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Transcript of Fiber optics
Fiber Optics Fiber Optics
IntroductionIntroduction
You hear about fiber-optic cables whenever You hear about fiber-optic cables whenever people talk about the people talk about the telephone systemtelephone system, the , the cable TV systemcable TV system or the Internet. or the Internet.
Fiber-optic lines are strands of optically pure Fiber-optic lines are strands of optically pure glassglass as thin as a human hair that carry as thin as a human hair that carry digital information over long distances. digital information over long distances.
They are also used in medical imaging and They are also used in medical imaging and mechanical engineering inspection. mechanical engineering inspection.
What are Fiber Optics? What are Fiber Optics?
Fiber opticsFiber optics (optical fibers) are (optical fibers) are long, thin strands of very pure glass long, thin strands of very pure glass about the diameter of a human hair. about the diameter of a human hair.
They are arranged in bundles called They are arranged in bundles called optical cablesoptical cables and used to transmit and used to transmit lightlight signals over long distances. signals over long distances.
What are Fiber Optics? What are Fiber Optics?
If you look closely at a single optical fiber, If you look closely at a single optical fiber, you will see that it has the following you will see that it has the following parts: parts: CoreCore - Thin glass center of the fiber where - Thin glass center of the fiber where
the light travels the light travels CladdingCladding - Outer optical material - Outer optical material
surrounding the core that reflects the light surrounding the core that reflects the light back into the core back into the core
Buffer coatingBuffer coating - Plastic coating that protects - Plastic coating that protects the fiber from damage and moisture the fiber from damage and moisture
Fiber OpticsFiber Optics
plastic jacketglass or plasticcladdingfiber core
TOTAL INTERNAL REFLECTION
What are Fiber Optics? What are Fiber Optics?
Fiber Optic CablesFiber Optic Cables
SOURCE: SURFNET.NL
What are Fiber Optics? What are Fiber Optics?
Single-mode fibersSingle-mode fibers have small cores (about 3.5 have small cores (about 3.5 x 10-4 inches or 9 microns in diameter) and x 10-4 inches or 9 microns in diameter) and transmit infrared transmit infrared laserlaser light (wavelength = 1,300 light (wavelength = 1,300 to 1,550 nanometers). to 1,550 nanometers).
Multi-mode fibersMulti-mode fibers have larger cores (about 2.5 have larger cores (about 2.5 x 10-3 inches or 62.5 microns in diameter) and x 10-3 inches or 62.5 microns in diameter) and transmit infrared light (wavelength = 850 to transmit infrared light (wavelength = 850 to 1,300 nm) from 1,300 nm) from light-emitting diodeslight-emitting diodes (LEDs). (LEDs).
Some optical fibers can be made from Some optical fibers can be made from plasticplastic. . These fibers have a large core (0.04 inches or 1 These fibers have a large core (0.04 inches or 1 mm diameter) and transmit visible red light mm diameter) and transmit visible red light (wavelength = 650 nm) from LEDs. (wavelength = 650 nm) from LEDs.
How Does an Optical Fiber How Does an Optical Fiber Transmit Light? Transmit Light?
Suppose you want to shine a flashlight beam down a Suppose you want to shine a flashlight beam down a long, straight hallway. long, straight hallway.
Just point the beam straight down the hallway -- light Just point the beam straight down the hallway -- light travels in straight lines, so it is no problem. What if the travels in straight lines, so it is no problem. What if the hallway has a bend in it? hallway has a bend in it?
You could place a mirror at the bend to reflect the light You could place a mirror at the bend to reflect the light beam around the corner. beam around the corner.
What if the hallway is very winding with multiple What if the hallway is very winding with multiple bends? bends?
You might line the walls with mirrors and angle the You might line the walls with mirrors and angle the beam so that it bounces from side-to-side all along the beam so that it bounces from side-to-side all along the hallway. This is exactly what happens in an optical hallway. This is exactly what happens in an optical fiber. fiber.
How Does an Optical Fiber How Does an Optical Fiber Transmit Light? Transmit Light?
How Does an Optical Fiber How Does an Optical Fiber Transmit Light? Transmit Light?
The light in a fiber-optic cable travels through the The light in a fiber-optic cable travels through the core (hallway) by constantly bouncing from the core (hallway) by constantly bouncing from the cladding (mirror-lined walls), a principle called cladding (mirror-lined walls), a principle called total internal reflectiontotal internal reflection. .
