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Applications of the Fiber Optic Sagnac Interferometer

Session 6. Session 8. Session 7. Session 1. Session 5. Session 4. Session 3. Session 2. Applications of the Fiber Optic Sagnac Interferometer. Blue Road Research. Sagnac Interferometer. Blue Road Research. Session 3, Page 1. Part I Rotation Sensing Part II

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Applications of the Fiber Optic Sagnac Interferometer

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  1. Session 6 Session 8 Session 7 Session 1 Session 5 Session 4 Session 3 Session 2 Applications of the Fiber Optic Sagnac Interferometer Blue Road Research

  2. Sagnac Interferometer Blue Road Research Session 3, Page 1 Part I Rotation Sensing Part II Quasi-Static and Time Varying Sensing

  3. Rotation Sensor Characteristics Blue Road Research Session 3, Page 2 Rate Gyro  = KV  = Rotation rate K = Scale factor V = Output signal

  4. Definition of Terms Blue Road Research Session 3, Page 3 • Rate integration gyro - Integrates angular rate to get angular output • Fixed bias - Output rotation rate with zero input rotation rate • Bias drift - Change in output rate over time (temperature, wear, etc.) • Scale factor - Linearity and hysteresis

  5. Rotation Sensor Performance Factors Blue Road Research Session 3, Page 4 • Sensitivity • Lowest measurable rotation rate • Spectral noise characteristics • Dynamic range • Turn on time

  6. The Sagnac Effect ccw cw cw path: 2R+ RL/c R ccw path: 2R - RL/c Net path difference: 2RL/c  ZR = 2RL/(c) Blue Road Research Session 3, Page 5

  7. The Sagnac Effect ccw cw ZFcw = (Fo+F)(Ln/c) F ZFccw = FoLn/c ZF = FLn/c Setting ZR = ZF Renders F = 2R/n Blue Road Research Session 3, Page 6

  8. Fiber Optic Gyro Competition Blue Road Research Session 3, Page 7 • Mechanical Gyros • Advantages • Established industrial base • Disadvantages • Bearing wear • Start-up time • Reliability

  9. Fiber Optic Gyro Competition Blue Road Research Session 3, Page 8 • Ring Laser Gyros • Advantages • Established industrial base • Replaced mechanical gyros for navigation • Disadvantages • Mechanical dither • Ultraclean vacuum tube technology

  10. Fiber Optic Gyro Tradeoffs Blue Road Research Session 3, Page 9 • All solid state • Packing flexibility • Potentially very long lifetimes • Small size • Low cost

  11. Ring Laser Gyro Assembly Partially transparent mirror Anode Cathode Blue Road Research Session 3, Page 10

  12. Ring Laser Gyro Readout Optics cw beam ccw beam Split detector Rolling fringe pattern Blue Road Research Session 3, Page 11

  13. Ring Laser Lock In Zone Blue Road Research Session 3, Page 12

  14. Open Loop Fiber Optic Gyro Light source Polarizer Modulator Detector Fiber optic loop Blue Road Research Session 3, Page 13

  15. Detection Signals Blue Road Research Session 3, Page 14

  16. Open Loop Fiber Optic Gyro Output Blue Road Research Session 3, Page 15

  17. Closed Loop Fiber Optic Gyro Fiber optic coil Light source Polarizer Modulator Detector Integrator Frequency shifter VCO Oscillator Blue Road Research Session 3, Page 16

  18. Scale Factor Open loop fiber gyro Closed loop fiber gyro  = ZR[c/2RL]  = F(n/2R) Dependence on wavelength Blue Road Research Session 3, Page 17

  19. Correction of Scale Factor -F F Blue Road Research Session 3, Page 18

  20. First Closed Loop Fiber Optic Gyro Blue Road Research Session 3, Page 18A

  21. First Solid State Fiber Optic Gyro Blue Road Research Session 3, Page 18B

  22. 2.5” 1980 Fiber Optic Gyro Blue Road Research Session 3, Page 18C

  23. 1982 Oil Drilling FOG Blue Road Research Session 3, Page 18C

  24. 1983 Closed Loop FOGs Blue Road Research Session 3, Page 18C

  25. First Honeywell Production FOG Blue Road Research Session 3, Page 18C

  26. Litton (NG) FOG IMU Blue Road Research Session 3, Page 18C

  27. The Open Loop Fiber Optic Gyro Marketplace Blue Road Research Session 3, Page 19 • Automobiles and trucks • Pointing and tracking • Robot navigation • Aircraft attitude control • Short range air navigation

  28. The Closed Loop Fiber Optic Gyro Marketplace Blue Road Research Session 3, Page 20 • Medium to long range aircraft • Spacecraft • Missiles • Launch vehicles • Platforms making rapid turns

