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An Introduction to Fiber Optic Sensors

An Introduction to Fiber Optic Sensors

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An Introduction to Fiber Optic Sensors

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  1. An Introduction to Fiber Optic Sensors Eric Udd Blue Road Research 376 NE 219th Avenue Gresham, Oregon 97030 503-667-7772 (F) 503-667-7880 www.blueroadresearch.com

  2. Outline • Session 1 -Fundamental Components and Concepts • Session 2 -Intensity Based and Fabry-Perot Interferometric Sensors • Session 3 -Applications of the Fiber Optic Sagnac Interferometer • Session 4 -The Mach-Zehnder and Michelson Interferometers and Multiplexing • Session 5 -Fiber Optic Smart Structures for Natural, Civil, and Aerospace Applications • Session 6 - Fiber Optic Grating Sensors and Applications

  3. Session 6 Session 8 Session 7 Session 1 Session 5 Session 4 Session 3 Session 2 Fundamental Components and Concepts Blue Road Research

  4. Fundamental Components and Concepts Blue Road Research Session 1, Page 1 • Sensor capabilities • Advantages • Historical trends • Sensor types • Fundamental components • Fiber fabrication / coupling • Light sources • Modulators • Detectors

  5. Fiber Optic Sensor Capabilities Blue Road Research Session 1, Page 2 • Rotation, acceleration • Electric and magnetic fields • Temperature and pressure • Acoustics and vibration • Strain, humidity, and viscosity

  6. Fiber Optic Sensor Advantages Blue Road Research Session 1, Page 3 • Lightweight / nonobtrusive • Passive / low power • EMI resistant • High sensitivity and bandwidth • Environmental ruggedness • Complementary to telecom / optoelectronics

  7. Fiber Optic Sensors Historical Trends 1980 1990 2000 Blue Road Research Session 1, Page 4 Few, high-priced components, laser diodes, microoptics Low-cost basic components, laser diodes pigtailed, fiber beamsplitters Low-cost complex components, mass produced integrated optics

  8. Fiber Optic Sensors Historical Trends 1980 1990 2000 Blue Road Research Session 1, Page 5 Niche markets - RF temperature Mass markets emerge - fiber gyros, medical, lab instruments, manufacturing Fiber optic systems - fiber optic smart structures, industrial systems

  9. Fiber Optic Sensors What’s Next? 2005 2010 2015 Blue Road Research Session 1, Page 5A Fiber optic health and structural monitoring systems on about 100 bridges, aerospace SHM technology moves toward level 6 Hundreds of civil structure installations, aerospace fiber optic SHM moves to level 8 and 9 with initial deployments Fiber optic SHM systems are mandated on new civil and aerospace structures

  10. Fiber Optic Sensors What’s Next? 2005 2010 2015 Blue Road Research Session 1, Page 5B Oil and gas deployments start to appear Hundreds of oil and gas wells uses downhole fiber optic sensor systems, platforms begin to use fiber optic SHM systems Thousands of systems are deployed for many high value oil and gas wells, fiber optic SHM mandated on some oil platforms

  11. Extrinsic Fiber Optic Sensors Light modulator Input fiber Output fiber Environmental signal Blue Road Research Session 1, Page 6

  12. Intrinsic Fiber Optic Sensors Optical fiber Environmental signal Blue Road Research Session 1, Page 7

  13. Fundamental Components Blue Road Research Session 1, Page 8 • Optical fiber • Light sources • Beam conditioning optics • Modulators • Detectors

  14. Total Internal Reflection Air Water Bottom of pool Blue Road Research Session 1, Page 9

  15. Optical Fiber Structure Numerical aperture n (clad) n (core) Waveguide axis Blue Road Research Session 1, Page 10

  16. Types of Optical Fiber Blue Road Research Session 1, Page 11 • Multimode step index • Graded index multimode • Single mode • Polarization preserving • Polarizing

  17. Types of Polarization Preserving Fiber Blue Road Research Session 1, Page 12 Elliptical clad Soft glass side pit Stress rod

  18. Fiber Depolarizer Broadband input light beam Polarization preserving fiber sections at 45 degrees Blue Road Research Session 1, Page 13

  19. Fiber Fabrication Types Blue Road Research Session 1, Page 14 • Modified chemical vapor deposition • Outside chemical vapor deposition • Vapor axial deposition • Rods in glass tube

