Opto-Mechanical Fiber Optic Sensors: Research, Technology, and Applications in Mechanical Sensing

344 Pages·2017·23.267 MB·English

by  Hamid Alemohammad

O P T O - M E C H A N I C A L
F I B E R O P T I C S E N S O R S
Research, Technology,
and Applications
in Mechanical Sensing
Edited by
HAMID ALEMOHAMMAD
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LIST OF CONTRIBUTORS
Hamid Alemohammad
AOMSTechnologiesInc.,Toronto,ON,Canada
Christopher Baldwin
Weatherford,Laurel,MD,UnitedStates
Lun-Kai Cheng
TNO,Delft,TheNetherlands
Xija Gu
RyersonUniversity,Toronto,ON,Canada
Neisei Hayashi
TokyoInstituteofTechnology,Yokohama,Japan
Iulian Iordachita
JohnsHopkinsUniversity,Baltimore,MD,UnitedStates
Antonio B. Lobo Ribeiro
UniversityFernandoPessoa,Porto,Portugal
Craig Lopatin
Technion-IsraelInstituteofTechnology,Haifa,Israel
Hua Lu
RyersonUniversity,Toronto,ON,Canada
Stephen J. Mihailov
NationalResearchCouncilofCanada,Ottawa,ON,Canada
Yosuke Mizuno
TokyoInstituteofTechnology,Yokohama,Japan
Kentaro Nakamura
TokyoInstituteofTechnology,Yokohama,Japan
Sven Poeggel
UniversityofLimerick,Limerick,Ireland
xii LISTOF CONTRIBUTORS
Paulo Roriz
InstituteUniversityofMaia(ISMAI),Maia,Portugal;INESCTEC,Porto,
Portugal;LABIOMEP,PortoBiomechanicsLaboratory,Porto,Portugal;
CIDESD-ISMAI,CIDESD,Maia,Portugal
Emiliano Schena
Universita` CampusBio-MedicodiRoma,Rome,Italy
Peter Martijn Toet
TNO,Delft,TheNetherlands
Daniele Tosi
NazarbayevUniversity,Astana,Kazakhstan
BIOGRAPHY
Hamid Alemohammad, PhD, PEng, is the cofounder and
CEO of AOMS Technologies Inc. Dr. Alemohammad has PhD in
Mechanical Engineering from the University of Waterloo in
Ontario, Canada. He is specialized in industrial and academic
researchonfiberopticsensorsalongwiththecommercialization
of fiber optic sensor technologies for harsh environment and
industrial sensing applications.
PREFACE
The 1960s was a turning point for the fiber optic industry
following the breakthrough discovery by Charles Kao (2009
Nobel Prize Laureate in Physics) and George Hockham from
Standard Telecommunication Laboratories in England on
reducing the loss in glass fibers by removing impurities. In the
following decade, the work conducted by scientists at Corning
and Bell Laboratories resulted in the development of a scalable
mass production process for the manufacturing of low-loss
optical fibers, which are now widely deployed to transmit
voice and data over long distances.
Optical fibers, which are a commodity for the telecommuni-
cations industry, have found their way into the sensing industry.
Inthe early days,fiberoptic sensortechnology was adopted only
by the oil and gas and defense sectors, because of the relatively
high cost of the technology. However, thanks to new advance-
mentsinthedevelopmentoflow-costoptoelectronicsystems,the
technology is finding niche markets in other industry sectors
including biomedical, environmental, transportation, structural
health monitoring, and process industries. The industrial adop-
tion of fiber optic sensors stems from unique features and tech-
nicalcapabilitiesunmatchedbyelectronicsensors;thesefeatures
include low-loss remote sensing, the ability to work in harsh
environments, immunity to electromagnetic interference, small
size, and capability of integrated and distributed sensing. The
numbersofpatentsandscholarlyarticlespublishedintheareaof
fiber optic sensing, new companies commercializing state-of-art
fiber optic sensor technologies, and research and development
(R&D) investments by renowned research centers indicate the
global growth of this technology. According to the market
research report Fiber Optic Sensors: Global Markets published by
BCC Research in 2017, the global market size for fiber optic sen-
sors is projected to reach $3.2billion by 2021 from $2.0billion in
2016witha5-yearcompoundannualgrowthrateofaround10%.
The world-class research on specialty optical fiber sensors (i.e.,
polymer fibers, photonic crystal fibers,femtosecond written fiber
xvi PREFACE
Bragg gratings, etc.) and the development of low-cost and
affordable optical fiber sensor interrogators are the primary
driversforthe adoptionofthetechnologyandemergenceofnew
use cases for fiber optic sensing.
This book relays state-of-the-art research results and
