Introduction Fiber Optical Communication

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Transcript of Introduction Fiber Optical Communication

  • Slide 1
  • Introduction Fiber Optical Communication
  • Slide 2
  • Industrial & Optical Ethernet 2 Agenda Advantages of Fiber Optics. Fiber-Optic Communications How Does an Optical Fiber Transmit Light? How Are Optical Fibers Made? What You Need to Know? What Do Fiber Optics Benefit Us?
  • Slide 3
  • Industrial & Optical Ethernet 3 How Fiber Optics Work? You hear about fiber-optic cables whenever people talk about the telephone system, the cable TV system or the Internet. Fiber-optic lines are strands of optically pure glass as thin as a human hair that carry digital information over long distances. They are also used in medical imaging and mechanical engineering inspection telephone systemcable TV systemInternet
  • Slide 4
  • Industrial & Optical Ethernet 4 Advantages of Fiber Optics Less signal degradation - The loss of signal in optical fiber is less than in copper wire. Light signals - No interference with those of other fibers in the same cable. Low power - Signals in optical fibers degrade less and need lower-power transmitters. Light weight - An optical cable weighs less than a comparable copper wire cable. Fiber-optic cables take up less space in the ground Thinner - Optical fibers can be drawn to smaller diameters than copper wire. Higher bandwidth The information-carrying capacity of a fiber is greater that that id twisted-pair cable. Digital signals - Optical fibers are ideally suited for carrying digital information, which is especially useful in computer networks. Non-flammable - Because no electricity is passed through optical fibers, there is no fire hazard..
  • Slide 5
  • Industrial & Optical Ethernet 5 Fiber-Optic Communications Optical Fiber Conducts the light signals over a distance. Optical Regenerator - May be necessary to boost the light signal (for long distances) Transmitter Produces and encodes the light signals Optical Receiver Receives and decodes the light signals
  • Slide 6
  • Industrial & Optical Ethernet 6 Transmitter The transmitter is like the sailor on the deck of the sending ship. It receives and directs the optical device to turn the light "on" and "off" in the correct sequence, thereby generating a light signal. Produces and encodes the light signals.
  • Slide 7
  • Industrial & Optical Ethernet 7 Transmitter Light Source Lasers -narrow spectrum 1~3 nm, high speed Gb/s LEDs -10BASE-FL LED 830 ~870 nm, low band width VCSELs are faster, more efficient, and produce a smaller divergence beam than LEDs. Wavelength (infrared, non-visible portions of the spectrum) 1,550 nm-high speed, long distance, single mode loss
  • Slide 8
  • Industrial & Optical Ethernet 8 Fiber Optic Connectors MT-RJ (AMP, Tyco Electronics) SC Subscriber Connector (NTT) LC (Lucent Technology, 1.25 mm ferrule) ST Straight Tip (AT&T Trademark). Small-Form-Factor, SFF connectors
  • Slide 9
  • Industrial & Optical Ethernet 9 Fiber Optic Connectors Opti-Jack Volition E2000/LX-5 MU MT is a 12 fiber connector for ribbon cable.
  • Slide 10
  • Industrial & Optical Ethernet 10 Fiber Optic Connector Alignment Ferrule -most traditional connector use 2.5 mm ferrule as fiber-alignment mechanism
  • Slide 11
  • Industrial & Optical Ethernet 11 Connector Ferrule Shapes & Polishes Insertion loss is the loss of optical power contributed by adding a connector to a line.
  • Slide 12
  • Industrial & Optical Ethernet 12 Connector and Splice Loss Mechanisms
  • Slide 13
  • Industrial & Optical Ethernet 13 Optical Regenerator Signal loss occurs when the light is transmitted through the fiber, especially over long distances Optical Regenerators is spliced along the cable to boost the degraded light signals. Consists of optical fibers with a special coating (doping). Regenerator is a laser amplifier for the incoming signal.
  • Slide 14
  • Industrial & Optical Ethernet 14 Optical Receiver Optical receiver is like the sailor on the deck of the receiving ship. Takes the incoming digital light signals, decodes them and sends the electrical signal to the other user's computer, TV or telephone (receiving ship's captain).computerTVtelephone The receiver uses a photocell or photodiode to detect the light.
