OpticalFibreSensors
FundamentalsforDevelopment ofOptimizedDevices
Editedby
IgnacioDelVillar IgnacioR.Matias
IEEEPressSeriesonSensors
VladimirLumelsky,SeriesEditor
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LibraryofCongressCataloging-in-PublicationData:
Names:DelVillar,Ignacio,1978-editor.|Matias,IgnacioR.,1966–editor.|InstituteofElectricalandElectronicsEngineers.
Title:Opticalfibresensors:fundamentalsfordevelopmentofoptimized devices/editedbyIgnacioDelVillar,IgnacioR. Matias.
Othertitles:Opticalfibresensors(JohnWiley&Sons)
Description:Hoboken,NewJersey:Wiley-IEEEPress,[2021]|Series:IEEE Pressseriesonsensors|Includesbibliographicalreferencesandindex.
Identifiers:LCCN2020020787(print)|LCCN2020020788(ebook)|ISBN 9781119534761(cloth)|ISBN9781119534778(adobepdf)|ISBN 9781119534792(epub)
Subjects:LCSH:Opticalfibredetectors.
Classification:LCCTA1815.O6962021(print)|LCCTA1815(ebook)|DDC 621.36/92–dc23
LCrecordavailableathttps://lccn.loc.gov/2020020787
LCebookrecordavailableathttps://lccn.loc.gov/2020020788
CoverDesign:Wiley
CoverImage:©MirageC/GettyImages
Setin9.5/12.5ptSTIXTwoTextbySPiGlobal,Pondicherry,India
PrintedintheUnitedStatesofAmerica.
Contents
ListofContributors xv
Acknowledgment xix
AbouttheEditors xxi
1Introduction 1 IgnacioR.MatiasandIgnacioDelVillar References 14
2PropagationofLightThroughOpticalFibre 17 IgnacioDelVillar
2.1GeometricOptics 17
2.2WaveTheory 22
2.2.1ScalarAnalysis 23
2.2.2VectorialAnalysis 26
2.3FibreLossesandDispersion 32
2.4PropagationinMicrostructuredOpticalFibre 35
2.5PropagationinSpecialtyOpticalFibresFocusedonSensing 37
2.6Conclusion 45 References 46
3OpticalFibreSensorSet-UpElements 49 MinghongYangandDajuanLyu
3.1Introduction 49
3.2LightSources 50
3.2.1Light-EmittingDiodes 52
3.2.1.1SurfaceLight-EmittingDiode 52
3.2.1.2SideLight-EmittingDiode 52
3.2.2LaserDiode 53
3.2.2.1Single-ModeLaserDiodeStructure 54
3.2.2.2QuantumWellLaserDiode 56
3.2.3SuperluminescentDiodes(SLD) 56
3.2.4AmplifiedSpontaneousEmissionSources 59
3.2.5NarrowLineBroadbandSweepSource 62
3.2.6BroadbandSources 62
3.3OpticalDetectors 63
3.3.1BasicPrinciplesofOpticalDetectors 64
3.3.1.1PNPhotodetector 64
3.3.1.2PINPhotodetector 65
3.3.1.3AvalanchePhotodiode(APD) 66
3.3.2MainCharacteristicsofOpticalDetectors 66
3.3.2.1OperatingWavelengthRangeandCut-OffWavelength 66
3.3.2.2QuantumEfficiencyandResponsiveness 67
3.3.2.3ResponseTime 68
3.3.2.4MaterialsandStructuresofSemiconductorPhotodiodes 69
3.3.3OpticalSpectrometers 70
3.4LightCouplingTechnology 71
3.4.1CouplingofFibreandLightSource 71
3.4.1.1CouplingofSemiconductorLasersandOpticalFibres 71
3.4.1.2CouplingLossofSemiconductorLight-EmittingDiodesandOptical Fibres 72
3.4.2MultimodeFibreCoupledThroughLens 72
3.4.3DirectCouplingofFibreandFibre 73
3.5Fibre-OpticDevice 74
3.5.1FibreCoupler 74
3.5.2OpticalIsolator 74
3.5.3OpticalCirculator 76
3.5.4FibreAttenuator 76
3.5.5FibrePolarizer 76
3.5.6OpticalSwitch 77
3.6OpticalModulationandInterrogationofOpticalFibre-Optic Sensors 77
3.6.1Intensity-ModulatedOpticalFibreSensingTechnology 78
3.6.1.1ReflectiveIntensityModulationSensor 78
3.6.1.2TransmissiveIntensityModulationSensor 80
3.6.1.3LightMode(Microbend)IntensityModulationSensor 80
3.6.1.4RefractiveIndexIntensity-ModulatedFibre-OpticSensor 80
3.6.2WavelengthModulationOpticalFibreSensingTechnology 81
3.6.2.1DirectDemodulationSystem 81
3.6.2.2NarrowBandLaserScanningSystem 82
3.6.2.3BroadbandSourceFilterScanningSystem 83
3.6.2.4LinearSidebandFilteringMethod 84
3.6.2.5InterferenceDemodulationSystem 84
3.6.3PhaseModulationOpticalFibreSensingTechnology 86 References 87
4BasicDetectionTechniques 91 DanieleTosiandCarloMolardi
4.1Introduction 91
4.2OverviewofInterrogationMethods 93
4.3Intensity-BasedSensors 97
4.3.1Macrobending 97
4.3.2In-LineFibreCoupling 99
4.3.3BifurcatedFibreBundle 100
4.3.4SmartphoneSensors 100
4.4Polarization-BasedSensors 102
4.4.1PressureandForceDetection 102
4.4.2LossyModeResonanceforRefractiveIndexSensing 104
4.5Fibre-OpticInterferometers 105
4.5.1Fabry–PérotInterferometer(FPI)-BasedFibreSensors 106
4.5.1.1ExtrinsicFPIforPressureSensing 107
