WDM & Optical Amplifiers
- 1. King Saud University College of EngineeringSaudi Arabia Electrical DepartmentWavelengthDivision Multiplexing(WDM)EE-424 , Summer 2010Prepared By: Tareq Al-Nuaim 427101840ThamerJalalThamer 427105755 Abdullah Al-Khamesah427101730 Ahmad Ismail 427101731
- 4. Optical FiberAn optical fiber is a transparent thin fiber for transmitting information from point to another by using pulses of lights. Optical FiberAn optical fiber is made up of: The coreThe claddingThe buffer coating Together, all of this creates a fiber optic.
- 5. Optical FiberLight is kept in the core of the optical fiber by total internal reflection. This causes the fiber to act as a waveguide.Optical FiberFibers are used instead of metal wires because signals travel along them with less loss and are also immune to electromagnetic interference.
- 6. Although fibers can be made out of either plastic or glass.Optical FiberThe Types of modes in fibers:Single-mode fibers.Multimode fibers.Multimode graded.
- 7. Optical FiberThe optical spectrum is made up of infrared, visible, and ultraviolet lightOptical FiberAt the beginning one optical fiber is used for one wavelength.
- 8. the increase of the bandwidth became a need. Optical FiberLight waves are usually expressed in nanometers or micrometers or angstrom (Ǻ)
- 9. A decrease of only 1 nm increases the frequency by 133 GHzMain Menu
- 12. MultiplexingMultiplexing: is the process of combining multiple signals onto a single transmission link (One path has many channels).
- 13. MultiplexingMultiplexing can be achieved whenever the transmission capacity of a medium linking two devices is greater than the transmission needs of the devices.
- 14. Multiplexing is very useful where it saves time and money, instead of having a link for every channel we can have one link for multiple channels and transmit and receive information without any problems.Most common Types of Multiplexing
- 15. TDMTime-division multiplexing (TDM).TDMTime-division multiplexing (TDM)Generally used for digital information.
- 16. messages occupy all the channel bandwidth but for short time intervals of time.FDMFrequency-division multiplexing (FDM): FDMFrequency-division multiplexing (FDM) Generally used for analog information.
- 17. all signals are transmitted at the same time (all the time) but in different frequency bands.Main Menu
- 20. IntroductionAs data transmission gets more and more heavy, the need of high rate transmission technology is increasing, the target is a high speed high capacity transmission technology.
- 21. These requirements are achieved by using multiplexing in fiber optics, where high speed and great capacity transmission demands are met. Introductionthe increase of the Capacity (BW) became a need.
- 22. A three ways to increase the Capacity :IntroductionIn fiber-optic communications, it is possible to send different wavelength along a single fiber simultaneously. The technology of combining a number of wavelengths onto the same fiber is known as wavelength division multiplexing, or WDM.DefinitionWDM is a technology which multiplexes multiple optical carrier signals on a single optical fiber by using different wavelengths (colors) of laser light to carry different signals.
- 23. WDM puts together multiple signals and sends them at the same time along a fiber, with transmissions taking place at different wavelengths. This turns a single fiber into the virtual equivalent of a handful of fibers. The most modern of these systems allows for much more than a handful of fibers. Â
- 24. WDM
- 25. WDMIt is somewhat similar in nature to frequency-division multiplexing (FDM) processes but instead of frequency we use wavelength.WDMSince wavelength and frequency are tied together through a simple relationship, the two terms describe the same conceptλ = C / FThe frequency increases as the wavelength is shortened. A decrease of only 1 nm increases the frequency by 133 GHz.WDMoperation occurs within two low loss wavelength bands in silica fibers. These include the C- and L- bands. S band could be used sometimes although its not very common.S-Band: (1480-1520 nm)
- 27. L-Band: (1561-1620 nm)Types of WDM:Currently, there are two types of WDM in existence today:CWDM (coarse wavelength division multiplexing)Â Â Â from 4 to 8 wavelengths per fiber, sometimes more. Designed for short to medium-haul networks. The spacing between wavelengths in CWDM is about 10 to 20 nm.DWDM (dense wavelength division multiplexing)Â Â Â A typical DWDM system supports eight or more wavelengths. Designed for long haul networks. The spacing between wavelengths in DWDM is about 1 to 2 nm.
- 28. WDM
- 29. CWDM vs. DWDMCWDM has large wavelength spacing compared to DWDM which has tight wavelength spacing where it fits more channels onto a single fiber, but cost more to implement and operate.
- 30. DWDM is designed for long-haul transmission.
- 31. CWDM can—in principle—match the basic capabilities of DWDM but at lower capacity and lower cost.CWDM vs. DWDM
- 32. CWDM vs, DWDMBackwards as it may seem, DWDM came well before CWDM, CWDM appeared after a market need of technology with affordable prices.
- 33. CWDM enables carriers to respond flexibly to customer needs in metropolitan regions, in other words the point and purpose of CWDM is short-range communications.
- 34. By design CWDM equipment costs much less as compared to DWDM designs.CWDM vs. DWDMCWDM supports fewer channels and doesn’t transmit over long distances because its light signal isn’t amplified, which keeps costs down but also limits maximum propagation distances.
- 35. DWDM systems require complex and expensive equipment. In contrast, CWDM systems are simple and easy to manufacture, and cost much less than DWDM systems. They are also smaller.CWDM vs. DWDM
- 37. WDM SystemsThe system consists of:Optical transmitter and receiver.Optical fiber link.Optical amplifiers(Postamplifier - Inline amplifier - Preamplifier).WDM Multiplexer and Demultiplexer.
