Optical fiber communication presentation


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  • Single mode: Diameter of 8.3 to 10 microns., fairly narrow diameter
    -It will propagate typically 1310 or 1550nm
    -higher transmission rate (up to 50 times more distance than multimode)
    -Cost more than multimode.
    Step-index Multimode fiber
    -made of glass fibers.
    -diameter in the 50 to 100 micron range
    -multiple paths of light can cause signal distortion at the receiving end, result in unclear or incomplete data transmission.
    Plastic optic fiber
    -POF is strong and very difficult to bend.
    -POF is not suitable for long-distance transmission
    -POF transmits very little infrared light
    -It can used for cold lighting or lighting displays of artwork
  • When light enters the area between 2 difference materials it will produce two different indexes of refraction. The light will either entirely reflected or a portion of it will be refracted depending on the angle. If the light can be kept at an angle where it is entirely reflected, it will become trapped inside and transmitted along the fiber.
  • -A light sources, there are two types used today are LED (light emitting diode) and ILD (injection laser diode)
    -ILD have a higher output potential and coupling efficiency, they are suited for long distance transmissions.
    -LED have a lower bandwidth, or information capacity than ILD
  • There are two types of detectors are positive intrinsic negative(PIN) and avalanche photo diodes (APD).
    A PIN can be operational with voltage as low as 5v
    The APD require a large bias between 100v to 300v
  • Optical fiber communication presentation

    2. 2. AGENDA  Introduction  OFS Applications  OFS Capabilities  Advantages  Disadvantages  Fundamental components  Classifications of OFS  Challenges  Conclusion 2
    3. 3. Introduction • Optical sensor is a transducer which converts any form of a signal to an optical signal in the measurable form. • Optical fibers: strands of glass that transmit light over long distances (wire in electrical systems) • Light: transmitted by continuous internal reflections in optical fibers (like electron in electrical systems). 3
    4. 4. Optical fiber sensor system Block Diagram of Optical Fiber Sensor System 4 Optical Tx Optical fibers & Actuators Optical Rx Control system Data Acquisition And health Assessment
    5. 5. What Does F.O.S. Look Like? (Cont’d)  Strain Gage  Embeddable Strain Gage  Pressure Transducer  Displacement Transducer  Temperature Transducer
    6. 6. What Does F.O.S. Look Like? (Cont’d) Various Fiber Optic CensorsVarious Fiber Optic CensorsFiber Optic Shape TapeFiber Optic Shape Tape
    7. 7. OFS Applications Measurement of physical properties such as strain, displacement, temperature, pressure, velocity, and acceleration in structures of any shape or size Monitoring the physical health of structures in real time Damage detection Used in multifunctional structures, in which a combination of smart materials, actuators and sensors work together to produce specific action  “Any environmental effect that can be conceived of can be converted to an optical signal to be interpreted,” Eric Udd, Fiber Optic Censors, John Wiley & Sons, Inc., 1991, p.3 7
    8. 8. Fiber Optic Sensor Capabilities • Rotation, acceleration • Electric and magnetic fields • Temperature and pressure • Acoustics and vibration • Strain, humidity, and viscosity 8
    9. 9. Measured Parameters • Light intensity • displacement (position) • pressure • temperature • strain (rotation and displacement) • flow • magnetic and electrical fields • chemical compositions • velocity, acceleration and vibration • force and stress
    10. 10. Advantages of F.O.S • Lightweight / nonobtrusive • Passive / low power • EMI resistant • High sensitivity and bandwidth • Environmental ruggedness • Complementary to telecom / optoelectronics • Flexible • Non-flammable 10
    11. 11. Disadvantage of fiber optic over copper wire cable • Optical fiber is more expensive per meter than copper • Optical fiber can not be join together as easily as copper cable. It requires training and expensive splicing and measurement equipment. 11
    12. 12. Fundamental Components • Optical fiber • Light sources • Beam conditioning optics • Modulators • Detectors 12
    13. 13. Classification Of Fiber Optics Sensor Systems The above classification of fiber optics sensor system can be explained in following manner: A.Based on Sensor location i. Intrinsic ii. Extrinsic B.Based on operating Principle. i.Based on intensity ii. Based on phase iii. Based on frequency iv. Based on polarization C. According to application i. Physical sensor ii. Chemical sensor iii. Bio-medical sensor 13
    14. 14. Based on Sensor location • INTRINSIC or ACTIVE SENSORS • Physical parameter to be sensed acts directly on the fibre to produce changes in the transmission characteristics • Eg. Pressure and liquid level sensors • EXTRINSIC or PASSIVE SENSORS • Separate sensing element is used and the optical fibre is a waveguide. • Eg. Displacement and laser Doppler velocimeter sensors 14
    15. 15. Extrinsic Fiber Optic Sensors 15 Environmental signal Input fiber Output fiber Light modulator
    16. 16. Extrinsic Fiber Optic Sensors • extrinsic sensors – a coating or a device at the fiber tip performs the measurement.