4.5.1.2In-LineFPIforTemperatureSensing 108
4.5.2Mach–ZehnderInterferometer(MZI)-BasedFibreSensors 109
4.5.3Single-Multi-SingleMode(SMS)Interferometer-BasedFibre Sensors 109
4.6Grating-BasedSensors 111
4.6.1FibreBraggGrating(FBG) 111
4.6.2FBGArrays 113
4.6.3TiltedandChirpedFBG 115
4.6.4Long-PeriodGrating(LPG) 117
4.6.5FBGFabrication 118
4.7Conclusions 121 References 121
5StructuralHealthMonitoringUsingDistributed Fibre-OpticSensors 125 AlaynLoayssa
5.1Introduction 125
5.2FundamentalsofDistributedFibre-OpticSensors 126
5.2.1RamanDTS 128
5.2.2BrillouinDTSS 129
5.3DFOSinCivilandGeotechnicalEngineering 130
5.3.1Bridges 133
5.3.2Tunnels 134
5.3.3GeotechnicalStructures 137
5.4DFOSinHydraulicStructures 141
5.5DFOSintheElectricGrid 143
5.6Conclusions 145
References 146
6DistributedSensorsintheOilandGasIndustry 151
ArthurH.Hartog
6.1TheLateLifeCycleofaHydrocarbonMolecule 153
6.1.1Upstream 154
6.1.1.1Exploration 154
6.1.1.2WellConstruction 155
6.1.1.3FormationandReservoirEvaluation 157
6.1.1.4Production 158
6.1.1.5ProductionofMethaneHydrates 159
6.1.1.6WellAbandonment 160
6.1.2Midstream:Transportation 160
6.1.3Downstream:RefineryandDistribution 161
6.2ChallengesintheApplicationofOpticalFibrestotheHydrocarbon 161
6.2.1Conditions 161
6.2.2ConveyanceMethods 162
6.2.2.1TemporaryInstallations(InterventionServices) 163
6.2.2.2PermanentFibreInstallations 163
6.2.3FibreReliability 165
6.2.4FibreTypes 166
6.3ApplicationsandTake-Up 168
6.3.1Steam-AssistedRecovery;SAGD 168
6.3.2FlowAllocation:ConventionalWells 171
6.3.3InjectorMonitoring 174
6.3.4ThermalTracerTechniques 175
6.3.5WaterFlowBetweenWells 176
6.3.6Gas-LiftValves 176
6.3.7VerticalSeismicProfiling(VSP) 177
6.3.8HydraulicFracturingMonitoring(HFM) 184
6.3.9SandProduction 185
6.4Summary 186 References 186
7BiomechanicalSensors 193
CiceroMartelli,JeanCarlosCardozodaSilva,AlessandraKalinowski, JoséRodolfoGalvão,andTalitaPaes
7.1OpticalFibreSensorsinBiomechanics:IntroductionandReview 193
7.2OpticalFibreSensors:FromExperimentalPhantomsto InVivo Applications 198
7.2.1ExperimentalPhantomsandModels 198
7.2.1.1Joints 199
7.2.1.2BonesandMuscles 199
7.2.1.3Teeth,LowerJaw(Mandible),andUpperJaw(Maxilla) 200
7.2.1.4ProsthesisandExtracorporealDevices 200
7.2.1.5SoleandInsoles 201
7.2.1.6SmartFabrics 201
7.2.1.7BloodVessels 202
7.2.1.8RespiratoryMonitoring 203
7.2.2 InVitro 203
7.2.3 ExVivo 204
7.2.3.1Joints 204
7.2.3.2BonesandMuscles 205
7.2.3.3Teeth,LowerJaw(Mandible),andUpperJaw(Maxilla) 205
7.2.3.4BloodVessels 205
7.2.3.5MechanicalPropertiesofTissues 207
7.2.4 InVivo 207
7.2.4.1Joints 207
7.2.4.2BonesandMuscles 207
7.2.4.3Teeth,LowerJaw(Mandible)andUpperJaw(Maxilla) 208
7.2.4.4BloodVessels 208
7.2.4.5RespiratoryMonitoring 208
7.2.5 InSitu 208
7.2.5.1Joints 209
7.2.5.2BonesandMuscles 209
7.2.5.3ProsthesesandExtracorporealDevices 210
7.2.5.4SolesandInsoles 210
7.2.5.5CardiacMonitoring 211
7.2.5.6RespiratoryMonitoring 211
7.3FBGSensorsIntegratedintoMechanicalSystems 213
7.3.1FBGSensorsGluedwithPolymer 214
x Contents
7.3.2Polymer-IntegratedFBGSensor 215
7.3.3SmartFibreReinforcedPolymer(SFRP) 218
7.4FuturePerspective 222 Acknowledgment 223 References 224
8OpticalFibreChemicalSensors 239 T.HienNguyenandTongSun
8.1Introduction 239
8.2PrinciplesandMechanismsofFibre-Optic-BasedChemical Sensing 240
8.2.1PrincipleofChemicalSensorResponse 240
8.2.2Absorption-BasedSensors 242
8.2.3Luminescence-BasedSensors 243
8.2.4SurfacePlasmonResonance(SPR)-BasedSensors 245
8.3SensorDesignandApplications 247
8.3.1OpticalFibrepHSensors 247
8.3.1.1PrincipleofFluorescence-BasedpHMeasurements 248
8.3.1.2pHSensorDesign 249
8.3.1.3Set-UpofapHSensorSystem 253
8.3.1.4EvaluationofthepHSensorSystems 254
8.3.1.5Comments 260
8.3.2OpticalFibreMercurySensor 261
8.3.2.1SensorDesignandMechanism 262
8.3.2.2EvaluationoftheMercurySensorSystem 265
8.3.2.3Comments 271
8.3.3OpticalFibreCocaineSensor 271
8.3.3.1SensingMethodology 272
8.3.3.2DesignandFabricationofaCocaineSensorSystem 273
8.3.3.3EvaluationoftheCocaineSensorSystem 275
8.3.3.4Comments 280
8.4ConclusionsandFutureOutlook 281 Acknowledgements 282 References 282
