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Optoelectronics Communications

CHAPTER 1. Optoelectronics Communications. School of Computer and Communication Engineering, University Malaysia Perlis (UniMAP). EKT 442: Optoelectronics. Coursework Contribution. COURSE IMPLEMENTATIONS Lecture 3 hours per week for 14 weeks (Total = 42 hours) Laboratory

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Optoelectronics Communications

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  1. CHAPTER 1 Optoelectronics Communications School of Computer and Communication Engineering, University Malaysia Perlis (UniMAP) EKT 442: Optoelectronics

  2. Coursework Contribution • COURSE IMPLEMENTATIONS • Lecture • 3 hours per week for 14 weeks (Total = 42 hours) • Laboratory • 2 hours per week for 14 weeks (Total = 28 hours) • Lecturer: Mr. Hilal A. Fadhil • Office: 1st Floor, House #8A, KKF 34, K.wei- Kuala Perlis • E-mail: hilaladnan@unimap.edu.my • Office tel#: 04-9852639 • HP#: Upon Request • Teaching Engineer: Mr. Matnor+ Ms. Fazilna, matnor@unimap.edu.my • Office: House #A4, KKF 33, Kuala Perlis

  3. Course material Course text book: • “Gerd Keiser, Optical Fiber Communications, 3rd Edition, Mc Graw Hill, 2000 Reference Books: • Joseph C. Palais, Fiber Optic Communications, 5th Edition, Prentice Hall, 2005 • Jeff Hecht, Undestanding Fiber Optics, 5th Edition, Prentice Hall, 2006

  4. Course Outcome Chapter 1-Introduction: Chapter 2: Light Propagation & Transmission Characteristics of Optical Fiber Chapter 3: Optical Components/ Passive Devices Chapter 4: Optical Sources Chapter 5: Light Detectors, Noise and Detection Chapter 6: SYSTEM DESIGN

  5. Introduction For years fiber optics has been merely a system for piping light around corners and into in accessible places so as to allow the hidden to be seen. But now, fiber optics has evolved into a system of significantly greater importance and use. Throughout the world it is now being used to transmit voice, video, and data signals by light waves over flexible hair-thin threads of glass or plastics. Its advantages in such use, as compared to conventional coaxial cable or twisted wire pairs, are fantastic. As a result, light-wave communication systems of fiber optics communication system are one of the important feature for today’s communication. • What are the features of a optical communication system? • Why “optical ” instead of “copper wire ”?

  6. A History of Fiber Optic Technology The Nineteenth Century • John Tyndall, 1870 • water and light experiment • demonstrated light used internal reflection to follow a specific path • William Wheeling, 1880 • “piping light” patent • never took off • Alexander Graham Bell, 1880 • optical voice transmission system • called a photophone • free light space carried voice 200 meters • Fiber-scope, 1950’s

  7. core cladding The Twentieth Century • Glass coated fibers developed to reduce optical loss • Inner fiber - core • Glass coating - cladding • Development of laser technology was important to fiber optics • Large amounts of light in a tiny spot needed • 1960, ruby and helium-neon laser developed • 1962, semiconductor laser introduced - most popular type of laser in fiber optics

  8. The Twentieth Century (continued) • 1966, Charles Kao and Charles Hockman proposed optical fiber could be used to transmit laser light if attenuation could be kept under 20dB/km (optical fiber loss at the time was over 1,000dB/km) • 1970, Researchers at Corning developed a glass fiber with less than a 20dB/km loss • Attenuation depends on the wavelength of light

  9. Optical Wavelength Bands Short band C-band: Conventional Band L-band: Long Band

  10. Fiber Optics Applications • Military • 1970’s, Fiber optic telephone link installed aboard the U.S.S. Little Rock • 1976, Air Force developed Airborne Light Fiber Technology (ALOF) • Commercial • 1977, AT&T and GTE installed the first fiber optic telephone system • Fiber optic telephone networks are common today • Research continues to increase the capabilities of fiber optic transmission

  11. Applications of Fiber Optics • Military • Computer • Medical/Optometric • Sensor • Communication

  12. Military Application

  13. Computer Application

  14. Sensors Gas sensors Chemical sensors Mechanical sensors Fuel sensors Distance sensors Pressure sensors Fluid level sensors Gyro sensors

  15. Medical Application • Endoscope • Eyes surgery • Blood pressure meter

  16. The Future • Fiber Optics have immense potential bandwidth (over 1 teraHertz, 1012 Hz) • Fiber optics is predicted to bring broadband services to the home • interactive video • interactive banking and shopping • distance learning • security and surveillance • high-speed data communication • digitized video

  17. Fiber Optic Fundamentals

  18. Advantages of Fiber Optics • Immunity from Electromagnetic (EM) Radiation and Lightning • Lighter Weight • Higher Bandwidth • Better Signal Quality • Lower Cost • Easily Upgraded • Ease of Installation The main advantages: Large BW and Low loss

  19. Immunity from EM radiation and Lightning: - Fiber is made from dielectric (non-conducting) materials, It is un affected by EM radiation. - Immunity from EM radiation and lightning most important to the military and in aircraft design. - The fiber can often be run in same conduits that currently carry power, simplifying installation. Lighter Weight: • Copper cables can often be replaced by fiber optic cables that weight at least ten times less. - For long distances, fiber optic has a significant weight advantage over copper cable.