  • Slide 15
  • Industrial & Optical Ethernet 15 How Does an Optical Fiber Transmit Light? Shine a flashlight beam down a long, straight hallway Total internal reflection. Light signal degrades within the fiber Signal degrades depends on the purity of the glass and the wavelength of the transmitted light 850 nm = 60 to 75 percent/km 1,300 nm = 50 to 60 percent/km 1,550 nm is greater than 50 percent/km
  • Slide 16
  • Industrial & Optical Ethernet 16 Physics of Total Internal Reflection
  • Slide 17
  • Industrial & Optical Ethernet 17 What are Fiber Optics? Core - Thin glass center of the fiber where the light travels. Cladding - Outer optical material surrounding the core that reflects the light back into the core. Buffer coating - Plastic coating that protects the fiber from damage and moisture. 9/125/250, 62.5/125/250
  • Slide 18
  • Industrial & Optical Ethernet 18 Single Mode v.s. Multi Mode Single Mode Multi Mode
  • Slide 19
  • Industrial & Optical Ethernet 19 Step Index Core v.s. Graded Index Core for Multi Mode Step-index Fiber: Fiber that has a uniform index of refraction throughout the core that is a step below the index of refraction in the cladding Graded-index Fiber: Optical fiber in which the refractive index of the core is in the form of a parabolic curve, decreasing toward the cladding
  • Slide 20
  • Industrial & Optical Ethernet Classes of Fiber Optics Cores diameter Cladding diameter WavelengthLight source Single-mode fibers 5~10 microns125 microns 1,300 to 1,550 nm Laser,VCSEL infrared Multi-mode Step Index fibers 50, 62.5 or above microns 125~140 microns 850 to 1,300 nm LED,,VCSEL infrared Multi-mode Step Index fibers 400~600 microns 230~630 microns 750~2000 microns LED,,VCSEL infrared Multi-mode plastic fibers 750~2000 microns 650 nmLED, visible red
  • Slide 21
  • Industrial & Optical Ethernet 21 How Are Optical Fibers Made? Optical fibers are made of extremely pure optical glass. Making a preform glass cylinder Drawing the fibers from the preform Testing the fibers
  • Slide 22
  • Industrial & Optical Ethernet 22 Making a preform glass cylinder Oxygen is bubbled through solutions of silicon chloride (SiCl4), germanium chloride (GeCl4) and/or other chemicals. Precise mixture governs the various physical and optical properties (index of refraction, coefficient of expansion, melting point, etc.). The gas vapors are then conducted to the inside of a synthetic silica or quartz tube (cladding) in a special lathe As the lathe turns, a torch is moved up and down the outside of the tube. Modified Chemical Vapor Deposition (MCVD)
  • Slide 23
  • Industrial & Optical Ethernet 23 Making a preform glass cylinder The silicon and germanium react with oxygen, forming silicon dioxide (SiO2) and germanium dioxide (GeO2) The silicon dioxide and germanium dioxide deposit on the inside of the tube and fuse together to form glass. The purity of the glass is maintained by using corrosion-resistant plastic in the gas delivery system (valve blocks, pipes, seals) and by precisely controlling the flow and composition of the mixture.
  • Slide 24
  • Industrial & Optical Ethernet 24 Drawing Fibers from the preform blank Graphite furnace (1,900 to 2,200 Celsius) Laser micrometer - Fibers are pulled from the blank at a rate of 33 to 66 ft/s (10 to 20 m/s) measure the diameter of the fiber feed the information back to the tractor
  • Slide 25
  • Industrial & Optical Ethernet 25 Testing the Finished Optical Fiber Tensile strength - Must withstand 100,000 lb/in 2 or more Refractive index profile - Determine numerical aperture as well as screen for optical defects Fiber geometry - Core diameter, cladding dimensions and coating diameter are uniform Attenuation - Determine the extent that light signals of various wavelengths degrade over distance Information carrying capacity (bandwidth) - Number of signals that can be carried at one time (multi-mode fibers) Chromatic dispersion - Spread of various wavelengths of light through the core (important for bandwidth) Operating temperature/humidity range Temperature dependence of attenuation Ability to conduct light underwater - Important for undersea cables
  • Slide 26
  • Industrial & Optical Ethernet 26 What You Need to Know? Transmitter Power -Transmitters are rated in dBm. Receiver Sensitivity -The minimum acceptable value of received power needed to achieve an acceptable BER or performance. Optical Power Budget -Related to transmitter power and receiver sensitivity Delay Budget -propagation factor is 0.67c or 5 ns/m Optical Power Budge