9ApplicationofNanotechnologytoOpticalFibreSensors:Recent AdvancementsandNewTrends 289 ArmandoRicciardi,MarcoConsales,MarcoPisco,andAndreaCusano
9.1Introduction 289
9.2AViewBack 292
9.3NanofabricationTechniquesontheFibreTipforBiochemical Applications 293
9.3.1DirectApproaches 294
9.3.2IndirectApproaches 301
9.3.3Self-Assembly 305
9.3.4SmartMaterialsIntegration 307
9.4NanofabricationTechniquesontheFibreTipforOptomechanical Applications 309
9.5Conclusions 317 References 320
10FromRefractometrytoBiosensingwithOpticalFibres 331 FrancescoChiavaioli,AmbraGiannetti,andFrancescoBaldini
10.1BasicSensingConceptsandParametersforOFSs 332
10.1.1ParametersofGeneralInterest 335
10.1.1.1Uncertainty 335
10.1.1.2AccuracyandPrecision 335
10.1.1.3SensorDriftandFluctuations 336
10.1.1.4Repeatability 336
10.1.1.5Reproducibility 336
10.1.1.6ResponseTime 336
10.1.2ParametersRelatedtoVolumeRISensing 337
10.1.2.1RefractiveIndexSensitivity 337
10.1.2.2Resolution 338
10.1.2.3FigureofMerit(FOM) 339
10.1.3ParametersRelatedtoSurfaceRISensing 339
10.1.3.1SensorgramandCalibrationCurve 340
10.1.3.2LimitofDetection(LOD)andLimitofQuantification(LOQ) 341
10.1.3.3Specificity(orSelectivity) 345
10.1.3.4Regeneration(orReusability) 345
10.2OpticalFibreRefractometers 347
10.2.1OpticalInterferometers 348
10.2.2Grating-BasedStructures 348
10.2.3OtherResonance-BasedStructures 350
10.3OpticalFibreBiosensors 352
10.3.1Immuno-BasedBiosensors 353
10.3.2Oligonucleotide-BasedBiosensors 354
10.3.3WholeCell/Microorganism-BasedBiosensors 357
10.4FibreOpticsTowardsAdvancedDiagnosticsandFuture Perspectives 360 References 361
11Humidity,Gas,andVolatileOrganicCompoundSensors 367
DiegoLopez-TorresandCésarElosua
11.1Introduction 367
11.2OpticalFibreSensorSpecificFeaturesforGasandVOCDetection 368
11.3SensingMaterials 370
11.3.1OrganicChemicalDyes 370
11.3.2Metal–OrganicFramework(MOF)Materials 372
11.3.3MetallicOxides 374
11.3.4Graphene 378
11.4DetectionofSingleGases 379
11.5RelativeHumidityMeasurement 383
11.6DevicesforVOCSensingandIdentification 384
11.7ArtificialSystemsforComplexMixturesofVOCs:Optoelectronic Noses 387
11.8Conclusions 391 References 392
12InteractionofLightwithMatterinOpticalFibreSensors: ABiomedicalEngineeringPerspective 399 SillasHadjiloucas
12.1Introduction 399
12.2EnergyContentinLightandItsEffectinChemicalProcesses 399
12.3RelevanceofWien’sLawtoPhysicochemicalProcesses 402
12.4AbsorptionofLightMolecules 403
12.5TheRoleofElectronSpinandStateMultiplicityinSpectroscopy 404
12.6MolecularOrbitals,BondConjugation,andPhotoisomerization 406
12.7De-excitationProcessesThroughCompetingPathways:TheirEffecton LifetimesandQuantumYield 407
12.8EnergyLevelDiagramsandVibrationalSublevels 412
12.9DistinctionBetweenAbsorptionandActionSpectra 413
12.10LightScatteringProcesses 414
12.10.1ElasticScattering 414
12.10.2InelasticScattering 416
12.11InductionofNon-linearOpticalProcesses 418
12.12ConcentratingFieldstoMaximizeEnergyExchangeintheMeasurement ProcessUsingSlowLight 419
12.12.1SlowLightUsingAtomicResonancesandElectromagneticallyInduced Transparency 419
12.12.2SlowLightUsingPhotonicResonances 424
12.13FieldEnhancementandImprovedSensitivityThroughWhispering GalleryModeStructures 427
12.14EmergentTechnologicalTrendsFacilitatingMulti-parametric InteractionsofLightwithMatter 429
12.14.1IntegrationofOpticalFibreswithMicrofluidicDevicesandMEMS 429
12.14.2Pump–ProbeSpectroscopy 430
12.15ProspectsofMolecularControlUsingFemtosecondFibreLasers 430
12.15.1FemtosecondPulseShaping 430
12.15.2NewOpportunitiesforCoherentControlofMolecularProcesses 432
12.15.3DevelopmentsinEvolutionaryAlgorithmsforMolecularControl 434 References 436
13DetectioninHarshEnvironments 441
KamilKosielandMateusz Śmietana
13.1Introduction 441
13.2OpticalFibreSensorsforHarshEnvironments 442
13.3NeedforHarshEnvironmentSensingBasedonOpticalFibres 443
13.4GeneralRequirementsforHarshEnvironmentOFSs 449
13.5SilicaGlassOpticalFibresforHarshEnvironmentSensing 451
13.6PolymerOpticalFibresforHarshEnvironmentSensing 461
13.7ChalcogenideGlassandPolycrystallineSilverHalideOpticalFibresfor HarshEnvironmentSensing 464
