Optical fiber communication presentation

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2. AGENDA Introduction OFS Applications OFS Capabilities Advantages Disadvantages Fundamental components Classifications of OFS Challenges Conclusion 2 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. 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. What Does F.O.S. Look Like? (Contd) Strain Gage Embeddable Strain Gage Pressure Transducer Displacement Transducer Temperature Transducer 6. What Does F.O.S. Look Like? (Contd) Various Fiber Optic CensorsVarious Fiber Optic CensorsFiber Optic Shape TapeFiber Optic Shape Tape 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. Fiber Optic Sensor Capabilities Rotation, acceleration Electric and magnetic fields Temperature and pressure Acoustics and vibration Strain, humidity, and viscosity 8 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. 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. 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. Fundamental Components Optical fiber Light sources Beam conditioning optics Modulators Detectors 12 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. 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. Extrinsic Fiber Optic Sensors 15 Environmental signal Input fiber Output fiber Light modulator 16. Extrinsic Fiber Optic Sensors extrinsic sensors a coating or a device at the fiber tip performs the measurement. 17. Intrinsic Fiber Optic Sensors 17 Environmental signal Optical fiber 18. Intrinsic Fiber Optic Sensors intrinsic sensors fiber itself performs the measurement. 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. 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. Optical Fiber Structure 21 n (clad) n (core) Waveguide axis Numerical aperture 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. How Does fiber optic transmit light 24. SNELLS LAW: n1 sin = n2 sin 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 1 2 25. Ray Transmission through an Optical Fiber Critical angle of reflection (sin c = n2 /n1) 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. The loss of fiber optic Material obsorption Material Scattering Waveguide scattering Fiber bending Fiber coupling loss 28. A Light Sources LED (Light emitting diode) ILD (injection laser diode) 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. 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. 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. 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. 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. 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. 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. 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. End! Thank you listen 37