The final technical report on Optical Fiber Sensors for Materials and Structures Characterization, covering the period August 1990 through August 1991 is presented. Research programs in the following technical areas are described; sapphire optical fiber sensors; vibration analysis using two-mode elliptical core fibers and sensors; extrinsic Fabry-Perot interferometer development; and coatings for fluorescent-based sensor. Research progress in each of these areas was substantial, as evidenced by the technical publications which are included as appendices

Claus, R. O.

Lindner, D. K.

English

NASA Technical Reports Server

NASA-CR-194090
FINAL REPORT
NASA GRANT NAG 1-1176
/
f"
Optical Fiber Sensors for Materials and
Characterization
Structures
SUBMITTED TO: Dr. Robert S. Rogowski
Mail Stop 231
NASA Langley Research Center
Hampton, VA 23665
Dr. D.K. Lindner/Dr. R.O. Claus
Fiber & Electro-Optics Research Center
Virginia Tech
Blacksburg, VA 24061
September 1991
(NASA-CR-194090) OPTICAL FIBER
SENSORS FOR MATERIALS ANO
STRUCTURES CHARACTERIZATION Final
Report (Virginia Polytechnic Inst.
and State Univ.) 7 p
N9_-13353
Uncl as
G3/74 0182143
https://ntrs.nasa.gov/search.jsp?R=19940008880 2020-06-16T21:52:19+00:00Z
Contents
1. Discussion of Research Progress
2. Journal Papers
3. Conference Papers
DISCUSSIONOF RESEARCHPROGRESS
This is the final technical report for NASA contract NAG 1-1176
titled, "Optical Fiber Sensors for Materials and Structures
Characterization." During the period August 1990 through August
1991, three graduate research assistants and two electrical
engineering faculty (Lindner and Claus) within the Fiber & Electro-
Optics Research Center at Virginia Tech worked on this research
program in three specific technical areas which are described
briefly below. Research progress in each of these areas was
substantial, as evidenced by the technical publications which are
included in this report as appendices.
SAPPHIRE OPTICAL FIBERSENSORS
The first major area of activity on this grant program was the
investigation of sapphire fiber-based sensors for the evaluation of
material parameters. Sapphire fiber sensors exist commercially but
only use sapphire rod waveguides as bulk transmission elements to
effectively look inside materials or structural systems. During the
past year, our group has developed sapphire fiber-based
interferometric systems which allow the very sensitive
quantitative measurement of strain, temperature, vibration,
displacements and ultrasonic waves at high temperatures. Tests
indicate that the sapphire elements are capable of withstanding
temperatures in excess of 1700oc, and packaging limitations alone
restrict their temperature at this time. We feel that the
development of these high temperature fiber interferometers is a
major step toward the implementation of highly sensitive fiber
sensor systems for the analysis of advanced aerospace materials
and combustion processes. Several publications based on NASA
sponsored work are listed in the appendices.
VIBRATION ANALYSIS USING TWO-MODE ELLIPTICAL CORE FIBERS AND
SENSORS
A second major area of emphasis in this grant program has been the
application of "modal domain" optical fiber sensors for vibration
analysis. Modal domain sensors were first investigated with NASA
funding several years ago, and they have evolved into sensors which
use elliptical core fiber designed to support tWO propagating modes.
These two mode elliptical core fiber sensors have been shown to be
particularly advantageous for the monitoring of vibration in
structures, and large space structures have been of primary concern
here.
This year, we have made two significant steps in this area. First,
we have demonstrated that by tapering the geometry of the two
mode e-core fibers, we can weight the sensitivity of the fiber
sensor along its length. This potentially allows the implementation
of a wide range of variable sensitivity sensors for environmental
field analysis. We have specifically used these weighted sensors to
detect certain vibrational mode shape amplitudes in vibrating
structures while suppressing information from other modes.
Further, we have written gratings in these fibers and have used
weightings in the gratings to also achieve weighted fiber sensor
performance.
EXTRINSIC FABRY-PEROT INTERFEROMETER DEVELOPMENT
The third area of emphasis in this program has been the development
of extrinsic Fabry-Perot interferometric (EFPI) sensors for the
measurement of strain and temperature. Specifically in this area,
we have provided to NASA Langley descriptions of these sensors and
the required support hardware with the understanding that such
sensors may be candidates for measurements on the instrumentation
platform to be included in a shuttle test program in 1994. EFPi
sensor hardware would be prototyped and flight qualified in the
future to support this measurement system requirement.