13.8MonocrystallineSapphireOpticalFibresforHarshEnvironment Sensing 467
13.9FutureTrendsinOpticalFibreSensing 469 References 470
14Fibre-OpticSensing:PastReflectionsandFutureProspects 477
BrianCulshawandMarcoN.Petrovich
14.1IntroductoryComments 477
14.2ReflectionsonAchievementstoDate 478
14.3Photonics:HowIsItChanging? 484
14.4SomeFutureSpeculation 486
14.4.1PhotonicIntegratedandPlasmonicCircuits 487
14.4.2MetamaterialsinSensing 490
14.4.3MoreVariationsontheNanoStory 492
14.4.4ImprovingtheSignal-to-NoiseRatio 493
14.4.5QuantumSensing,Entanglement,andtheLike 494
14.4.6TheManyProspectsinFibreDesignandFabrication 495
14.4.7TechnologiesOtherthanPhotonics 500
14.4.8SocietalAspirationsinSensorTechnology 501
14.4.9TheFutureandaQuickLookattheSensingAlternatives 501
xiv Contents
14.4.10SoWhatHasFibreSensingAchievedtoDate 503 14.5ConcludingObservations 504 References 504
Index 511
ListofContributors
FrancescoBaldini
InstituteofAppliedPhysics “Nello
Carrara” (IFAC)
NationalResearchCouncil(CNR)
Florence Italy
FrancescoChiavaioli
InstituteofAppliedPhysics “Nello
Carrara” (IFAC)
NationalResearchCouncil(CNR)
Florence Italy
MarcoConsales OptoelectronicsGroup DepartmentofEngineering UniversityofSannio Benevento
Italy
BrianCulshaw DepartmentofElectronicand ElectricalEngineering UniversityofStrathclyd,Glasgow Scotland,UK
AndreaCusano OptoelectronicsGroup DepartmentofEngineering UniversityofSannio
Benevento
Italy
JeanCarlosCardozodaSilva GraduatePrograminElectricaland ComputerEngineering FederalUniversityofTechnology -ParanáBrazil
IgnacioDelVillar DepartmentofElectrical,Electronic andCommunicationsEngineering PublicUniversityofNavarre
Pamplona
Spain
CésarElosua DepartmentofElectrical,Electronic andCommunicationsEngineering PublicUniversityofNavarre
Pamplona
Spain
JoséRodolfoGalvão GraduatePrograminElectricaland ComputerEngineering FederalUniversityofTechnology -ParanáBrazill
AmbraGiannetti InstituteofAppliedPhysics “Nello Carrara” (IFAC) NationalResearchCouncil(CNR) Florence,Italy
SillasHadjiloucas DepartmentofBiomedicalEngineering UniversityofReading Reading,UK
ArthurH.Hartog WorthyPhotonicsLtd Winchester,UK
T.HienNguyen PhotonicsandInstrumentation ResearchCentre CityUniversityofLondon London,UK
AlessandraKalinowski GraduatePrograminElectricaland ComputerEngineering FederalUniversityofTechnology -ParanáBrazil
KamilKosiel ŁukasiewiczResearchNetwork –InstituteofElectronTechnology Al.Lotników32/46,02-668Warsaw Poland
AlaynLoayssa DepartmentofElectrical,Electronic andCommunicationsEngineering PublicUniversityofNavarre Pamplona,Spain
DiegoLopez-Torres DepartmentofElectrical,Electronic andCommunicationsEngineering, PublicUniversityofNavarre, Pamplona,Spain
DajuanLyu NationalEngineeringLaboratoryfor FibreOpticSensingTechnology (NEL-FOST) WuhanUniversityofTechnology Wuhan,China
CiceroMartelli GraduatePrograminElectricaland ComputerEngineering FederalUniversityofTechnology -ParanáBrazil
IgnacioR.Matias InstituteofSmartCities PublicUniversityofNavarre Pamplona,Spain
CarloMolardi SchoolofEngineering NazarbayevUniversity Astana Kazakhstan
TalitaPaes GraduatePrograminElectricaland ComputerEngineering FederalUniversityofTechnology -ParanáBrazil xvi ListofContributors
MarcoN.Petrovich
OptoelectronicsResearchCentre UniversityofSouthampton Southampton,UK
MarcoPisco
OptoelectronicsGroup DepartmentofEngineering UniversityofSannio Benevento,Italy
ArmandoRicciardi
OptoelectronicsGroup DepartmentofEngineering UniversityofSannio Benevento,Italy
Mateusz Śmietana InstituteofMicroelectronicsand Optoelectronics WarsawUniversityofTechnology Koszykowa Warsaw,Poland
TongSun PhotonicsandInstrumentation ResearchCentre CityUniversityofLondon London,UK
DanieleTosi SchoolofEngineering,Nazarbayev University,Astana,Kazakhstan and LaboratoryofBiosensorsand Bioinstruments NationalLaboratoryAstana Astana,Kazakhstan
MinghongYang
NationalEngineeringLaboratory forFibreOpticSensingTechnology (NEL-FOST),WuhanUniversityof Technology Wuhan,China ListofContributors
Acknowledgment
Aseditors,wewouldliketoexpressourgratitudetoallthemembersof Wiley-IEEEPressfortheirassistanceandhelp.