  20. Higher Bandwidth • Fiber has higher bandwidth than any alternative available. • CATV industry in the past required amplifiers every thousand feet, when copper cable was used (due to limited bandwidth of the copper cable). • A modern fiber optic system can carry the signals up 100km without repeater or without amplification. Better Signal Quality - Because fiber is immune to EM interference, has lower loss per unit distance, and wider bandwidth, signal quality is usually substantially better compared to copper.

  21. Lower Cost • Fiber certainly costs less for long distance applications. • The cost of fiber itself is cheaper per unit distance than copper if bandwidth and transmission distance requirements are high.

  22. Principles of Fiber Optic Transmission • Electronic signals converted to light • Light refers to more than the visible portion of the electromagnetic (EM) spectrum

  23. Optical power Measurement units: In designing an optical fiber link, it is of interest to establish, measure the signal level at the transmitter, at the receiver,, at the cable connection, and in the cable. Power: Watt (W), Decibel (dB), and dB Milliwatt (dBm). dB: The difference (or ratio) between two signal levels. Used to describe the effect of system devices on signal strength. For example, a cable has 6 dB signal loss or an amplifier has 15 dB of gain. dBm:A signal strength or power level. 0 dBm is defined as 1 mW (milliWatt) of power into a terminating load such as an antenna or power meter.

  24. The Electromagnetic Spectrum • Light is organized into what is known as the electromagnetic spectrum. • The electromagnetic spectrum is composed of visible and near-infrared light like that transmitted by fiber and all other wavelengths used to transmit signals such as AM and FM and television.

  25. Principles of Fiber Optic Transmission • Wavelength - the distance a single cycle of an EM wave covers • For fiber optics applications, two categories of wavelength are used • visible (400 to 700 nanometers) - limited use • near-infrared (700 to 2000 nanometers) - used almost always in modern fiber optic systems

  26. Elements of an Optical Fiber communication • Fiber optic links contain three basic elements • transmitter • optical fiber • receiver Optical Fiber User Input(s) Transmitter Receiver User Output(s) Optical-to-Electrical Conversion Electrical-to-Optical Conversion

  27. Transmitter (TX) • Electrical interface encodes user’s information through AM, FM or Digital Modulation • Encoded information transformed into light by means of a light-emitting diode (LED) or laser diode (LD) Optical Output Electrical Interface Data Encoder/ Modulator Light Emitter User Input(s)

  28. Receiver (RX) • decodes the light signal back into an electrical signal • types of light detectors typically used • PIN photodiode • Avalanche photodiode • made from silicon (Si), indium gallium arsenide (InGaAs) or germanium (Ge) • the data decoder/demodulator converts the signals into the correct format User Output(s) Light Detector/ Amplifier Data Decoder/ Demodulator Electrical Interface Optical Input

  29. Transmission comparison • metallic: limited information and distance • free-space: • large bandwidth • long distance • not private • costly to obtain useable spectrum • optical fiber: offers best of both

  30. Fiber Optic Components

  31. Fiber Optics Cable • Extremely thin strands of ultra-pure glass • Three main regions • center: core (9 to 100 microns) • middle: cladding (125 or 140 microns) • outside: coating or buffer (250, 500 and 900 microns)

  32. A FIBER STRUCTURE

  33. Light Emitters • Two types • Light-emitting diodes (LED’s) • Surface-emitting (SLED): difficult to focus, low cost • Edge-emitting (ELED): easier to focus, faster • Laser Diodes (LD’s) • narrow beam • fastest

  34. Detectors • Two types • Avalanche photodiode • internal gain • more expensive • extensive support electronics required • PIN photodiode • very economical • does not require additional support circuitry • used more often

  35. Interconnection Devices • Connectors, splices, couplers, splitters, switches, wavelength division multiplexers (WDM’s) • Examples • Interfaces between local area networks and devices • Patch panels • Network-to-terminal connections

  36. Manufacture of Optical Fiber

  37. Introductions • 1970, Corning developed new process called inside vapor deposition (IVD) to first achieve attenuation less than 20dB/km • Later, Corning developed outside vapor deposition (OVD) which increased the purity of fiber • Optical fiber was developed that exhibits losses as low as 0.2dB/km (at 1550nm). This seemed to be adequate for any application. • As the Internet expanded, more capacity was needed. Electronics can handle about 40Gbps, but not much more. Researchers developed Dense Wavelength-Division Multiplexing (DWDM) - 80 or more simultaneous data streams can now be combined on a single fiber, each being transmitted at a slightly different color of light

  38. Manufacture of Optical Fiber - MCVD • Modified Chemical Vapor Deposition (MCVD) • another term for IVD method • vaporized raw materials are deposited into a pre-made silica tube

  39. Cont… • Widely adopted to produce very low – loss graded – index fibers. • The glass vapor particles, arising from the reaction of the constituent metal halide gases and oxygen, flow through the inside of a revolving silica tube. • As the SiO2 particles are deposited, they are sintered to a clear glass layer by an oxyhydrogen torch which travels back and forth along the tube. • When the desired thickness of glass has been deposited, the vapor flow is shut off and the tube is heated strongly to cause it to collapse into a solid rod preform. • The fiber that is subsequently drawn from this preform rod will have a core that consists of the vapor deposited material and a cladding that consists of the original silica tube.

  40. Manufacture of Optical Fiber - OVD • Outside Vapor Deposition (OVD) • vaporized raw materials are deposited on a rotating rod • the rod is removed and the resulting perform is consolidated by heating

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