700F.

We review recent advancements in making high resolution distributed strain and temperature measurements using swept-wavelength interferometry to observe the spectral characteristics of Rayleigh scatter in optical fibers.

 

“Monitoring Strain during Composite Manufacturing using Embedded Distributed Optical Fiber Sensing”

D. K. Gifford et al., “Monitoring Strain During Composite Manufacturing Using Embedded Distributed Optical Fiber Sensing,” SAMPE Technical Conf. Proc., Long Beach, CA, 2011.

We use high resolution distributed fiber optic sensing to monitor the strain in a composite sample during a VARTM manufacturing process.  This work illustrates that distributed fiber sensing can be used to monitor composite structures during the manufacturing process to determine strain levels, monitor infusion and detect defects.  The embedded sensors can then further be used to measure strain during load tests of the structure or in-service after manufacture, providing an integrated method for non-destructive testing.

 

“Embedded and Surface Mounted Fiber Optic Sensors Detect Manufacturing Defects and Accumulated Damage as A Wind Turbine Blade is Cycled to Failure
J. R. Pedrazzani et al., “Embedded and Surface Mounted Fiber Optics Sensors Detect Manufacturing Defects and Accumulated Damage as a Wind Turbine Blade is Cycled to Failure” SAMPE Tech. Conf. Proc.: Emerging Opportunities: Materials and Process Solutions, Baltimore, MD, 2012.

High resolution fiber optic strain sensing is used to monitor the distributed strain during fatigue testing of a 9-meter CX-100 wind turbine blade with intentionally introduced defects

 

“Defect Detection during Manufacture of Composite Wind Turbine Blade with Embedded Fiber Optic Distributed Strain Sensor”

S. M. Klute et al., “Defect Detection During Manufacture of Composite Wind Turbine Blade with Embedded Fiber Optic Distributed Strain Sensor,” 43rd Proc. International SAMPE Tech. Conf, Ft. Worth, TX, 2011.

High resolution fiber optic strain sensing is used to monitor the distributed strain throughout the manufacturing process of a 9-meter wind turbine blade with intentionally introduced defects.  Distributed strain measurements throughout the depth of the spar cap provide valuable information at intermediate points in the manufacturing process which elucidate defects both prior to and during infusion.

 

“Fiber Optic Distributed Strain Sensing used to investigate the Strain Fields in a Wind Turbine Blade and in a Test Coupon with Open Holes”

J. R. Pedrazzani et al., “Fiber Optic Distributed Strain Sensing used to Investigate the Strain Fields in a Wind Turbine Blade and in a Test Coupon with Open Holes,” SAMPE Tech. Conf. Proc., Charleston, SC, 2012.

High resolution fiber optic strain sensing is used to make measurements of the distributed strain present in both a 9-meter CX-100 wind turbine blade with intentionally introduced defects and in a laminated composite coupon test sample possessing three open holes.  High-resolution distributed strain measurements reveal the complexly structured strain fields existing in these laminated composite materials.

 

“Distributed Fiber Optic Strain Measurement Using Rayleigh Scatter in Composite Structures”

E. Sanborn et al., “Distributed Fiber Optic Strain Measurement using Rayleigh Scatter in Composite Structures”,  SEM Conf., Montville, CT, June 2011, Vol. 6.

This paper presents the use of distributed fiber optic sensing to achieve centimeter level resolution strain data along the entire length of a large composite beam.  A section of optical fiber was embedded into a fiberglass rope, which in turn was embedded into the composite beam during the manufacturing process. The beam was experimentally tested in four-point bending at the North Carolina State University Constructed Facilities Laboratory, and the strain profile along the entire length was measured using the embedded optical fiber.  The experiment confirms the potential of embedded fiber optic distributed sensing to be used for real-time health monitoring, or as a process feedback in an instrumented structural system.

 

“High-Resolution Extended Distance Distributed Fiber-Optic Sensing Using Rayleigh Backscatter”

S. T. Kreger et al., “High-resolution Extended Distance Distributed Fiber-Optc Sensing using Rayleigh Backscatter,” 14th Int. Symp.: Smart Structures and Materials & Nondestructive Evaluation and Health Monitoring, San Diego, CA 2007, pp. 65301R-65301R.

We describe the use of swept-wavelength interferometry for distributed fiber-optic sensing in single- and multimode optical fiber using intrinsic Rayleigh backscatter.  Results from sensing lengths greater than 1 km of optical fiber with spatial resolutions better than 10 cm are reported.

 

“High-Accuracy Fiber-Optic Shape Sensing”

R. G. Duncan et al., “High-accuracy Fiber-Optic Shape Sensing,” 14th Int. Symp.: Smart Structures and Materials & Nondestructive Evaluation and Health Monitoring, San Diego, CA 2007,  pp. 65301S-11.

We describe the results of a study of the performance characteristics of a monolithic fiber-optic shape sensor array.

 

“Multiple Fiber Loop Strain Rosettes in a Single Fiber using High Resolution Distributed Sensing”

D. K. Gifford et al., “Multiple Fiber Loop Strain Rosettes in a Single Fiber Using High Resolution Distributed Sensing,” IEEE Sensors J., vol. 12, no. 1, pp. 55-63, Jan. 2012. 

Simple, circular loops in a single optical fiber   bonded to a metal test sample are used to form multiple strain gauge rosettes. Strain measurements are made using an Optical Backscatter Reflectometer to detect changes in the phase of the Rayleigh Scatter of the fiber with 160 µm spatial resolution along the length of the fiber.  The high spatial resolution and strain sensitivity of this technique enable highly functional fiber rosettes formed of small diameter loops of unaltered low-bend-loss optical fiber.

 

“Optical Fiber Distributed Sensing – Physical Principles and Applications”

A. Guemes et. al., “Optical Fiber Distributed Sensing – Physical Principles and  Applications,” Structural Health Monitoring, vol. 9, no. 3, pp. 233-245, May 2010.

Obtaining the strain data all along the optical fiber, with adequate spatial resolution and strain accuracy, opens new possibilities for structural tests and for structural health monitoring.  In this article, the physical principles underlying the different techniques for distributed sensing are discussed, a classification is done based on the backscattered wavelength; this is important to understand its possibilities and performances.  The field of applications of this new technology is very wide; results of the structural tests of a 40m long wind turbine blade, detecting the location and load of onset of buckling, and the results of the delamination detection in a composite plate, are presented as examples.

 

“Correlation and Keying of Rayleigh Scatter for Loss and Temperature Sensing in Parallel Optical Networks”
Froggatt, M., Soller, B., Gifford, D., & Wolfe, M. (2004, February). Correlation and keying of Rayleigh scatter for loss and temperature sensing in parallel optical networks. In Optical Fiber Communication Conference. Optical Society of America.

Using optical backscatter reflectometry to measure distributed temperature changes in parallel optical networks.