Alsospecialthankstothewonderfulteamofauthorsthathavewrittenthechaptersofthebook.ToourcollaboratorsinthePublicUniversityofNavarra:Alayn Loayssa,DiegoLópez,andCésarElosua,wemustaddalistofprestigiousauthors thatcovermultiplecountriesallovertheworld:MinghongYangandDajuanLyu, fromtheNationalEngineeringLaboratoryforFibreOpticSensingTechnology (NEL-FOST)WuhanUniversityofTechnology,Wuhan(China);DanieleTosi andCarloMolardi,fromtheNazarbayevUniversity,SchoolofEngineering, Astana(Kazakhstan);ArthurH.Hartog,fromtheWorthyPhotonicsLtd,Winchester(UK);CiceroMartelli,JeanCarlosCardozodaSilva,AlessandraKalinowski,JoséRodolfoGalvão,andTalitaPaes,fromUniversidadeTecnológica FederaldoParaná(Brasil);T.HienNguyenandTongSun,fromthePhotonics andInstrumentationResearchCentre,City,UniversityofLondon(UK);Armando Ricciardi,MarcoConsales,MarcoPisco,andAndreaCusano,fromtheOptoelectronicsGroup,DepartmentofEngineering,UniversityofSannio,(Italy);FrancescoChiavaioli,AmbraGiannetti,andFrancescoBaldini,fromtheInstituteof AppliedPhysics ‘NelloCarrara’ (IFAC),SestoFiorentino(Italy);SillasHadjiloucas,fromtheDepartmentofBiomedicalEngineering,UniversityofReading (UK);KamilKosielandMateusz Śmietana,respectivelyfromthe Łukasiewicz ResearchNetwork-InstytutTechnologiiElektronowejinWarsaw(Poland)and fromtheInstituteofMicroelectronicsandOptoelectronicsintheWarsawUniversityofTechnology(Poland);MarcoN.Petrovich,fromtheUniversityofStrathclyde,RoyalCollegeBuilding,Glasgow,Scotland,(UK);andBrianCulshaw, fromtheOptoelectronicsResearchCentre,UniversityofSouthampton,(UK).
Wewouldlikealsotothankourfamiliesandfriends,becausewithouttheirsupportthisprojectwouldnothavebeenpossible.
xx Acknowledgment
Finally,justasmembersofthisopticalfibresensorcommunity,wewantto thankthededicationtoallthosewhopioneeredthismorethanhalfacentury agoandtothosewhowillcontinuetodoso,becausethisroadismadebywalking and,fortunately,thegoaliseverycloser.
AbouttheEditors
IgnacioDelVillar,PhD,isanAssociateProfessorintheElectrical,Electronicand CommunicationsEngineeringDepartmentatthePublicUniversityofNavarra, Spain,whereheteachesonelectronicsandindustrialcommunications.Heisa memberoftheIEEEandanAssociateEditorofdifferentjournals.Inaddition, hehasparticipatedinmultipleresearchprojectsandco-authoredmorethan 150papers,conferences,andbookchaptersrelatedtofibre-opticsensors.
IgnacioR.Matias,PhD,istheScientificDirectoroftheInstituteofSmartCities andProfessoroftheElectrical,ElectronicandCommunicationsDepartmentatthe PublicUniversityofNavarra,Spain.HewasoneoftheAssociateEditorswho foundedthe IEEESensorsJournal,promotingfibre-opticsensorssincethen throughconferences,specialissues,awards,books,etc.Hehasco-authoredmore than500bookchapters,journalandconferencepapersrelatedtoopticalfibresensors.Heiscurrentlymember-at-largeattheIEEESensorsCouncilAdCom.
Introduction IgnacioR.Matias1 andIgnacioDelVillar2
1 InstituteofSmartCities,PublicUniversityofNavarre,Pamplona,Spain
2 DepartmentofElectrical,ElectronicandCommunicationsEngineering,PublicUniversityofNavarre, Pamplona,Spain
Theopticaltelegraph,inventedin1791byClaudeChappe,consistedofanetworkofstationsthatallowedthetransmissionofinformationataspeedofone symbolintwominutesbetweenParisan dLille(i.e.230km)[1].Eachstation monitored,withtheaidofatelescope,t hecharacterthatwasrepresentedwith awoodensemaphoreintheprevioussta tion.Thissystemwaswidelyusedfor about50yearsbecauseitwasmuchfasterthansendingmessagesbyletter,but itrequireddirectvisionbetweeneachc oupleofconsecutivestations.Consequently,badweather,orsimplytheni ght,preventedits utilization.These arethemainreasonswhywiththeinventionoftheelectricaltelegraph,a systembasedonaguidedelectricalsignal,theutilizationoftheoptical telegraphcamesoontoanend.
However,inparalleltotheinventionoftheelectricaltelegraph,in1841,the pathtowardsopticalguidingwasstartedwithanimportantdiscoverybytwo Frenchresearchers,JeanDanielColladonandJacquesBabinet,whoindependentlydemonstratedthatitwaspossibletoguidelightinacurvedwaveguide [2].Colladonprovedthiswithlightraystrappedinawaterjetbytotalinternal reflection,whereasBabinetdidthesameinabentglassrod.
Anotherbreakthroughoccurredin1966,whenCharlesKao(hereceivedthe NobelPrizeinPhysicsin2009)andGeorgeHockhampublishedaworkdemonstratingthattheattenuationinopticalfibresavailableatthetimewascaused byimpurities,ratherthanfundamentalphysicaleffectssuchasscattering.They
OpticalFibreSensors:FundamentalsforDevelopmentofOptimizedDevices,FirstEdition. EditedbyIgnacioDelVillarandIgnacioR.Matias.
©2021TheInstituteofElectricalandElectronicsEngineers,Inc. Published2021byJohnWiley&Sons,Inc.
pointedoutthatfibreswithlowlosscouldbemanufacturedbyusinghigh-purity glass[3,4].ThisideawasprovedintheNorthAmericancompanyCorningin1970, withthedevelopmentofanopticalfibrewithlosseslowerthan20dB/km.Soon afterwards,in1977,losseswerereducedtosuchapointthatGeneralTelephone andElectronicscouldcarrylivetelephonetraffic,6Mbit/s,inLongBeach, California,whereastheBellSystemcouldtransmita45Mbit/sfibrelinkinthe downtownChicagophonesystem.Sincethatyearopticalfibrehasbecomethe mostwidelyusedguidedmediuminthetwentiethcentury,mainlythanksto thehugebandwidthitpresentscomparedwithotherguidedcommunication mediasuchastwistedpairandcoaxialcable.
