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Retro-Reflective_Fiber_Optic_Displacement_Sensor.pptx

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Retro-Reflective_Fiber_Optic_Displacement_Sensor.pptx

  1. 1. Bhoj Reddy Engineering College For Women Department of Electronics and Communications Engineering (Sponsored by Sangam Laxmibai Vidyapeet, approved by AICTE & affiliated to JNTUH) Seminar Incharge: Internal Guide: Presented By: G.Srilakshmi Saba Sultana Y.Bhargavi(20325A0401) Assistant Professor(ECE) Associate Professor(ECE) lV ECE A Retro-Reflective Fiber Optic Displacement Sensor
  2. 2. Contents • Introduction • Fiber optics • Construction of Fiber optics • Total internal reflection • Block diagram of FODS • Working • Influence of manufacturing tolerances on performance • Various factors and its impact • Advantages • Applications • Conclusion • References 2 Retro-Reflective Fiber Optics Displacement Sensor
  3. 3. Introduction 3 • Fiber optic displacement sensors will play an increasingly larger role in a broad range of industrial, military and medical applications. • Multimode plastic fibers are in a great demand for the transmission and processing of optical signals in optical fiber communication system. • They are also widely used in sensing applications because of their better signal coupling, large core radius, and high numerical aperture as well as able to receive the maximum reflected light from the target. • The measurement of displacements is based on the intensity modulation technique. Retro-Reflective Fiber Optics Displacement Sensor
  4. 4. …..Continuation • The sensor performance and accuracy of measurement strongly depend on the geometrical parameters of the probe. • Taguchi method is used for robust parameter design of retro reflective fiber optic displacement sensor. 4 Retro-Reflective Fiber Optics Displacement Sensor Fig-1.Retro-reflective fiber optics displacement sensor
  5. 5. Fiber Optics • An optical fiber is a glass or plastic fiber that carries light along its length. • Specially designed fibers are used for a variety of other applications, including sensors and fiber lasers • Light Travels through the core by total internal reflection • Fiber optics materials: i. Glass ii. Plastic iii. Both of them 5 Retro-Reflective Fiber Optics Displacement Sensor
  6. 6. Construction of Fiber Optics A fiber optic cable consists of five main components: • Core • Cladding • Coating • Strength Member • Cable jacket. 6 Retro-Reflective Fiber Optics Displacement Sensor Fig-2.Construction of Fiber optics
  7. 7. …..Continuation • Core: This is the physical medium that transports optical signals from an attached light source to a receiving device.It is protected by the cladding. The diameter of the core depends upon the application used. • Cladding:This is the thin layer that surrounds the fiber core and serves as a boundary that contains the light waves and causes the refraction, enabling data to travel throughout the length of the fiber segment. • Coating:This is a layer of plastic that surrounds the core and cladding to reinforce and protect the fiber core. Coatings are measured in microns and can range from 250 to 900 microns. 7 Retro-Reflective Fiber Optics Displacement Sensor
  8. 8. …..Continuation • Strength member: These components help protect the core against crushing forces and excessive tension during installation. • Cable jacket : This is the outer layer of any cable. Most fiber optic cables have an orange jacket, although some types can have black or yellow jackets. 8 Retro-Reflective Fiber Optics Displacement Sensor Fig-3. Fiber Cable
  9. 9. Total Internal Reflection 9 Retro-Reflective Fiber Optics Displacement Sensor Fig-4.Total internal reflection in fiber optics
  10. 10. …..Continuation • Definition : The phenomenon which occurs when the light rays travel from a more optically denser medium to a less optically denser medium. • Following are the two conditions of total internal reflection: 1. The light ray moves from a more dense medium to a less dense medium. 2. The angle of incidence must be greater than the critical angle. • When light travels from one medium to another it changes speed and is refracted. If the light rays are travelling for a less dense material to a dense medium they are refracted towards the normal and if they are travelling from a dense to less dense medium they are refracted away from the normal. 10 Retro-Reflective Fiber Optics Displacement Sensor
  11. 11. Block diagram of FODS 11 • It consists of a light source, a fiber optic probe and a silicon detector, which is connected to a lock-in amplifier and computer. • The fiber probe is a bundled plastic fiber, which consists of one transmitting core and one or more receiving cores. • The light source is a He-Ne laser with a peak wavelength of 633nm, which is modulated externally by chopper with a frequency of 200Hz. • The modulated light source is used in conjunction with lock-in amplifier to reduce the dc drift and interference of ambient stray light. Retro-Reflective Fiber Optics Displacement Sensor
  12. 12. ……Continuation 12 Retro-Reflective Fiber Optics Displacement Sensor Fig-5.Block diagram of FODS
  13. 13. Working of FODS • The light from a light source enters a transmitting core and then radiates to the target. • The light reflected from object surface is transmitted through the receiving core to a photo-detector. • The amount of light returning to detector depends on the displacement between the end of the probe and the target being monitored. • For the displacement a flexible adjusting mechanism using piezoelectric is required. 13 Retro-Reflective Fiber Optics Displacement Sensor
  14. 14. Influence of Manufacturing Tolerances on the Performance • Performance of FODS depends on the geometrical and fabrication parameters of FODS. • Geometry of the FODS affects the target value of the desired performance parameter of FODS for instance sensitivity in case of FOD. • Sensor performance also gets affected by these parameters. Thus one has to design a FODS which is immune to noise factor variations. • Taguchi technique is used to optimize the FODS design for immunity to noise factors. 14 Retro-Reflective Fiber Optics Displacement Sensor
