Fiber Optic Sensors: Fundamentals and Applications

1 Fiber Optic Sensors: Fundamentals and ApplicationsSeptember, 2015 David Krohn, Wave Venture FocusThe major focus of this presentation will be on distributive Fiber Optic sensors which has seen the greatest usageHowever, key Applications for point sensors will be discussedThe market dynamics will be covered briefly Fiber Optic sensor Commercialization Evolution2014 Sensors Telecom1975R&D-Military and IndustrialR&D-Telecommunications1980 Laboratory DevicesMultimode Systems; Mb/s transmission19851stIndustrial Applications and Military SystemsAdvent of Single Mode Systems; Major Infrastructure Build19901stCommercial Gyroscope; Medical ApplicationsEDFA; Undersea Systems; Gb/s transmission19951st Oil & Gas Field Trials and Smart Structures.

2 First FBG Component Advancements and DWDM20001stCommercial Oil & Gas SystemsOptical Networks; Market Peak at $18B; Tb/s transmission2010 Broad commercialization of sensors & instrumentationKey enabling technology for NorthAmerican energy independenceTrials for 100Gb systems. R&D on multi-core fibersAdvantages of Fiber Optic Sensors Nonelectrical Explosion proof Often do not require contact Remotable Small size and light weight Allow access into normally inaccessible areas Potentially easy to install (EMI) Immune to radio frequency interference (RFI) and electromagnetic interference (EMI) Solid state reliability High accuracy Can be interfaced with data communication systems Secure data transmission Resistant to ionizing radiation Can facilitate distributed function in harsh environmentsLightModulationEffectsUsedby FiberSensorstoDetectaPhysicalParameterDI RECT(intrinsic)INDIRECT(extrinsic)

3 HYBRIDF iber itself is thetransducerTransduceracts on the fiberFiber carrieslight in and outof the deviceDIRECT(intrinsic)INDIRECT(extrinsi c)HYBRIDDIRECT(intrinsic)INDIRECT(extrin sic)HYBRIDF iber itself is thetransducerTransduceracts on the fiberFiber carrieslight in and outof the deviceFiber itself is thetransducerTransduceracts on the fiberFiber carrieslight in and outof the deviceClassification of Optical Fiber Sensors by Transducing Approach Classification of Optical Fiber Sensors According to their TopologyFiber Optic Distributed SensorsFiber Optic Distributed SensorsInterferometricBragg GratingRaman (DTS)PhaseTempStrainVibrationTempStrainV ibrationIntensityTempTempStrainBrillouin (DTSS)Multi PointContinuousMulti PointContinuousContinuousRayleigh (DAS)ContinuousFrequencyVibrationAcousti c Pulse Phase Modulated SensorsInterferometersMach Zehnder interferometer configuration Michelson Interferometer configurationInterferometersFabry Perot interferometer configurationSagnac interferometer configuration Phase DetectionChange in length due to mechanical or thermal strain will cause a phase change (Mach-Zehnder interferometer)Provides extremely high resolution Noise issues such as phase noise and multimode noise are addressed in the detection schemes Phase change of a light wave through an optical Fiber of original length that has been stretched by a length ?

4 Intensity versus relative phase shifts dueto constructiveand destructive interference [] + =+ 1102nLnLLL Fabry-Perot Interferometric sensor Concepts Air GapLFiberBragg GratingLReflectionsLLDistributed Interferometric sensor ConfigurationsInterferometric Sensing Performance Long term accuracy -<1% Resolution -< microstrain Position Resolution 1 meter in 10 Km length Can monitor dynamic strain over a broad range of frequencies vibration signature There is a trade-off between distance range and frequency bandwidth (due to time-of-flight limitations).How Does a Fiber Optic Hydrophone Work?Source: Northrop GrummanSolid Mandrel Insensitive toPressure VariationsHollow Mandrel sensitive toPressure VariationsFOS Milestones:Hydrophone DevelopmentInstalled on 62 USS Virginia class nuclear submarinesFO Planar hydrophone Arrays (three flat panels mounted low along either side of the hull), as well as two high frequency active sonars mounted in the sail and keel (under the bow).

5 The result of 15+ years of R&D and $140M of investment!Wavelength Modulated SensorsFiber Bragg GratingsReflectedSignalTransmittedSignal Fiber Bragg Grating SensorBragg Grating Sensorwhere:e = the applied strain,P11, P12 = the stress Optic coefficient,a = the coefficient of thermal expansion,? = Poisson s ratio,= the refractive index of the core, and?= the temperature 1300 nm, a change in temperature of 1 C results in a Bragg wavelength shift (??B) of nm.] = + + + = 21211121(), change in wavelength, associated with both strain and temperature effects, is given by:For constant temperatureThis relationship corresponds to 1 nm of wavelength change for 100 microstrain at a wavelength of 1300 nm. For the case of zero applied Grating sensor ResponseInput SignalReflected SignalBragg GratingStrain Induced Spectral ShiftOptical Fiber Resolution -< microstrain Long term accuracy -<1% Up to 20 sensing points in C band Can monitor low frequency dynamic strain Temperature resolution of 1oC Strain / temperature discrimination is requiredBragg Grating SensorsPerformanceBragg Grating Distributed Sensing System Configurations WDMTDM/WDMHigh Capacity WDM Distributed Sensing System Using Bragg GratingsSource: Micron OpticsBridge Failure in Minneapolis MN Conceptual Use of Static and Dynamic Strain Monitoring in a Bridge ApplicationStrain change with Time Associated with Bridge TrafficSource.

