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Prepared by: Andrew Moss Dept. of Electrical and Computer Engineering Utah State University

ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: Optical Fiber Sensors. Prepared by: Andrew Moss Dept. of Electrical and Computer Engineering Utah State University. 2/16/2008. Outline. Reference list Overview Major applications

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Prepared by: Andrew Moss Dept. of Electrical and Computer Engineering Utah State University

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  1. ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: Optical Fiber Sensors Prepared by: Andrew Moss Dept. of Electrical and Computer Engineering Utah State University 2/16/2008

  2. Outline • Reference list • Overview • Major applications • Basic working principle illustrated • Major specifications • Limitations ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  3. Reference list • 1. E. Udd, Editor, ‘Fiber Optic Sensors: An Introduction for Engineers and Scientists’,Wiley, New York, 1991. • Blue Road Research, ‘Overview of Fiber Optic Sensors’, www.bluerr.com/papers/Overview_of_FOS2.pdf • K.T.V Grattan and B.T. Meggit, ‘Optical Fiber Sensor Technology, Advanced Applications – Bragg Gratings and Distributed Sensors’ Kluwer Academic Publishers, 2000 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  4. To explore further (survival pointers of web references etc) • http://www.bluerr.com/ • Blue Road Research, good information in the Applications and Publications section. • http://www.boulder.nist.gov/div815/81503_pubs/ofs.htm • NIST list of publications • http://en.wikipedia.org/wiki/Optical_fiber#Fiber_optic_sensors • Very basic definitions and information ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  5. Overview • Light in optical fibers can be modulated by amplitude, frequency, phase or polarization to carry signals. • Two major types of fiber optic sensor: • Extrinsic or Hybrid • Intrinsic or All Fiber ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  6. Overview - Extrinsic • Optical fibers carry the signal but modulation is done by an exterior component. Diagram from: Fiber Optic Sensor Workbook, Eric Udd ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  7. Overview - Intrinsic • Modulation is done directly by the environmental parameter to be measured. Diagram from: Fiber Optic Sensor Workbook, Eric Udd ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  8. Major Applications • Measure: • Rotation • Accleration • Electric and magnetic field strengths • Temperature • Acoustics • Pressure • Vibrations • Linear and angular position • Strain • Viscosity • Humidity • Chemical measurements • And more… ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  9. Major Advantages • Small • Lightweight • Passive • Low power • Wide bandwidth • Rugged • Resistant to EM interference • High sensitivity ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  10. Major Advantages • Multiplexing • Optical fiber sensors can be multiplexed in a variety of ways allowing multiple sensors to be attached to a single fiber. This allows for large, distributed sensor networks. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  11. Principle – Simple Extrinsic The amount of light transmitted from fiber 1 to fiber 2 depends on the distance, d, between the fiber ends. This can be controlled by an actuator, temperature change, a force, pressure or vibrations. Diagram from: Fiber Optic Sensor Workbook, Eric Udd ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  12. Principle – Angular Position Diagram from: Fiber Optic Sensor Workbook, Eric Udd Reflectors are placed in patterns on the rotational shaft. These patterns form a gray code which is read by a series of optical fibers that detect the presence or absence of a reflector. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  13. Principle – Intrinsic #1 An optical fiber ends with a right angle as shown which reflects all of the light back through total internal reflection. When the probe is placed in a medium other than the reference, the index of refraction changes and some of the light escapes the probe, decreasing the amplitude. Diagram from: Fiber Optic Sensor Workbook, Eric Udd ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  14. Principle – Intrinsic #2 Two simple optical fibers are placed in close proximity. Some of the light leaks from one to the other, ie cross coupling occurs. The amount of evanescence caused depends on several factors which can be sensed through the measured coupling. Diagram from: Fiber Optic Sensor Workbook, Eric Udd ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  15. Principle – Spectrally Based Diagram from: Fiber Optic Sensor Workbook, Eric Udd When the blackbody’s temperature increases it begins to glow, acting as a light source. This is transmitted to detectors where the blackbody is measured and used to determine the temperature. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  16. Principle – Interferometer Based Fiber optic gyroscope. Light is injected into a fiber coil from both directions. The phase difference of the two signals is then detected. If the coil is stationary the phase difference is 0, but if it is rotating the phase difference is proportional to the rotation rate. Diagram from: Fiber Optic Sensor Workbook, Eric Udd ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  17. Major Specifications • Dynamic range • Accuracy • Designed measurement parameters • Response time • External sensors required (if any) • Operating wavelengths ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  18. Limitations • Generally have to be tuned to a specific wavelength to function properly. • This can be used to limit noise susceptibility but limits the general application of any given sensor. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  19. Limitations • Multiple potential error sources (connectors, splices, microbending, misalignment, etc) • May be circumvented by using two wavelengths in the sensor, one of which is used to calibrate out the noise. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  20. Other Considerations • Research area • Optical fiber sensors are relatively new for most applications because the cost of lasers and optical fibers has only recently become practical for most things. This means that new research is still being conducted to find new ways to apply optical sensors. It is a changing area at this time. • Robustness • The robustness of optical fibers makes them usable in many conditions(high temperature, EM interference, etc) which exclude other sensors. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  21. Other Considerations • Optical fiber sensors can be found at most major suppliers of electronic sensors. They are not classified specifically as optical fibers sensor but rather by the parameter they are designed to sense. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

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