Because the cladding does not absorb any light Because the cladding does not absorb any light from the core, the light wave can travel great from the core, the light wave can travel great distances. distances.
However, some of the light signal However, some of the light signal degradesdegrades within the fiber, mostly due to impurities in the within the fiber, mostly due to impurities in the glass. The extent that the signal degrades glass. The extent that the signal degrades depends on the purity of the glass and the depends on the purity of the glass and the wavelength of the transmitted light wavelength of the transmitted light
Dense Wave-Division Dense Wave-Division Multiplexing (DWDM)Multiplexing (DWDM)
---
1
2
3
N
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Multiple colors (frequencies) sentthrough the fiber at the same time,more than 100
Each color carries a separate signal
Allows huge bandwidth
Advantages of Fiber OpticsAdvantages of Fiber Optics
Less expensiveLess expensive . . ThinnerThinner Higher carrying capacityHigher carrying capacity Less signal degradationLess signal degradation Light signalsLight signals Low Low
powerpower Digital signalsDigital signals Non-flammableNon-flammable LightweightLightweight FlexibleFlexible Medical imagingMedical imaging - in bronchoscopes, endoscopes, laparoscopes - in bronchoscopes, endoscopes, laparoscopes
Mechanical imagingMechanical imaging - inspecting mechanical welds in - inspecting mechanical welds in pipes and engines (in airplanes, rockets, space shuttles, pipes and engines (in airplanes, rockets, space shuttles, cars) cars)
PlumbingPlumbing - to inspect sewer lines - to inspect sewer lines
How Are Optical Fibers How Are Optical Fibers Made?Made?
Now that we know how fiber-optic systems work Now that we know how fiber-optic systems work and why they are useful -- how do they make and why they are useful -- how do they make them? Optical fibers are made of extremely pure them? Optical fibers are made of extremely pure optical glassoptical glass. .
We think of a glass window as transparent, but the We think of a glass window as transparent, but the thicker the glass gets, the less transparent it thicker the glass gets, the less transparent it becomes due to impurities in the glass. becomes due to impurities in the glass.
However, the glass in an optical fiber has far fewer However, the glass in an optical fiber has far fewer impurities than window-pane glass. impurities than window-pane glass. One company's description of the quality of glass is as One company's description of the quality of glass is as
follows: If you were on top of an ocean that is miles of follows: If you were on top of an ocean that is miles of solid core optical fiber glass, you could see the bottom solid core optical fiber glass, you could see the bottom clearly. clearly.
How Are Optical Fibers How Are Optical Fibers Made?Made?
Making optical fibers requires the Making optical fibers requires the following steps: following steps: Making a preform glass cylinderMaking a preform glass cylinder Drawing the fibers from the Drawing the fibers from the
preformpreform Testing the fibersTesting the fibers
Making the Preform Blank Making the Preform Blank
The glass for the The glass for the preform is made by preform is made by a process called a process called modified modified chemical vapor chemical vapor depositiondeposition (MCVD). (MCVD).
Making the Preform Blank Making the Preform Blank
In MCVD, oxygen is bubbled through solutions of In MCVD, oxygen is bubbled through solutions of silicon chloride (SiCl4), germanium chloride silicon chloride (SiCl4), germanium chloride (GeCl4) and/or other chemicals. (GeCl4) and/or other chemicals.
The precise mixture governs the various The precise mixture governs the various physical and optical properties (index of physical and optical properties (index of refraction, coefficient of expansion, melting refraction, coefficient of expansion, melting point, etc.). point, etc.).
The gas vapors are then conducted to the inside The gas vapors are then conducted to the inside of a of a synthetic silicasynthetic silica or or quartz tubequartz tube (cladding) (cladding) in a special in a special lathelathe. As the lathe turns, a torch is . As the lathe turns, a torch is moved up and down the outside of the tube. moved up and down the outside of the tube.
Making the Preform Blank Making the Preform Blank
The extreme heat from the torch The extreme heat from the torch causes two things to happen: causes two things to happen: The silicon and germanium react with The silicon and germanium react with
oxygen, forming silicon dioxide (SiO2) oxygen, forming silicon dioxide (SiO2) and germanium dioxide (GeO2). and germanium dioxide (GeO2).