6 Micron OpticsScattering Based SensorsDistributed Sensing ApplicationsDistributed Sensing System Based on ScatteringEmission from Raman, Brillouin and Rayleigh ScatteringRaman Scattering Process in Optical FiberSource: Sumitomo & LIOSR aman Scattering Distributed Temperature Sensing (DTS).Temperature and Strain Sensitivities for Various Scattering Effects in Optical FiberRaman Scattering Performance Only measures temperature and is independent of strain. The temperature resolution is The measurement range is up to 15 km with a 1 meter spatial resolution (up to 25km with a meter resolution) of the location of the temperature perturbation Brillouin Scattering Performance The measurement range of up to 30 km.

7 The sensing point associated with a physical perturbation can be resolved to 1 meter on a 10 km length, but accuracy is reduced as distance increases. The strain resolution is 20 microstrain. However, more advanced detection schemes can have a strain resolution of microstrain. The temperature resolution is While Brillouin scattering is an excellent strain sensor technology, the response time is about 1 second; and therefore, is not suitable for vibration Interferomter Based on Rayleigh Scattering ReferenceReflection 1 Reflection 2 Scanning laserDetectorMach-Zehnder InterferometerDiscrete Fourier TransformOutputReflected IntensityDistance, FrequencyReflection1 Reflection 2 PerformanceAccuracy -2 strainSpatial resolution 1 cmMax.

8 Length -50 meters Distributed Acoustic Sensing (DAS)Based on Rayleigh backscattered light in an optical Fiber (single mode or multi mode)It senses all points along the Fiber and monitors acoustic perturbations to the fiberSpecificationsFrequency range -1mHz to 100kHzSpatial resolution -1 mLength 50 kmStrong applicationsOil and gas seismicPipeline monitoring Oil & Gas ApplicationsFiber Optic Sensors in Oil & GasSource: WeatherfordDTS -SAGDS ource: Petrospec(SAGD) is an enhanced oil recovery technology for producing heavy crude oil utilizing steam injection80% of oil sands require enhanced recovery techniques such as SAGDO ptimizing steam management optimizes reservoir production, reduces costs and limits emissionMonitoring the temperature profile of the steam chamber growth is key to process and efficiency improvements Steam Assisted Gravity DrainageDistributed Fiber Optic temperature sensing systems have provided the monitoring capabilityAdvent of Permanent Ocean Bottom Cable (OBC) Seismic SystemsMajor franchises formedFiber Optics: reach, channel count.

9 ReliabilityEarly growth stageBetween $20-50M cost per field to customerLarge incremental growth potential Optical System Deployment Interpretation Oil Company Sponsors Courtesy Petroleum Geo-ServicesSeismic reservoir management tool to optimize production Source -Qorex Pipeline Distributed Fiber Optic Monitoring SystemSource: SabeusInterferometric and DAS systems can monitor 25 km or longerDTS and DTSS systems have been used to monitor leaks which cause a local temperature drop Fiber Optic interferometric array monitors about 25 Km Multiple arrays cover hundreds of km Data transferred through wireless node In evaluation trials Pipeline Leak Detection(Distributed Brillouin Scattering) Source: OmnisensDAS Acoustic SignaturesSource.

10 OptaSenseMagnetic and Electric Field SensorsFiber Optic Magnetic Field sensor ArchitecturesFaraday Rotating Optic Attached Polarizing OpticsLow Verdet constant in Fiber requires long path length compared with bulk Faraday rotators ensor with Piez CoatingsMagnetostrictive coating can be used for magnetic field sensorsHigh sensitivity potential Biophotonic SensorsBiosensor ConceptIntrinsic Biophotonic SensorsAbsorptionScatteringRaman ScatteringIndex of RefractionFluorescenceEvanescent Wave InteractionPhotonic Bandgap ConfinementFluorescence ArraysFlow CytrometryMechanismsConceptsBiophotonic Interaction Modulated Mach-Zehnder InterferometerEvanescent Wave Fluoroimmunoassay Concept Fiber Optic Enabled Arrays using Fluorescence for High Speed ScreeningFluorescent Array Microsphere Vapor SensorsFigure Fluorescent ArrayMicrosphere Vapor Sensors10 GyroscopesSagnac Effect in a Coiled Fiber Used for Rotation Rate (2LD/c)Noise Sources in an Optical Fiber GyroscopeTypical Precision FOG DesignNorthrop Grumman CommercialInertial Measurement Unit (IMU) with Three Fiber Optic GyroscopesMarketFO sensor Market:Single-Point Sensing20082014 Civil Infrastructure25%Industrial8%Military4%M edical3%Power4%Gyro54%Oil& Gas2%Civil Infrastructure29%Industrial8%Military4%P ower4%Medical3%Gyro50%Oil& Gas2%Total: $194 MillionTotal.