Introduction Fiber Optical Communication
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Transcript of Introduction Fiber Optical Communication
- Slide 1
- Introduction Fiber Optical Communication www.lcsi.com.tw http://www.fiber-optics.info/
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- Industrial & Optical Ethernet www.lcsi.com.tw 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?
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- Industrial & Optical Ethernet www.lcsi.com.tw 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
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- Industrial & Optical Ethernet www.lcsi.com.tw 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..
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- Industrial & Optical Ethernet www.lcsi.com.tw 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
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- Industrial & Optical Ethernet www.lcsi.com.tw 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.
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- Industrial & Optical Ethernet www.lcsi.com.tw 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
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- Industrial & Optical Ethernet www.lcsi.com.tw 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
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- Industrial & Optical Ethernet www.lcsi.com.tw 9 Fiber Optic Connectors Opti-Jack Volition E2000/LX-5 MU MT is a 12 fiber connector for ribbon cable.
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- Industrial & Optical Ethernet www.lcsi.com.tw 10 Fiber Optic Connector Alignment Ferrule -most traditional connector use 2.5 mm ferrule as fiber-alignment mechanism
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- Industrial & Optical Ethernet www.lcsi.com.tw 11 Connector Ferrule Shapes & Polishes Insertion loss is the loss of optical power contributed by adding a connector to a line.
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- Industrial & Optical Ethernet www.lcsi.com.tw 12 Connector and Splice Loss Mechanisms
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- Industrial & Optical Ethernet www.lcsi.com.tw 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.
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- Industrial & Optical Ethernet www.lcsi.com.tw 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.
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- Industrial & Optical Ethernet www.lcsi.com.tw 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
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- Industrial & Optical Ethernet www.lcsi.com.tw 16 Physics of Total Internal Reflection
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- Industrial & Optical Ethernet www.lcsi.com.tw 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
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- Industrial & Optical Ethernet www.lcsi.com.tw 18 Single Mode v.s. Multi Mode Single Mode Multi Mode
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- Industrial & Optical Ethernet www.lcsi.com.tw 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
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- Industrial & Optical Ethernet www.lcsi.com.tw 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
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- Industrial & Optical Ethernet www.lcsi.com.tw 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
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- Industrial & Optical Ethernet www.lcsi.com.tw 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)
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- Industrial & Optical Ethernet www.lcsi.com.tw 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.
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- Industrial & Optical Ethernet www.lcsi.com.tw 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
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- Industrial & Optical Ethernet www.lcsi.com.tw 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
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- Industrial & Optical Ethernet www.lcsi.com.tw 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