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Intensity Modulated Fiber Optic Sensors Pdf 11

With the addition of two authors who bring 75 years of combined experience in fiber optic sensor technology, this edition is a significant update and an excellent resource for any engineer who has an interest in advanced sensing systems.

Intensity Modulated Fiber Optic Sensors Pdf 11

Introduction 1 Fiber Optic Fundamentals 1.1 Refraction and Total Internal Reflection1.2 Meridional Rays1.3 Skew Rays1.4 Bent Fibers1.5 Mechanisms of Attenuation1.6 Waveguide Propagation1.7 Evanescent Wave1.8 Cross Coupling1.9 Scattering1.10 Mode Patterns1.11 Fiber Types1.12 Polarization-Maintaining Fibers 2 Fiber Optic Sensor Fundamentals2.1 Background2.2 Sensor Categories2.3 Distributed Fiber Optic Systems 3 Intensity-Modulated Sensor3.1 Introduction3.2 Transmissive Concept3.3 Reflective Concept3.4 Microbending Concept3.5 Intrinsic Concept3.6 Transmission and Reflection with Other Optical Effects3.7 Speckle Pattern3.8 Sources of Error and Compensation Schemes 4 Phase-Modulated Sensors 4.1 Introduction4.2 Interferometers 4.2.1 Mach-Zehnder 4.2.2 Michelson 4.2.3 Fabry-Perot 4.2.4 Sagnac4.3 Phase Detection4.4 Detection Schemes4.5 Practical Considerations 5 Wavelength-Modulated Sensors 5.1 Introduction5.2 Bragg Grating Concept5.3 Bragg Grating Sensors5.4 Distributed Sensing5.5 Wavelength Detection Schemes5.7 Harsh Environments 6 Scattering-Based Sensors 6.1 Absorption and Transmission Loss in Optical Fibers6.2 Optical Time-Domain Reflectometry (OTDR)6.3 Light-Scattering Mechanisms 6.3.1 Elastic versus inelastic scattering 6.3.2 Stokes and anti-Stokes scattering components 6.3.3 Scattering emission spectrum6.4 Rayleigh Scattering6.5 Raman Scattering6.6 Brillouin Scattering 6.6.1 Stimulated Brillouin scattering6.7 Distributed Fiber Sensing and Scattering Effects 7 Polarization Based Sensors 7.1 Introduction7.2 Analysis of Birefringent Optical Systems7.3 Birefringent Effects in Bragg Gratings 8 Digital Switches and Counters 8.1 Introduction8.2 Scan Modes8.3 Excess Gain8.4 Contrast8.5 Beam Diameter8.6 Electro-Optic Interface8.7 Applications 9 Displacement Sensors 9.1 Introduction9.2 Reflective Technology9.3 Microbending Technology9.4 Modulating Technology9.5 Fabry-Perot Technology9.6 Bragg Grating Technologies9.7 Applications 10 Strain Sensors 10.1 Strain Sensors10.2 Interferometric Strain Sensors10.3 Applications 11 Temperature Sensors 11.1 Introduction11.2 Reflectance and Absorbance Sensors11.3 Fluorescence Sensors11.4 Microbending Sensors11.5 Black-body Radiation11.7 Interferometric Sensors11.8 Fiber Bragg Grating Sensors11.9 Distributed Temperature Sensing (DTS)11.10 Applications 12 Pressure Sensors 12.1 Introduction12.2 Conventional and Specialized12.3 FBG-based Optical Sensors12.4 Fabry-Perot-based Optical Sensors12.5 Packaging12.6 Field Installation 13 Flow Sensors 13.1 Introduction13.2 Turbine Flowmeters13.3 Cantilevered-Beam Flow Sensors13.4 Differential-Pressure Flow Sensor13.5 Vortex-Shedding Flow Sensor13.6 Laser Doppler Velocity Sensors13.7 Indirect Flow Monitoring13.8 Applications 14 Magnetic and Electric Field Sensors 14.1 Introduction14.2 Magnetic Field 14.2.1 Faraday Rotation-based Sensors 14.2.2 Phase modulation14.3 Electric Field 14.3.1 Polarization Modulation 14.3.2 Phase modulation 15 Chemical Analysis 15.1 Introduction15.2 Fluorescence15.3 Absorption15.4 Scattering15.5 Refractive Index Change 15.6 Color Changes15.7 Interferometry15.8 Distributed Fiber Optic Chemical Sensors15.9 Fiber-Optics-Enabled Spectroscopy15.10 Applications 16 Biophotonic Sensors 16.1 Introduction16.2 Intrinsic Biophotonic Sensors 16.2.1 Intrinsic biophotonic sensors: evanescent wave interaction 16.2.2 Intrinsic biophotonic sensors: using photonic crystal fibers 16.2.3 Intrinsic biophotonic sensors: fluorescent microsphere array sensors 16.2.4 Intrinsic biophotonic sensors: distributed sensor concepts 16.2.5 Intrinsic biophotonic sensors: surface plasmon resonance16.3 Extrinsic Biophotonic Sensors 17 Rotation Rate Sensors17.1 Introduction17.2 Sensor Mechanism17.3 Reciprocity17.4 Noise Limitations17.5 Resonators17.6 Comparison of Resonator (RFOG) and Interferometer (IFOG) Gyroscopes 18 Distributed Sensing Systems 18.1 Introduction18.2 Applications18.3 Distributed Temperature Sensing Applications in the Oil and Gas Industry 19 Market Opportunities 19.1 Introduction19.2 Barriers to Market Growth19.3 Summary and Conclusions