The silicon dioxide and germanium The silicon dioxide and germanium dioxide deposit on the inside of the tube dioxide deposit on the inside of the tube and fuse together to form glass and fuse together to form glass
Making the Preform Blank Making the Preform Blank
The lathe turns continuously The lathe turns continuously to make an even coating and to make an even coating and consistent blank. consistent blank.
The purity of the glass is The purity of the glass is maintained by using maintained by using corrosion-resistant plastic in corrosion-resistant plastic in the gas delivery system the gas delivery system (valve blocks, pipes, seals) (valve blocks, pipes, seals) and by precisely controlling and by precisely controlling the flow and composition of the flow and composition of the mixture. the mixture.
The process of making the The process of making the preform blank is highly preform blank is highly automated and takes several automated and takes several hours. After the preform hours. After the preform blank cools, it is tested for blank cools, it is tested for quality control.quality control.
Drawing Fibers from the Drawing Fibers from the Preform Blank Preform Blank
Once the preform blank has Once the preform blank has been tested, it gets loaded been tested, it gets loaded into a into a fiber drawing fiber drawing towertower. .
Diagram of a fiber Diagram of a fiber drawing tower used to drawing tower used to draw optical glass fibers draw optical glass fibers from a preform blank.from a preform blank.
The blank gets lowered into The blank gets lowered into a graphite furnace (3,452 to a graphite furnace (3,452 to 3,992 degrees Fahrenheit 3,992 degrees Fahrenheit or 1,900 to 2,200 degrees or 1,900 to 2,200 degrees Celsius) and the tip gets Celsius) and the tip gets melted until a molten glob melted until a molten glob falls down by gravity. As it falls down by gravity. As it drops, it cools and forms a drops, it cools and forms a thread. thread.
Drawing Fibers from the Drawing Fibers from the Preform Blank Preform Blank
The operator threads the The operator threads the strand through a series of strand through a series of coating cups (buffer coatings) coating cups (buffer coatings) and ultraviolet light curing and ultraviolet light curing ovens onto a tractor-controlled ovens onto a tractor-controlled spool. spool.
The tractor mechanism slowly The tractor mechanism slowly pulls the fiber from the heated pulls the fiber from the heated preform blank and is precisely preform blank and is precisely controlled by using a controlled by using a laser laser micrometermicrometer to measure the to measure the diameter of the fiber and feed diameter of the fiber and feed the information back to the the information back to the tractor mechanism.tractor mechanism.
Fibers are pulled from the Fibers are pulled from the blank at a rate of 33 to 66 ft/s blank at a rate of 33 to 66 ft/s (10 to 20 m/s) and the finished (10 to 20 m/s) and the finished product is wound onto the product is wound onto the spool. It is not uncommon for spool. It is not uncommon for spools to contain more than 1.4 spools to contain more than 1.4 miles (2.2 km) of optical fiber. miles (2.2 km) of optical fiber.
Testing the Finished Optical Testing the Finished Optical FiberFiber
The finished optical fiber is The finished optical fiber is tested for the following: tested for the following:
Tensile strengthTensile strength Refractive index profileRefractive index profile
Fiber geometryFiber geometry AttenuationAttenuation Information carrying Information carrying
capacitycapacity (bandwidth) (bandwidth) Chromatic dispersionChromatic dispersion ) ) Operating Operating
temperature/humidity temperature/humidity rangerange
Temperature dependence Temperature dependence of attenuationof attenuation
Ability to conduct light Ability to conduct light underwaterunderwater
Optical Fiber Capacity Growth Optical Fiber Capacity Growth
1983-20021983-2002
0
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
200
400
600
800
1,000
1,200
1,400
OC-48 OC-192OC-192, 2
OC-48, 40OC-192, 16
OC-48, 96OC-192, 32
OC-192, 48
OC-192, 80
OC-192, 128
1.7 Gb565Mb135Mb
SingleFiber
Capacity(Gigabits/sec)
1 Terabit =
World record ~ 16 terabits per second
Fiber Optic Lines in Central Fiber Optic Lines in Central PhiladelphiaPhiladelphia
SOURCE: CYBERGEOGRAPHY.ORGTELECOM HOTEL
SOURCE: ALCATEL
Submarine Cables in North Submarine Cables in North East AsiaEast Asia