Opticalcommunicationisthemainapplicationofopticalfibre.However,there isaseconddomainwherethisstructurecanbeused:sensors.Despitetheimpactof opticalfibreinthedomainofsensorsnotbeingasbigasincommunications,their presenceintheglobalmarketcannotbeneglected.Indeed,itisthenaturaland idealplatformintermsofintegratingthesensorinthecommunicationsystem.
Opticalfibresensors(OFSs)canbeclassifiedinmanydifferentways.Themain classificationconcernstothelocationwherethelightismodulated,existingintwo groups:extrinsicandintrinsicOFSs.Inbothcasesthereisaparameter(physical, chemical,biological,etc.)thatmodulateslight.However,thedifferenceisthatin anextrinsicOFSslightisguidedtotheinteractionregion,extrinsictotheoptical fibre,wherelightismodulated,andafterthismodulationlightiscollectedagainin theopticalwaveguide,whereasinanintrinsicOFSlightisalwaysguidedbythe opticalfibre.InFigure1.1thedifferencebetweenanintrinsicandanextrinsicOFS
isshown.Inthecaseofanextrinsicsensor,lightismodulatedoutsideofthefibre byaliquid(itspropertiesmaychangeasafunctionoftemperature,forinstance), whereasinthecaseoftheintrinsicsensor,afibrehasbeensplicedtotwoother fibres(oneinputandoneoutputfibre),whichallowsanenhancedinteractionwith theoutermedium.Inthiscase,aliquidmodulatesthelightatthesametimeitis beingtransmittedthroughthefibre.
ProbablythefirstOFSwasthefibrescope.In1930HeinrichLamm,aGerman medicalstudent,assembledabundleofopticalfibrestocarryanimage.Hispurposewastousethedeviceforobtainingimagesofinaccessiblepartsofthebody. Hetriedtopatentthedevice,butJohnLogieBairdandClarenceW.Hansellhad patentedasimilarideasomeyearsbefore.ThequalityoftheimagesthatLamm obtainedwasnotgood,butheisthefirstresearcherthatexperimentallyachieved thisbreakthroughinthehistoryofopticalsensors.Afterwards,in1954,theEnglishmanHaroldH.HopkinsandtheIndianNarinderS.Kapanypresentedresults ofbetterqualityonthesameprinciple[5].
Someyearslater,in1967,thefirsteffectivedemonstrationofafibre-opticsensor, theFotonicsensor,waspublished[6].Thedevicewasalsobasedonafibrebundle. However,thistimethearrangementwasdifferent.Someofthefibresemittedlight, andsomeothersdidnot.Thefibrebundleilluminatedasurfaceinfrontofthe fibre,andsomepartoflightwascoupledtothefibresthatdidnottransmitlight. Theamountoflightreflectedbackdependedonthedistancebetweenthefibre bundleendandthesurface.Consequently,thedevicecouldbeusedasadisplacementsensor(Figure1.2).
ThistypeofsensorwasthebasisforthecommercializationoftheMTIFotonic sensor.Inthe1980s,theMTI2000versionallowedmonitoringvibrationanddisplacement.NowadaysitisstillsoldundertheversionMTI2100,whichisthesame conceptbutwithimprovedcharacteristicssuchastheabilitytooperateincryogenic,vacuum,highpressure,orinhighmagneticfieldandharshenvironments. Theresolutionhasalsobeenimprovedfrom1nmintheMTI2000to0.25nm withtheMTI2100andfrequencyresponsefromdirect-coupled(dc)to150kHz intheMTI2000uptodc-500kHzintheMTI2100.
TheconceptusedintheFotonicsensorwasalsothebasisfordetectionofintracranialpressurebyusingasurfacethatisadiaphragmthatcanbedeformedbythe actionofpressure.Dependingonthepressure,thesurfaceisdeformed,andinthis way,thelightcoupledbacktothereceivingfibreismodulated.ThecommercializeddevicewascalledCaminoICPMonitor.
Interferometricfibresensorsemergedinthe1970s,themostsuccessfulone amongthembeingtheopticalfibregyroscope(OFG)(seeFigure1.3).Thebasic principlewasverysimple.Lightfromalaserissplitbyabeamsplitterandenters thefibreonbothends.Bothbeamsgooutofthefibreandaphotodetectorreceives them.ThankstotheSagnaceffect,bothbeamsinterfereconstructivelyand
range 1
range 2
Displacement
Figure1.2 (a–c)Fotonicsensorsetupwithafibrebundlecomposedofonetransmitting andonereceivingfibre:(a)withthesurfacetoocloseandhenceonlyasmallpartis coupledbacktothereceivingfibre;(b)withthesurfaceattheoptimalpositionforahighest coupling;and(c)withthesurfacetoofarandhenceagreatpartoflightislostandnot coupledtothereceivingfibre.(d)MTI2100diagramshowingthepowerdetectedasa functionofthedistance(themaximumisobtainedwhenthedistanceisneithertoobignor toosmall).