  20. Fiber Coupling Techniques Blue Road Research Session 1, Page 15 • Fused biconical taper • Polished • Etched • Microoptic • Integrated optic

  21. Fiber Coupling Techniques clad core Blue Road Research Session 1, Page 16

  22. Light Sources Blue Road Research Session 1, Page 17 • Light emitting diodes • Laser diodes • Superradiant diodes • Fiber Lasers

  23. Spontaneous Emission Blue Road Research Session 1, Page 18 • Low probability of photon interaction • Wide spectral bandwidth • High immunity to low level backscatter

  24. Stimulated Emission Blue Road Research Session 1, Page 19 • High probability of photon interaction • Narrow bandwidth due to spectral selectivity of cavity • High sensitivity to low level backscatter

  25. Superradiance Blue Road Research Session 1, Page 20 • High probability of photon interaction • Wide bandwidth due to spectrally nonselective cavity • Moderate sensitivity to backscatter

  26. Surface Emitting LED - - N AlyGa1-yAs P GaAs Metal electrodes P AlxGa1-xAs + Blue Road Research Session 1, Page 21

  27. Laser Diode and Edge Emitting LED Structures Metal electrode Insulator GaAs substrate Light emitting area Metal electrode Blue Road Research Session 1, Page 22

  28. Characteristic Current/Power Curves Blue Road Research Session 1, Page 23

  29. Fiber Lasers Pump laser diode WDM coupler Active fiber Blue Road Research Session 1, Page 24

  30. Fiber Optic Modulators Blue Road Research Session 1, Page 25 • Electrooptical • Acoustooptical • Magnetooptical • Mechanical

  31. Electrooptic Modulator Electrode Fiber Integrated optic waveguide Blue Road Research Session 1, Page 26

  32. Acoustooptic Modulator hf h(f+F) / hF Blue Road Research Session 1, Page 27

  33. Mechanical Modulators Expansion Blue Road Research Session 1, Page 28 Constriction

  34. Detectors Blue Road Research Session 1, Page 29 • PIN photodiodes • Avalanche photodiodes • Spectrally selective detectors

  35. Summary - Basic Elements of a Fiber Optic Sensor Beam conditioning optics Modulator Light source Transducer Detector Blue Road Research Session 1, Page 30

  36. Session 6 Session 8 Session 7 Session 1 Session 5 Session 4 Session 3 Session 2 Intensity Based and Fabry-Perot Interferometric Sensors Blue Road Research

  37. Closure and Vibration Sensors Based on Numerical Aperture d Blue Road Research Session 2, Page 1

  38. Closure and Vibration Sensors Based on Numerical Aperture Flexible mounted mirror Blue Road Research Session 2, Page 2

  39. Translation Sensor Based on Numerical Aperture Detectors Input light Collection fibers Blue Road Research Session 2, Page 3

  40. Rotary Position Based on Reflectance Variable reflectance shaft Input/output fibers Blue Road Research Session 2, Page 4

  41. Linear Position Sensors Wavelength Division Encoder card 1 2 3 WDMs Light source Detectors 1 2 3 Blue Road Research Session 2, Page 5

  42. Linear Position SensorsTime Division Encoder card Light source Time delay loop Detector Blue Road Research Session 2, Page 6

  43. Critical Angle Pressure/Index of Refraction Measurement Fiber core no outside medium index of refraction Mirror Light input, output Fiber cladding Blue Road Research Session 2, Page 7

  44. Liquid Level Sensor Based on Total Internal Reflection Liquid Blue Road Research Session 2, Page 8

  45. Evanescence Based Sensors Interaction length L Light in d Light outputs Fiber cores Blue Road Research Session 2, Page 9

  46. Microbend Fiber Sensors Light source Microbend transducer Detector Blue Road Research Session 2, Page 10

  47. Grating Based Intensity Sensor Stationary mount Graded index lens Output fiber Input fiber Spring Blue Road Research Session 2, Page 11

  48. Dynamic Range Limit Output Intensity Position of Grating Blue Road Research Session 2, Page 12

  49. Dual Grating Mask, 90 Degrees Out of Phase Region 1 Region 2 Blue Road Research Session 2, Page 13

  50. Quadrature Detection 2 1 2 1 Blue Road Research Session 2, Page 14