Overview:
Civil structures, including bridges, dams, highways, buildings, pipelines, and power plants, represent investments in the trillions of dollars. Replacement costs for certain individual structures can cost billions. If a structure is damaged or wears out prematurely, the repair costs and costs due to loss of use may be in the millions of dollars. With such great value in these investments and their service, many new efforts are ongoing to apply new technologies to monitor and assess the condition of valuable structures, to increase lifetime and reliability, and, to decrease maintenance activities.
Fiber optic sensor technologies are finding growing application in the area of monitoring of civil structures. In large part due to exceptional advances in fiber telecommunications technologies, the costs for fiber sensors has been dropping steadily, and this trend will continue. Further, measurement capabilities and system configurations (such as wavelength multiplexed, quasidistributed sensor arrays) that are not feasible with conventional technologies, now are possible with fiber sensors, enabling previously unobtainable information on structures to be acquired.
This report provides a detailed overview of fiber sensor technologies and assesses the potential markets for fiber optic sensors in civil structures. Opportunities and strategies are presented.
Table Of Contents
Executive Summary
1.0 Introduction
2.0 Advantages of Optical Fiber Sensors
- Weight and Size Benefits
- EMI/RFI Benefits
- Optical Multiplexing and Inherent Bandwidth Benefits
- Improved Environmental resistance in many applications
- Scale flexibility for small-gage (mm) to long gage (Km) measurement
- Geometric flexibility for gradient sensing and signal gain
3.0 Photonics Concepts, Optical Fiber, Components, and Instrumentation
- Photons, Rays, And Waves
- Optical Fiber Design And Characteristics
- Components and Devices
- Key Parameters of Light and Light Sources
- Optical Detectors and Measurement Instrumentation
- References for section 3
4.0 Fiber Transducers and Sensors For Civil Structures
- Optical Fiber as a Transducer
- Intensity Based Transducers
- Grating Fiber Transducers
- Interferometric Sensors
- References for section 4
5.0 Distributed and Multiplexed Fiber Sensor Systems
- Quasi-Distributed / Multiplexed Systems
- Fully Distributed Systems
- Integrating Systems With Antenna Gain
- Comparison of Distributed Systems
- References for section 5
6.0 Status of Fiber Optic Sensors and Systems
- Status of Fiber Sensor Systems
- Numbers of Fiber Sensor Companies
- Impact of Telecommunications Industry on Fiber Sensors / Systems
7.0 Motivation for Health Monitoring of Civil
- Description of Civil Structures
- Life Cycle of (a) Civil Structure
- Value Maintenance of Structure
- Discussion Of Conditions And Problems
- References for section 7
8.0 Examples Of Fiber Sensor Technologies In Civil Structure Applications
- Highways and Bridges
- Piers And Docks
- Summary of Additional Examples
- Pros And Cons Of Pilot Projects' Assessments
- References for section 8
9.0 Numbers Of Structures For Which Potential Benefits Exist
- Highway Bridges
- Hiighways - Weigh-In-Motion
- Railroad Bridges
- Pipeline
- Commercial Buildings
- Piers and Docks
- Summary of Key Structure's Data
- References for section 9
10.0 Market Potential
- Highway Bridges
- Railroad Bridges
- Buildings
- Pipelines
- Piers and Docks
- Total Projections
- Comments regarding non-civil-structure opportunities
- References for section 10
11.0 Summary
12.0 Conclusion
13.0 Market Strategies and Opportunities
- Strategies for Developers of Fiber Sensors and Systems
- Opportunities in Fiber Sensor Technologies
14.0 Appendix 1: Web Links
List of Figures
- 3.1 Electromagnetic Spectrum
- 3.2 Rays of Light Indicating Direction of Light Motion
- 3.3 Light Wave with Electromagnetic Field Perpendicular to Direction of Light Travel
- 3.4 Light Refraction at Interface of Two Materials
- 3.5 Total Internal Reflection
- 3.6 Total Internal Reflection for Glass to Air Interface
- 3.7 Fiber Core and Cladding