  15. 15. ……Continuation • This technique is useful in determining the control factors so that the sensitivity of FODS does not get affected by noise factors and its value will not diverted from the target value. • A parameter having largest signal to noise ratio is identified as significant contributor for achieving the best performance characteristic while others having small signal to noise ratio are considered as insignificant contributors. • A comprehensive design is suggested for getting the best performance. A range of results is suggested along with the expected value taking into account the error. 15 Retro-Reflective Fiber Optics Displacement Sensor
  16. 16. Various Factors and its impacts 1. Effect of Variation Is Horizontal Offset(s): • There is no light entering the receiving fiber for smaller values of distance Z between the fiber end faces and reflector. 16 Retro-Reflective Fiber Optics Displacement Sensor Fig-6.Variation Is Horizontal Offset
  17. 17. …..Continuation • As distance increases the reflected cone starts overlapping the receiving fiber. It shows linear variation in the amount of light entering the receiving fiber and the distance Z. • The rate of overlap of reflected cone to the receiving fiber determines the sensitivity of the sensor. • The total overlap signifies the maximum intensity collected by the receiving fiber. The range of distance Z over which this continues is called the operating range of the sensor. • Thus linear region is important as it decides sensitivity and operating range of the sensor. 17 Retro-Reflective Fiber Optics Displacement Sensor
  18. 18. …..Continuation 2. Effect of Source Fiber Angle (α1) : • If the source fiber is slightly inclined then the reflected cone gets shifted slightly towards the receiving fiber. • This increases the rate of overlap of receiving fiber cone with distance Z. This in turn increases the sensitivity of the sensor. 18 Retro-Reflective Fiber Optics Displacement Sensor Fig-7.Source Fiber Angle
  19. 19. …..Continuation 3. Effect of Variation in Core Radius: • Increase in the core radius of source fiber and receiving fiber causes increase in the amount of light collected by the receiving fiber. • Thus for small change in the distance Z between the fiber end face and reflector causes large change in the amount of light collected by the receiving fiber. • This means that the rate of overlap of receiving fiber with reflected cone increases. • This is obvious because of the increase in the core radius of the source as well as receiving fiber 19 Retro-Reflective Fiber Optics Displacement Sensor
  20. 20. …..Continuation 4. Effect of Variation in h: • The variation in vertical offset h between the source and receiving fibers does not show any significant change in the sensitivity of sensor. • The relative vertical displacement of the two fibers does not cause any variation in the amount oflight intensity received by the receiving fibers. • The occurrence of the maximum received intensity takes place at smaller values of Z for negative offset values and for larger Z values for positive offset values. 20 Retro-Reflective Fiber Optics Displacement Sensor
  21. 21. …..Continuation 5. Effect of Variation in Receiving Fiber Angle (α2): • The inclination of receiving fiber causes shifting of receiving fiber core centre away from the source fiber. • This reduces the overlaparea of the receiving fiber core with the reflected cone. • The effect of variation in receiving fiber angle does not shown any variation in the sensitivity. 21 Retro-Reflective Fiber Optics Displacement Sensor Fig-8. Variation in Receiving Fiber Angle
  22. 22. Advantages • Immunity to electromagnetic interference • Small size • High temperature capability • Ability to isolate the sensor head from the electronic components by very large distances • Ability to multiplex number of sensors along single fiber cable 22 Retro-Reflective Fiber Optics Displacement Sensor
  23. 23. Applications • Detecting a hole on the shaft. • Measuring position of the metal plate. • Checking type of the parts for automotive by measuring size. • Measuring inner diameter of pipe. • Checking contamination of surface of the disk brake. Retro-Reflective Fiber Optics Displacement Sensor 23 Fig-9. Applications
  24. 24. Conclusion • The reflected light from the mirror is coupled back into a fiber from a reflecting surface and this power is compared to a portion of thepower emitted by the same light source. • The beam-through type is based on comparing the transmitted light intensity against that of the launch light which can provide information on the displacement between the probe and the target • Two-fiber retro reflective fiber optic displacement sensor is analyzed for optimized and robust design for best sensitivity. • Taguchi method is used for the analysis. 24 Retro-Reflective Fiber Optics Displacement Sensor
  25. 25. References [1] Supriya S. Patil, A. D. Shaligram “Journal of Sensor Technology Vol.10 No.1”,March 31, 2020 [2] Patil, S.S. and Shaligram, A.D. “Modeling and Experimental Studies on Retro-Reflective Fiber Optic Micro-Displacement Sensor with Variable Geometrical Properties Sensors and Actuators”,A172,428433.(2011) [3] M. V. Alfimov and A. M. Zheltikov, “The figure of merit of a photonic-crystal fiber beam delivery and response-signal collection for nanoparticle-assisted sensor arrays” Laser Phys. Lett. 4 , 363– 367 (2007) [4] Buchade, P.B. and Shaligram, A.D. (2007) Influence of Fiber Geometry on the Performance of Two- Fiber Displacement Sensor. Sensors and Actuators, A136, 199- 204.https://doi.org/10.1016/j.sna.2006.11.020 25 Retro-Reflective Fiber Optics Displacement Sensor
  26. 26. 26 Retro-Reflective Fiber Optics Displacement Sensor

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