Figure1.3 (a)Simplifiedsetup:lightfromalaserissplitbyabeamsplitterandenters thefibreonbothends.Thetwobeamsgooutofthefibreandthephotodetectorreceives them.DuetotheSagnaceffect,bothbeamsinterfereconstructivelyanddestructively dependingontherotationspeedofthedevice.(b)Commercialopticalfibregyrowitha sizecomparabletoacoin(fromKVHwebsite).
destructivelydependingontherotationspeedofthedevice.Thefirstpublication datesfromtheyear1976[7].Sincethatmomentthedevicehasbeenimprovedwith additionalelementssuchaspolarizationcontrol,buttheinitialconceptisstill maintained.ThetruebenefitoftheOFGovertraditionalspinning-massgyrosis thatithasnomovingparts.Asaresult,OFGsarefaster,tougher,morereliable anddemandfarlessmaintenance.Thatiswhytheyhavebecomeanessentialcomponentinplatformstabilizingsystems,forexample,forlargesatelliteantennas,in missileguidance,insubseanavigation,andinaircraftstabilizationandnavigation, andahostofotherapplications[8].Itmovesabout1000millionUS$peryear accordingtoMarketsandMarkets:FibreOpticsGyroscopeMarketbySensing Axis(1,2,and3),Device(Gyrocompass,InertialMeasurementUnit,Inertial NavigationSystem,andAttitudeHeadingReferenceSystem),Application,and Geography – GlobalForecastto2022.
Basedontheacousto-opticeffect,itwaspossiblealsotodevelophydrophones, OFSsthatcoulddetectacousticwaveswhenimmersedinwater.Oneofthefirst approacheswasbasedoninterferometry[9],bycombiningthesignalstransmitted byanopticalfibrethatwasnotimmersedinwaterwiththesignalreflectedatthe endfacetofanotheropticalfibreimmersedinwater.Byexcitinganacousticwave infrontofthefibreimmersedinwater,itwaspossibletoobservevariationsinthe detectedsignal.ThoughithasnotbeenacommercialsuccesslikeOFG,thisapplicationstillattractsinterest,andtheutilizationofaFabry–Pérotcavity(i.e.acoatingontheendfacetoftheopticalfibreimmersedinwater)allowsavoidingtheuse ofthereferencefibrebecauseinthiswayaninterferometricpatternintheoptical spectrumisgenerated.ThesetupisdepictedinFigure1.4,andacommercial deviceisavailableatthecompanyPrecisionAcoustics.Itsimmunityfrom
Photodetector
Beamsplitter
Optical fibre (a) (b)
Figure1.4 OpticalsetupforaFabry–Pérothydrophone[10].OSCisoscilloscope,PD photodiode,PGpulsegenerator,PZTpiezoelectrictransducer,andTLDtunablelaserdiode. Source:ReproducedwithpermissionofElsevier.
electromagneticradiationmakesitparticularlysuitedforhigh-frequencymeasurementsinhostilefields.
Aswecansee,thispropertywasalsoincludedintheFotonicsensorandisoneof thekeyadvantagesofopticalfibresingeneral.However,inordertomakeafibre opticalsensorthefirstoptionofanenduser,moreadvantagesarerequiredcomparedwiththerestofsensorsinthemarket.InthecaseoftheOFG,thekeypropertywasthatitwasnotnecessarytousemovingparts,whichmeanslongduration andfastresponse.
AsecondOFSsuccesswasthemeasurementofcurrentandvoltagewiththeaid oftheFaradayeffect[11,12].Asanexample,ABBhasdevelopedacommercial devicecalledfibre-opticcurrentsensor(FOCS),whichcanbeusedinsteadofmagneticsystemsduetoitsexceptionalaccuracyandreliability.Itcanmeasureuni-or bidirectionalDCcurrentsofupto600kAwithanaccuracyof±0.1%ofthemeasuredvalue(Figure1.5).
Straingaugesareanotherwell-knownapplicationwhereopticalfibrescanbe used.Thefirstworkwaspublishedin1978[13].SOFO,fromthecompanySmartec,isacommercialexamplethatcanbeusedforsurfacemountingorembedding inconcreteandmortars.Itisidealforlong-termstructuraldeformationmonitoringandpresentsa20-yeartrackrecordinfieldapplications.
(a) Faraday effect principle
(b) ABB fibre optic current sensor
Figure1.5 (a)Basicprincipleofopticalfibresensors:thepolarizationoftheinputlightin andopticalfibreisrotatedbytheactionofthemagneticfieldgeneratedaroundaline transmittingcurrent.(b)CommercialABBFOCSsensor.
Inaddition,theinventionofopticalfibreBragggratings(FBGs)in1978[14] widenedevenmorethepossibilitiesofOFSsintermsofdetectionofstrain,because thepathwasopentoincludemultipleBragggratingsinthesameopticalfibre, eachoneoperatingatadifferentwavelength,andtouseamultiplexingtechnology (developedinparallelbackin1980[15]),toanalyseeachsignalseparately.This
FOCS controller
FOCS clamp to a voltage line
canbeusedtomonitorstrainatmultiplepointsinaircrafts,tunnels,etc.,inwhatis typicallycalledstructuralhealthmonitoring[16].ThefirstcommercialBragggratingsensorswereavailablein1995,andsincethatmomentmanycompanieshave commercializedtheirownFBGs.
However,despiteitbeingpossible,unlikeelectronicgauges,toincludemultiple strainOFSsinthesamewireanddespitestrainOFSsbeinglesssensitivetovibrationorheatandfarmorereliablethanelectronicgauges,theyhavenotachieveda commercialsuccesscomparablewiththeOFG.Herewecanseeagoodexampleof theproblemthatfacesOFSs:thereisanelectroniccompetitor,themetallicstrain gauge,thatnowadaysismorewidespreadthanopticalfibregaugesbecauseengineersaremorefamiliarizedwithelectronictechnology.LikeOFSs,electronicsensorshavealsobecomepopularthankstoanothertechnology,electronics,andto thevastutilizationofcopperwireforcommunications.Moreover,thecomputer, thebasicunitintheinformationtechnologyera,isalsobasedonelectronics.All thishasmadeitpossibleforelectronicsensorstonearlymonopolizethedomainof sensors.Therefore,itisnecessarytofindapplicationswhereopticalfibremakesa differencecomparedwiththeelectroniccounterpart.