prospective advances in the field of fiber optic sensing with
emphasis on opto-mechanical sensing applications. It is a
consolidated collection of contributions by researchers in
academia, research centers, and industrial R&D departments.
The book aims at agglomerating recent research into one
single source that is accessible to a wide range of audience.
It provides a reference source for R&D engineers, scientists,
application engineers, and technical managers in industries
relevant to test and measurement and for university faculty
members, postdoctoral fellows, and graduate students prac-
ticing research in various engineering and applied science
disciplines.
Hamid Alemohammad
AOMS Technologies, Inc.
Toronto, Canada
1
OPTO-MECHANICAL MODELING
OF FIBER BRAGG GRATING
SENSORS
Hamid Alemohammad
AOMSTechnologiesInc.,Toronto,ON,Canada
1.1 Fiber Bragg Gratings
Fiber Bragg gratings (FBGs) are permanent modulations of the
index of refraction in optical fibers. An FBG with a submicrom-
eter periodic modulation of the index of refraction functions as
thefilter.WhenaBragggratingisexposedtoabroadbandspec-
trum of light, the guided light wave propagating along the opti-
cal fiber is scattered by each grating plane. As a result, parts of
the spectrum at specific wavelengths are reflected back. The
coupling between the forward and the backward propagating
modes results in a resonance condition. The resonance occurs
ataspecificwavelengthcalledtheBraggwavelength(lB).Wave-
lengths not coincident with the Bragg condition degenerate
progressively with weak reflections, whereas wavelengths close
totheresonancewavelengthdeterminedbytheBraggcondition
undergo strong reflections. Fig. 1.1 shows the spectral response
of a uniform Bragg grating. The Bragg wavelength is(cid:1)relat(cid:3)ed to
the effective propagating mode index of refraction neff and
the grating parameters, as defined in the Bragg condition [1,2]
lB ¼ 2neffL (1.1)
where L isthe grating pitch length.
Typically, the modulation of the index of refraction [Dn(z)]
alongthe fiber axis for a Bragg grating isexpressed as[3]
(cid:4) (cid:5) (cid:6)(cid:7)
2p
DnðzÞ ¼ DnðzÞ 1þnf cos L zþFðzÞ (1.2)
whereDnðzÞisthespatiallyaveragedindexchangealongthefiber,
nf is the fringe visibility, F(z) is the grating chirp determining the
Opto-MechanicalFiberOpticSensors.http://dx.doi.org/10.1016/B978-0-12-803131-5.00001-5 1
Copyright©2018ElsevierInc.Allrightsreserved.
2 Chapter 1 OPTO-MECHANICALMODELING OFFIBERBRAGGGRATINGSENSORS
y
vit
cti
e
efl
R
l l
B
Figure1.1 SpectralresponseofauniformfiberBragggrating.
variationsofthegratingpitchlengthalongthefiber,andthezdi-
rection iscoincidentwith the fiber axis.
1.2 Opto-Mechanical Properties of Optical
Fibers
Theindexofrefractioninsilica,whichisadielectricmaterial,isa
functionoftheappliedstrainandtemperature.Owingtophotoe-
lastic and thermooptic effects, strain and temperature induce
changes in the index of refraction [4]. Fig. 1.2 shows a dielectric
medium (U) exposed to temperature and strain distributions,
T(x,y,z)andei(x,y,z),respectively,inthexyzcoordinates.Theindex
T(x,y,z)&e(x,y,z)
i
W
y
x
z
Figure1.2 Dielectricmaterial undertemperatureandstraindistributions.
Chapter 1 OPTO-MECHANICALMODELINGOF FIBERBRAGGGRATINGSENSORS 3
ofrefractiontensorindielectricmaterialsintheCartesiancoordi-
natesisgivenby
2 3
n n n
xx xy xz
6 7
½n(cid:2) ¼ 4nyx nyy nyz5 (1.3)
n n n
zx zy zz
Becausethetensorissymmetric,itisrepresentedbysixelements
as follows:
2 3
n n n
1 6 5
6 7
½n(cid:2) ¼ 4n n n 5 (1.4)
6 2 4
n n n
5 4 3
The photoelastic and thermooptic effects are defined by intro-
ducing a dielectric impermeability tensor ([B]) [4],where
1
Bi ¼ n2 i ¼ 1;2;3
i (1.5)
Bi ¼ 0 i ¼ 4;5;6
By neglecting the second-order terms, the change in the imper-
meability tensor (DBi), due to the applied strain (photoelastic
effect)and temperature(thermooptic effect), is obtained by [5,6]
DBi ¼ QiDT þpijej i;j ¼ 1.6 (1.6)
where [p] is the strain-optic tensor, called Pockels’ photoelastic
constant. For anisotropic material, [p] isexpressed as
2 3
6p p p 0 0 0 7
6 11 12 12 7
6 7
6 7
6p p p 0 0 0 7
6 12 11 12 7
6 7
6 7
6p p p 0 0 0 7
6 12 12 11 7
h i 66 77
p ¼ 666 0 0 0 ðp11(cid:3)2 p12Þ 0 0 777 (1.7)
6 7
6 7
666 0 0 0 0 ðp11(cid:3)p12Þ 0 777
6 2 7
6 7
6 7
64 0 0 0 0 0 ðp11(cid:3)p12Þ75
2