    17. 17. Intrinsic Fiber Optic Sensors 17 Environmental signal Optical fiber
    18. 18. Intrinsic Fiber Optic Sensors • intrinsic sensors – fiber itself performs the measurement.
    19. 19. Fiber Optic Sensor Principles The general structure of an optical fiber sensor system is shown in Figure aside. It consists of an optical source (Laser, LED, Laser diode etc.), optical fiber, sensing or modulator element (which transduces the measurand to an optical signal), an optical detector and processing electronics (oscilloscope, optical spectrum analyzer etc.). 19
    20. 20. Classification of FOS Based on application areas: • physical sensors (measurement of temperature, strech, etc) • chemical sensors (measurement of pH content, gas analysis, spectroscopic studies, etc.) • biomedical sensors (measurement of blood flow , glucose content, etc.)
    21. 21. Optical Fiber Structure 21 n (clad) n (core) Waveguide axis Numerical aperture
    22. 22. There are three types of fiber optic cable commonly used Single Mode Step-index Multimode fiber Plastic optic fiber Fiber media Optical fibers are the actual media that guides the light
    23. 23. How Does fiber optic transmit light
    24. 24. SNELL’S LAW: n1 sin ϑ = n2 sin ϑ where n is refractive index Optical Fiber • Guidance is achieved through multiple reflections at the fiber walls. • Core, transparent dielectric material, surrounded by another dielectric material with a lower refractive index called cladding. (n1 >n2) • In practice, there is a third protective layer called jacket. n1 n2 ϑ1 ϑ2
    25. 25. Ray Transmission through an Optical Fiber Critical angle of reflection (sin ϑc = n2 /n1)
    26. 26. Fiber Optic Sensors Basic Components: • source of light • a length of sensing (and transmission) fiber • a photo-detector •demodulator • processing and display optics • required electronics
    27. 27. The loss of fiber optic • Material obsorption • Material Scattering • Waveguide scattering • Fiber bending • Fiber coupling loss
    28. 28. A Light Sources LED (Light emitting diode) ILD (injection laser diode)
    29. 29. Detectors •Detector is the receiving end of a fiber optic link. There are two kinds of Detectors 1. PIN (Positive Intrinsic Negative) 2. APD (Avalanche photo diodes) PIN APD
    30. 30. Idea of Modulation • When sending information by an optical fiber, the information must be encoded or transformed somehow into information that capable of being transmitted through a fiber. The signal needs to be modulated. There are two types of modulation Analog and digital.
    31. 31. Fiber Optic Strain Sensors A. Intensity Modulated Strain Gages • Reflective sensors – One bundle is used to transmit the light to a reflecting target – Other collects the reflected light and transmits to a detector –Any movement of the target will effect the intensity of the reflected light.
    32. 32. –Plain reflective displacement sensors have a limited dynamic range of about 0.2 in. – Can be improved by a lens system to 5 in. – sensitive to the orientation and contamination of the reflective surface Fiber Optic Strain Sensors
    33. 33. Fiber Optic Strain Sensors A. Intensity Modulated Strain Gages • Micro-bend Sensors – If a fiber is bent, a portion of the trapped light is lost through the wall.
    34. 34. Fiber Optic Strain Sensors B. Phase Modulated Strain Gages • Fabry-Perot Interferometers (FPI) – light source is conveyed via an optical fiber to two mirrors (reflectors). –When the displacement between the mirrors has changed due to strain, optical spectrum changes – absolute distance between the mirrors gives the strain.
    35. 35. Fiber Optic Strain Sensors –Extremely sensitive –provides point-sensing capability –excellent mechanical properties –output is easy to process –difficult to make rugged enough for harsh construction env. (embedding in concrete)
    36. 36. CONCLUSION There are inherent advantages of fiber optic sensors which include their ability to be light in weight, very compact and small in size. Easy to launch light, low ISI, resistance to electromagnetic interference, high sensitivity, wide bandwidth and environmental ruggedness make them widely used in different fields. All these mentioned characteristics make best use of optical fiber as sensor and the networks which are made up of optical fiber are very advantageous in industry for long time investment areas of media access control, security and privacy. 36
    37. 37. End! Thank you listen… 37