- 38. Optical AmplifiersScattering and absorption in optical fibers cause attenuation of light signals, so for the receiver to interpret them properly signals need to be amplified, thus the use of optical amplifiers are essential.
- 39. Optical AmplifiersThree possible applications of optical amplifiers.Optical AmplifiersThe 3 general applications of optical amplifiers:Â 1- PostamplifierBy placing an amplification device immediately after the optical transmitter where it gives a boost to the light level right at the beginning of a fiber link and serves to increase the transmission distance.2- In-line amplifierA simple amplification of the optical signal at periodic locations along the transmission path is used instead of regenerative repeaters since such a link does not necessarily require a complete regeneration of the signal.
- 40. Optical Amplifiers3- PreamplifierA weak optical signal is amplified ahead of the photo detection process, where an optical preamplifier provides a large gain factor and a broad bandwidth so the receiver can detect the signal properly.Â
- 42. optical amplifier typesErbium-Doped Fiber Amplifier (EDFA):Erbium-doped fiber amplifiers is an example of doped fiber amplifiers (DFAs) and is by far the most important fiber amplifiers in the context of long-range optical fiber communications, It is the most common material for long-haul telecommunication applications due to its high power and large gain bandwidth.
- 43. Optical MultiplexerOptical Multiplexer (WDM):An important WDM component is the wavelength multiplexer. The function of this device is to combine independent signal streams operating at different wavelengths onto the same fiber. Many different techniques using specialized components have been devised for combining multiple wavelengths onto the same fiber and separating them at the receiver.
- 44. The technologies for achieving the multiplexing in fiber optics are
- 45. The technologies for achieving the multiplexing in fiber optics1- Thin-film filters (TFFs)
- 46. The technologies for achieving the multiplexing in fiber optics2- Gratings
- 47. The technologies for achieving the multiplexing in fiber opticsThe choice of the technique depends on the application!
- 48. Applications Applications:1. Local-area networks (LANs).2. Metropolitan-area networks (MANs).3. Wide-area networks (WANs) .
- 49. ConclusionWDM makes a huge benefit from the large capacity that provided by the optical fiber.
- 50. it can be used for short or long distance applications.
- 51. it transmits in very high data rates up to 100 Gb/s.
- 52. There are 6 Techniques of achieving the Multiplexing in Fiber Optics.
- 53. There are 3 types of Amplifiers used in the WDM.
- 54. WDM is the future of communication. Main Menu
- 57. Optical AmplifiersOutlineLimitations of Optical Communications.
- 58. Optical Amplifiers and their Types.
- 59. Erbium Doped Fiber Amplifiers.
- 62. Conclusions.Limitations of Optical CommunicationsDispersion: the spreading of optical pulses as they travel in the line which causes inter symbol interference (ISI).Attenuation: caused by the absorption of part of the transmitted power by the medium and the scattering of another part of the transmitted power.These limitations require the use of repeaters
- 63. Difficulty of implementing (repeater required for every mode).high cost of manufacturing.limited bit rates.Limitations of Repeaters
- 64. How to cancel the need for repeaters?Dispersion can be eliminated by the use of dispersion compensators.Attenuation can be compensated by using optical amplifiers.
- 66. 1- Optical Fiber AmplifiersPumping using Laser diode.Active medium doped with rare earth minerals (Erbium, Praseodymium, Thulium, Neodymium…)Large gain (excitation life time 10ms).
- 67. 2- Semiconductor Optical AmplifiersLike optical fiber amplifiers but active medium is doped with semiconductor alloys (Phosphorus, Gallium, Indium and Arsenic).Smaller gain (excitation life time 0.1nS).Cheaper and easier to implement in optical systems.
- 68. 3-Fiber Raman Amplifiers3- Fiber Raman AmplifiersActive medium is the fiber itself.Requires very long distance of active medium.Much smaller gain.Can be used at any wavelength.
- 69. 1.1-Erbium Doped Fiber Amplifier1.1 Erbium Doped Fiber AmplifierThe most commonly used optical amplifier in optical communication systems.This due to their high gain in the optical bandwidth (1530-1565 nm), which common used in communication system.
- 70. Gain is achieved by stimulating the Erbium ions using a laser diode pump at a wavelength of either 980 nm or 1480 nm.After population inversion is achieved, light at 1550 nm is amplified.
- 71. Like lasers, optical amplifiers depend on spontaneous emissions to amplify light signal.This is achieved by using pumping to achieve population inversion.After population inversion is achieved, passing light will cause stimulated emissions and light will be amplified.
- 72. Erbium Doped Fiber Amplifier
- 73. EDFA Performance Depends onThe amount of doping in the fiber.The length and cross section of the Erbium doped fiber.The wavelength of the pumping laser.The power of the pumping laser.The power of the transmitted signal.
- 74. ApplicationsPower Amplifier / BoosterPower amplifiers (booster) are placed directly after the optical transmitter.In-line AmplifierThe in-line amplifier takes a small input signal and boost its for retransmission down the fiber.PreamplifierIt usually adding the optical amplifier prior to the receiver.
- 75. ConclusionsAttenuation can be compensated by using optical amplifiers.
- 76. the best and most commonly used optical amplifiers are the Erbium doped fiber amplifiers.
- 77. This is mainly due to their excellent performance and their fitting to the optical communication wavelength band which is due to the nature of Erbium ions used for doping.Main Menu