In early industrial applications, single point fiber optic sensors were used as an alarm to indicate the absence or presence of an object. As the technology evolved, the functionality increased to accurately determine the position of an object. Many of the sensing concepts that will be discussed throughout this book will be for single point sensors which operate by detecting changes in the intensity of light (see Chapters 3, 8, and 9). They operate by altering the transmitted or reflected light intensity in a manner proportional to the parameter being sensed such as temperature, strain, or displacement (position). The sensing functionality can be expanded to monitor electric and magnetic field measurements using polarization concepts. As an example, certain materials exhibit Faraday rotation, which alters the plane of polarization and the resulting transmitted light intensity in the presence of a magnetic field. Polarization-based sensors are discussed in Chapter 7.

Interferometric sensors compare the phase of light in a sensing fiber to a reference fiber. Small phase shifts can be detected with extreme accuracy. The phase shifts are generated by changes in strain and/or temperature in the sensing fiber. This family of sensors has been especially useful in monitoring dynamic strain (vibration) (see Chapter 4). Also, a Sagnac interferometer is an interferometric sensor configured to be sensitive to rotation (Chapter 17). Two examples of successful commercialization of interfermetric-based sensors are hydrophones for submarine detection and fiber optic gyroscopes for advanced navigation systems. Both are for military applications primarily and have performed well for over 30 years with thousands of systems deployed.

A wavelength or spectral shift is another sensing approach. By introducing coatings on the fiber or a target that fluoresces, under certain conditions (usually related to chemical interaction or temperature fluctuation), a chemical reagent can be detected or temperature can be monitored. A more widely used spectral shift approach uses Bragg gratings, which are reviewed in detail in Chapter 5. A Bragg grating is characterized by having a resonant wavelength that is reflected as light is transmitted through the grating. The reflected light is very sensitive to the grating spacing and the index of refraction of the grating material. Temperature and strain alter both of these parameters. As a result, Bragg gratings can function as temperature or strain sensors. While Bragg gratings have been used as single point sensors, they have had great utility as quasi-distributed sensors in which multiple sensors are located along a single fiber.

Light-scattering phenomena have emerged in the last 10 years to be a key family of technologies to enable fully distributed fiber optic sensing systems. Distributed sensing systems allow any point along a fiber to function as a sensor, with virtually thousands of sensing points along a single fiber that may exceed 30 km in length. The basic sensing mechanisms are Raman scattering, Rayleigh scattering, and Brilloiun scattering. Detailed descriptions of how these sensors work are given in Chapters 6 and 18. Briefly, Raman scattering is sensitive to temperature but not strain, and makes an excellent distributed temperature sensor referred to as DTS. Brillioun scattering is sensitive to temperature and strain and is the basis for distributed temperature and strain sensors referred to as DTSS. Rayleigh scattering is sensitive to acoustic vibrations and is used a distributed acoustic sensor referred to as DAS. DTS and DAS approaches have been especially effective for oil and gas applications.

A very important point that is understated is that fiber optic sensing systems have enabled smart oil and gas wells that are allowing North America to gain energy independence. Fiber optic sensor technology has a long history of development and commercialization successes. The technology has not yet reached maturity and will likely expand and create many new applications and commercialization opportunities.


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