COATINGS FOR FLORESCENT-BASED SENSOR
Finally, we have worked with Dr. Claudio Eggalon at NASA Langley to
attempt to coat optical fiber waveguides with special florescent
materials which he has provided to us. The initial tests for this
work have not proven to be conclusive and we anticipate additional
coating tests on the optical fiber draw tower in the near future.
The following are journal papers and conference papers which relate
to work supported directly by the NASA Langley Research Center
during the past year. Over the past eleven years, and as part of this
continuing grant program, NASA funds have supported seventeen
separate graduate students, fourteen of them U.S. citizens, in the
area of optical fiber sensor systems for materials analysis.
Further, the Fiber & Electro-Optics Research Center has published
more than two hundred related conference and journal papers in this
area, most of which have been related in part to work which has
been supported by NASA.
2. Journal Papers
"Polarimetric Analysis of Two-Mode, Elliptical-Core Optical Fibers," Optics
Letters, Vol. 16, No. 7, April 1, 1991, pp. 464-466, with A.M. Vengsarkar, B.R.
Fogg, and K.A. Murphy
"Demodulation Techniques for Two-Mode Elliptical-Core Fiber Sensors,"
Electronics Letters, Vol. 27, No. 16, August 1, 1991, pp. 1454-1456.
"Quadrature Phase-Shifted, Extrinsic Fabry-Perot Optical Fiber Sensors," Optics
Letters, Vol. 16, No. 4, February 1991, pp. 173-275, with K. Murphy, M.
Gunther and A. Vengsarkar.
"Elliptical-Core, Dual-Mode Optical Fiber Strain and Vibration Sensors for
Composite Material Laminates," J. CompositeTech., Vol. 13, No. 1, Spring 1991,
pp. 29-35, with K. Murphy, M. Miller and A. Vengsarkar.
"Fiber Optic Sensors Using High Resolution Optical Time Domain Instrumentation
Systems, B. Zimmermann, D. Kapp, R. Claus and K. Murphy, Journal of
Lightwave Technology, Vol 8, No. 9, September 1990, pp. 1273-1277.
"Elliptical-Core, Two-Mode, Optical Fiber Sensor Implementation Methods, K.
Murphy, W. Miller, A. Vengsarkar, and R.O. Claus, J. Lightwave Technology,
Vol. 8, No. 11, November 1990, pp. 1688-1697.
"Direct Numerical Analysis of Dual-Mode Eliptical Core Optical Fiber, K. Shaw,
A. Vengsarkar, R. Claus, Optics Letters, Vol. 16, No. 3, February 1991, pp. 135-
137.
"Miniaturized Fiber Optic Michelson-Type Interferometric Sensors, K. Murphy, M.
Miller, T. Tran, A. Vengsarkar and R. Claus, Applied Optics, Submitted 2/90.
"Stable, Phase-Modulated, Fiber Optic Sensors for Senior EE Laboratory
Curricula, A. Vengsarkar, K. Murphy, R. Claus, IEEE Trans. on Education,
Submitted 2/90.
"Modal Dependence of the Photoelastic Coefficient in Multimode, Step-Index
Optical Fiber Time Domain Systems, A. Vengsarkar, D. Thomas, B. Zimmermann,
and R. Claus, IEEE Photon Tech. Ltrs, Vol. 2, No. 11, November 1990, pp. 812-
815.
3. Conference Papers
Measurement and Control of Flexible Structures Using Distributed Sensors, D.
Lindner, Reichard, Baumann, IEEE Conference on Decision and Control, Honolulu,
HI, 1990.
Virginia Tech Fiber Optic Sensor-Based Smart Materials and Structures Overview,
R.O. Claus, SPIE (San Jose) September 1990.
Theoretical Analysis of Two-Mode, Elliptical-Core Optical Fiber Sensors, J. Shaw, A.
Vengsarkar, and R.O. Claus, SPIE, (San Jose) September 1990.
FiberOpticSensorfor SimultaneousMeasurementof StrainandTemperature,A.
Vengsarkar,W. Michie,L. Jankovic,B. Culshaw,R.Claus,SPIE(SanJose)
September1990.
RecentProgressinHigh ResolutionOpticalFiberTimeDomainMethodsandits Impact
onDynamicEnvironmentSensingApplications,B. Zimmermann,D. Thomas,R.
Claus,SPIE(SanJose)September1990.
IdentificationandControlof aFlexibleBeamUsingModalDomainSensor,D. Cox,
D. Lindner,C. Furness,S.Bingulac,SPIE,(SanJose),September1990.
GenerationandDetectionof UltrasonicStressWavesin MaterialsUsingEmbedded
OpticalFibers,C. Thompson,W. Miller, R. Claus,SPIE(SanJose)September1990.
High TemperatureSensingApplicationsof Silica and Sapphire Optical Fibers, K.
Murphy, C. Koob, A. Plante, S. Desu, and R. Claus, (San Jose) September 1990.
Vibration Sensing in Flexible Structures Using a Distributed-Effect Modal Domain
Optical Fiber Sensor, K.M. Reichard, D.K. Lindner and R.O. Claus, accepted for
the SPIE Conference on Structures Sensing and Control/Controls for Optical
Systems, Orlando, FL, April, 1991.
Distributed-Effect Optical Fiber Sensors for Plates and Trusses, K.M. Reichard,
D.K. Lindner, Proceedings of the SPIE/AIAA Conference on Aerospace
Sensors/Sensors and Sensor Integration, Vol. 1480, Orlando, FL., April 1991, pp.
115-126.
Modal Domain Optical Fiber Sensors for Vibration Sensing in Large Flexible Truss
Structures, D.K. Lindner, R.O. Claus and H. Cudney, Proceedings of the 4th
Annual NASA/DoD Technology Conference, Orlando, FL, November 5-7, 1990,
pp. 280-294.


Optical fiber sensors for materials and structures characterization

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