  29. FOG Manufacturers Blue Road Research Session 3, Page 21 • Hitachi • Closed loop automotive and low cost FOGs • Delivered over supports high end automobiles like Lexus navigators, thousands of units per year • Japan Aviation Electronics • Intermediate grade FOGs for Japan self-defense force, variety of commercial applications, soccer field grass cutters, cleaning robots, mini-crop spraying helicopters…

  30. FOG Manufacturers (continued) Blue Road Research Session 3, Page 22 • Honeywell • Supplies 3 axis FOG navigator for German Dornier commuter aircraft, 777 back up navigator • Leader in commercial aircraft navigation and space based FOG • Northrup • 3 axis closed loop AHRS units with 0.1-1.0 deg/hr performance to full military specifications • Working on full navigation grade 0.01 deg/hr FOGs targets competing with Honeywell on commercial aircraft

  31. FOG Manufacturers (continued) Blue Road Research Session 3, Page 24 • Mitsubishi Precision Company • Flight tested first space based FOG on Feb. 22, 1990 aboard S-520-11 rocket • Makes both open and closed loop FOGs • Photonetics • Closed loop 0.1 deg/hr FOGs to support ship navigation

  32. Estimated FOG Market Size Blue Road Research Session 3, Page 26 • 1995 - $50,000,000 • 2000 - $100,000,000 • 2005 - $150,000,000 • Combination of commercial and military/government funded markets

  33. Fiber Optic Gyro References Blue Road Research Session 3, Page 27 • S. Ezekiel and H.J. Arditty, Editors, “Fiber Optic Rotation Sensors”, Springer-Verlag, New York, 1982. • E. Udd, Editor, “Fiber Optic Gyros: 10th Anniversary Conference”, SPIE Proc., Vol. 719, 1986. • R.B. Smith, Editor, “Selected Papers on Fiber Optic Gyros”, SPIE Milestone Series, Vol. MS 8, 1989.

  34. Fiber Optic Gyro References (continued) Blue Road Research Session 3, Page 28 • S. Ezekiel and E. Udd, “Fiber Optic Gyros: 15th Anniversary Conference”, SPIE Proc., Vol. 1585, 1991. • H. Lefevre, “The Fiber Optic Gyroscope”, Artech House, 1993. • W.K. Burns, Editor, “Optical Rotation Sensing”, Academic Press, 1994.

  35. Part II Blue Road Research Session 3, Page 29 Quasi-Static and Time Varying Sensing Using the Fiber Optic Sagnac Interferometer

  36. Time Varying Environmental Effects-Acoustics Light source Center Detector Acoustic Wave Blue Road Research Session 3, Page 30

  37. Optimized Fiber Coil Configurations Variable coating Shielded Fiber Blue Road Research Session 3, Page 31

  38. Effects of Shielding/Position Induced phase shift unshielded coil Induced phase shift shielded coil Blue Road Research Session 3, Page 32

  39. Time Varying Effects Fiber Coil Length L dy y Response of Fiber G(y,P) Blue Road Research Session 3, Page 33

  40. Example Cases Blue Road Research Session 3, Page 34 I. G(y,P) = A = Constant, R[P(t)] = 0 II. G(y,P) = 0, 0<y<L/2 G(y,P) = A = Constant, L/2<y<L, R[P(t)] = AnL2/4c]dP/dt for P = Bsin(t) R[P(t)] = [ABnL2/4c] sin(t)

  41. Quasi-Static Sensing-Strain Polarizer Light source Fo+F Frequency shifter Detector Fo Blue Road Research Session 3, Page 35

  42. Quasi-Static Sensing Blue Road Research Session 3, Page 36 ZF = F(Ln/c) Suppose ZF = Constant 0 = dF(Ln/c)+FdL(n/c) dF/F = -dL/L

  43. Sagnac Strain Sensor Cabling Light source Detector Frequency shifter Fiber cable Blue Road Research Session 3, Page 37

  44. Earth Movement Detection System Fault line Fiber cables Earth movement Blue Road Research Session 3, Page 38

  45. Monitoring Oil Platform Motion Fiber optic strain sensor Blue Road Research Session 3, Page 39

  46. Stress on Power Lines Fiber strain sensor surrounded by conductive cable elements Blue Road Research Session 3, Page 40

  47. Distributed Sagnac Sensors Blue Road Research Session 3, Page 41 • Changing modes from time varying to quasi-static • Interlaced Sagnac loops • Combination of the Sagnac and Mach-Zehnder interferometers

  48. Changing Mode Distributed Sensor Light source Fo Polarizer Switches Detector Fo+F Frequency shifter Blue Road Research Session 3, Page 42

  49. Interlaced Sagnac Loops Light source, 2 Light source, 1 WDMs I Detector, 1 Detector, 2 Position Blue Road Research Session 3, Page 43

  50. Sagnac/Mach-Zehnder Light source, 1 Sagnac Detector, 1 Mach-Zehnder Detector, 2 Light source, 2 Blue Road Research Session 3, Page 44

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