- 3.8 Plot of Index of Refraction for Core and Cladding
- 3.9 Numerical Aperture
- 3.10 Fiber Modes
- 3.11 Overfilled Numerical Aperture Wastes Light
- 3.12 Graded Index Fiber Profile
- 3.13 Graded Index Fiber
- 3.14 Spectral Attenuation Profile for Conventional Silicon Glass Fiber
- 3.15 Fusion Splice
- 3.16 Mechanical Splices
- 3.17 Example of Basic Coupler Function
- 3.18 Switch for Sensors
- 3.19 Basic WDM
- 3.20 External Amplitude Modulator
- 3.21 Optical Isolator
- 3.22 Power and Energy for a Square Pulse
- 3.23 Source Spectrum and Lindwidth
- 3.24 Source Brightness and Radiance
- 3.25 Spectrum Emission / Light Emitting Diodes (LED's)
- 3.26 LED Spectrum
- 3.27 Spontaneous Emission of Atom and Energy Level Illustration
- 3.28 Stimulated Emission of Excited Atom
- 3.29 Stimulated Emission of Population of Excited Atoms
- 3.30 Fundamental Requirements for Laser
- 3.31 Fiber Laser
- 3.32 Generation of Photocurrent
- 3.33 Absolute Responsivity of Various Light Detectors (courtesy International Light)
- 3.34 Insertion Loss Measurement
- 3.35 Example of Conventional OTDR Display
- 4-1 Closure / Vibration Sensors Based on Numerical Aperture
- 4-2 Numerical Aperture Fiber Sensor Based on a Flexible Mirror
- 4-3 Fiber Optic Translation Sensor Based on Numerical Aperture
- 4-4 Fiber Optic Rotary position Sensor Based on Reflectance
- 4-5 Linear Position Sensor Using Wavelength Division Multiplexing
- 4-6 Linear Position Sensor Using Time Division Multiplexing
- 4-7 Pressure / Index of Refraction Measurement using Critical Angle Properties of a Fiber
- 4-8 Liquid Level Sensor Based on Total Internal Reflection
- 4.9 Evanescence Based Fiber Optic Sensor
- 4-10 Microbend Fiber Sensor
- 4-11 Grating Based Vibration / Acceleration Intensity Sensor
- 4-15 Single Grating Written onto Ordinary Single Mode Fiber to Form Single Axis Strain or Temperature Sensor
- 4-16 Shifts in Spectral Peaks Reflected from Fiber Grating Sensor due to Axial Strain or Temperature Changes
- 4-17 Dual Overlaid Gratings Written onto Polarization Preserving Fiber
- 4-18 Spectral Shifts of Peaks due to Axial and Transverse Strain on a Multi-Axis Fiber Grating Sensor
- 4-19a Sample Data of the Multi-Axis Sensor's Response to Axial Strain
- 4-19b Sample Data of the Multi-Axis Sensor's Response to Transverse Strain
- 4-20 Etalon-Based Demodulators
- 4-21 Schematic of a Fiber Grating Demodulation System Employing a Chirped Fiber Grating Spectral Fiber
- 4-22 Load Cell with Embedded Distribution Transverse Strain Sensing Fiber Grating Sensors
- 4-23 Fiber Grating Based Load Cells Monitoring Decks and Counterweights in Drawbridge Applications
- 4-24 Monitoring of Bridge Scouring and Load Distributions using Fiber Grating Based Load Cells
- 4-25a Intrinsic Interferometric Sensor Types
- 4-25b Example of Extrinsic Interferometric Sensor
- 4-26 Smartec Sofo Unit
- 4-27 Optical Paths in FFPI to Form Interferometer
- 4-28 Intrinsic Fiber Fabry-Perot Etalon Sensors used for Strain Measurements in Cylinder Heads of Combustion Engines
- 4-30 Faraday Mirror (OFR)
- 4-31 Triple Element Receiver
- 5-1 Array of Individual Sensor Systems
- 5-2 TDM Multiplexing Techniques
- 5-3 Maximum Power Returned / Sensor for 3 TDM Systems
- 5-4 Subcarrier Chirped RF FDM System
- 5-5 Quasi-Distributed polarimetric Strain Sensing System
- 5-6 WDM System for Transmissive Intensity Sensors
- 5-7 In-Line Bragg Grating Sensing System
- 5-8 Hybrid Time and Wavelength Division Multiplexed System
- 5-9 Enhanced Brillouin Scattering Distributed Sensor
- 5-10 Sagnac-Mach-Zehnder Distributed Sensor
- 5-11 Sagnac-Michelson Distributed Sensor
- 6-1 Summary Table of Companies with Fiber Optic Sensors
- 7-1 General Lifetime Profile for Civil Structure
- 7-2 Accelerated Deterioration in Structure Performance
- 7-3 Potential Improvement in Structure Performance due to Maintenance
- 7-4 Ideal Cost Profile for Structure Maintenance and Repair
- 7-5 Performance Improvement from Monitoring and Reliability Modeling
- 7.6 Cost Benefits from Monitoring and Reliability Modeling
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