Inthissense,itisimportanttoconsidertheadvantagesanddisadvantagesof opticalfibre.Themaingoodpointsofopticalfibreare[17,18]:
• Smallsize(itsdiameteristypicallyaround100 μm,whichallowsembeddingin manystructures)andlightweight.
• Lowlosses,whichallowremotesensing.
• Anti-electromagneticinterferenceandanti-radio-frequencyinterference.
• Noelectricalbiasingisrequiredtoguidelight,sotheresultingsensorsarepassive,whichisveryrelevantinenvironmentswithanexplosionrisk.
• Highbandwidth,whichallowsmultiplexingandmulti-parametersensing,
• Distributedsensinginopticalfibrecommunicationlines:itispossibletodevelop modulationtechniquesthatallowphysicalquantitiestobemeasuredalongthe fibreitself.
However,therearealsoimportantconcerns[18],whicharebeingprogressively solvedasthetechnologymatures:
• Cost
• Complexityininterrogationsystems
• Unfamiliarityoftheenduserwiththetechnology
Bytakingalookattheseproperties,itiseasytounderstandwhythemostsuccessfultypeofOFS,intermsofcoveringthesensorsmarket,isdistributedsensing. First,itispossiblewithopticalfibretomakedistributedmeasurementsoverdistancesuptoseveraltensofkilometres,anabilitythatisuniquetofibreoptics. Asecondadvantageofthosementionedaboveisthesmalldiameterofoptical
fibre,whichallowsembeddingitintunnels,bridges,orconcreteconstructions[19, 20],and,onceinstalled,theinitialcostiscompensatedwithacontinuousmonitoringofvariablessuchasstrain,temperature,orvibration,anoperationthatmay lastyearsandthatdoesnotaffecttheopticalfibreitisembeddedin.Thisexplains itssuccessinthefollowingdomains:
• Civilengineering:leakageofdamsandriverembankments,monitoringof cracksinbridgesandotherconcretestructures;structuralhealthmonitoring oflargecivilprojects;andfiremonitoringandsafetyalarmsforroads,subways, tunnels,etc.[21].
• Petrochemical:detectionofoilandnaturalgastransmissionpipelinesorstorage tankleaks;temperaturemonitoringofoildepots,oilpipes,andoiltanks;and detectionoffaultpoints.
• Powercable:detectionandmonitoringofsurfacetemperatureofpowercable andlocationofaccidentpoints;temperaturemonitoringofpowerplantsand substations;anddetectionoffaultpointsandfirealarms.
• Aerospace:monitoringofaircraftpressure,temperature,fuellevel,andlanding gearstatus;temperatureandstrainmonitoringofcompositeskins;andmeasurementofstressandtemperatureofaircraftjetturbineenginesystems[22].
Distributedsensingtechnologycanbeclassifiedintwogroups:quasi-distributed (multiplexingFBGslikeinFigure1.6areagoodexample)anddistributedsensing [24].AcomparisonbetweenbothtechnologiesispresentedinFigure1.7.With quasi-distributedsensing,discretepointscanbemonitored,whereaswithdistributedsensingchangesinanypointintheopticalfibrepathlengthcanbedetected. Effectivegaugelengthsoftheorderof1marecommon,andtherearesomethatgo toevenshorterdiscriminationlengths[8].Regardingpurelydistributedsensing, thefirstworksdatefromthe1980s[25,26],andsincethatmomentuptonow, theutilizationofRayleigh,Brillouin,andRamanscatteringforremotelydetecting changesinaparameterataspecificpointhasbeenwidelyexplored[22,27,28].
Theopticaltime-domainreflectometer(OTDR)isthetypicalcommercialdevice, thoughtherearemanytypesofdetectorssuchastheexamplepresentedin Figure1.7cforsensinganacousticfield.Thebasicprincipleofthistypeofdevice istheinjectionofaseriesofopticalpulsesintothefibreandthefurtherdetection oflightthatisscatteredorreflectedbackfrompointsalongthefibre.Thesepoints maybesplices,failures,orevenchangesintroducedbyvariablessuchastemperature(inthislastcasethesystemcanbeusedtodetectafire),strain,orvibration. Sincethatmomentmanycompanieshavefocusedondistributedsensing,suchas Omnisens,Sensornet,Silixa,Fotec,Luna,OptaSense,orFutureFibreTechnologies,justtomentionafew.
In2017theirmarketwasmorethan1billionUSdollars,anditisexpected togrowata10.4%annualgrowthratethrough2026.Themainapplicationis
(a) Single fibre Bragg grating (FBG) setup
(b) Multiple fibre Bragg grating (FBG) setup
(c) Applications of FBG arrays
Figure1.6 (a)SinglefibreBragggrating.(b)MultiplefibreBragggratingsinamultiplexed systemmonitoredwithaninterrogator.(c)ApplicationsofFBGarraysformonitoringstrainin differentpointsofanaircraftandfordevelopingasmarttextile[23].
theoilandgasverticalsegment,whichoccupieda60.9%shareoftheglobaldistributedfibre-opticsensormarketin2015.Butalsopipelines,intrusiondetection andsecurity,transport,andinfrastructuresareotherimportantdomainswhere thistechnologyisused.
Consequently,itcanbeconcludedthatopticalfibredistributedsensors,along withthegyro,arethetwomostsuccessfulOFSsandbothcasescanserveasan exampletofollowtowardsnewcommercialopportunities.
Inadditiontothis,OFSresearchduringthelastyearshasfocusedontwoimportantfields:thefabricationofspecialtyfibres,wherethemainbreakthrough tookplacein1996withthefirstmicrostructuredopticalfibres[29],andthe
