Optical Fiber Production: From Silica Purification to Fiber Drawing, Slides of Materials science

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Advanced processing and Optical Fibers

• Optical Fiber Processing
  • Initial tube
  • CVD of core
  • Sintering and annealing
  • coating
  • Applications
• Upcoming Test 1

Fiber Optic Concept

• Cu wires are great for transmitting current.
• They aren’t so good for transmitting multiple independent data streams (voice, video, etc). - Adjacent wires interact and degrade each other’s signal. - They are expensive to maintain. - The signal must be detected, cleaned up, amplified, and sent again often.
• Fiber optics may be the solution.
  • Multiple signals can be transmitted on a signal cable simultaneously.
  • Light does not interfere with itself in the same way that electrons do.
• But, how do we make an optical fiber?
  • Ultra pure core glass, surrounded by
  • Flaw free cladding glass, surrounded by
  • Continuous protective polymer coating (or coatings), bundled with
  • Tens or hundreds of other fibers, protected by
  • Corrosion resistant outer jacket for structural integrity and handling protection. Docsity.com

CVD of optical fibers

• Prepare a silica tube (glass extrusion).
• Heat the tube
• Inject SiCl 4 and O 2 into the tube
• At the heated portion, the SiCl 4 is

oxidized

• UItra pure SiO 2 is deposited on the inner walls of the tube
• Draw the tube through the furnace,

continuously coating the inner walls.

• SiO 2 particles deposit and sinter along the tube, leaving a hollow core [for now].

SiCl (^) 4 O 2 SiO 2 2 Cl 2 heat

•  → +

Fiber drawing and protecting

• Anneal the multiwalled tube to the glass softening temperature.
  • The tube and inner coating collapse to a solid, multilayered rod.
• Fire the rod at an even higher temperature softening it further.
  • Draw the fiber through a nozzle, thinning the fiber dramatically.
  • Core diameters from <5 to 500 um are used.
• Polymer coatings must also be applied.
• Fibers are finally bundled.

Fiber optic diameter

• Plastic fiber has a core diameter of up to 900 um.
  • 20-30 feet max length.
  • Easy to work with.
  • Cheap.
• Glass fibers have cores from 8 to 62.5 um across.
  • Connecting two fibers end-to-end is the hardest par—requires a microscope or an automatic connection of some kind.

Fiber testing

• Fibers must generally pass the following tests
  • Tensile strength greater than 100,000 lb/in 2
  • Dimensional tolerance
  • Temperature dependence
  • Optical properties

Repeating Stations

• Repeating stations are generally placed at regular

distances along a fiber network to detect and amplify the

signals since loss will occur over km, or hundreds of km, of

fiber.

• When light drops to 95% of transmission, a repeating station is required.
• Since the cost of the repeaters is high compared to fiber, tremendous effort goes into making pure, flaw free optical fibers.
• Repeating stations today are generally 100 km apart for major fiber bundles (trans-oceanic, etc).

http://www.telebyteusa.com/foprimer/foch2.htm Docsity.com

Future fiber optic manufacturing?

• Why bother purifying Si and the trouble of making pure and

flaw-free fiber optics when a spider does it naturally?

http://www.newscientist.com/article.ns?id=dn3522 Docsity.com

Lecture 4

• Use of phase diagrams
• Use of the lever rule
• Partial stabilization of zirconia

Lecture 5

• Compressive versus tensile stresses
• How to measure mechanical properties of ceramics (why different from metals/polymers?)
• Measure/Calculate Elastic Modulus
• Measure/Calculate flexural strength. Is this higher or lower than tensile strength?
• Why are ceramic components are not as strong as expected from theory?
• Options to strengthen a polycrystalline/single crystal ceramic.
• Calculate fracture toughness
• Draw a Weibull curve and explain its significance; method to guarantee a part from failing.
• Mechanism for delayed fracture

Lecture 6

• Name 2 additives in glass
• Viscosity vs. Temperature for glass; roughly where is the annealing range and where is the working range
• How to, and why does one, temper glass?
• Glass ceramics--how to prepare, and what advantage does a glass ceramic offer over a normal glass?
• Describe how porcelain and other ceramics are manufactured (slip, form/cast/press, dry, sinter, vitrification).
• What is vitrification? How is it used to strengthen a ceramic part? Lecture 7
• Describe how ceramics are manufactured from powders (powder, press, sinter, diffusion)
• Describe how concrete is manufactured (cement, water, particles, chemical reaction)
• For cement, sketch and explain both the heat evolution vs. time, and strength vs. time.
• How do you select a composition from a phase diagram for a refractory (highest temperature possible, least liquid possible!)

SUMMARY

• Optical Fiber Processing
  • Initial tube
  • CVD of core
  • Sintering and annealing
  • coating
  • applications

Preparation for Test 1 and reading for next class:

Exam Prep (this presentation and web site) Optical Fibers (this presentation, download from web site) Environmental Effect of Materials Processing (download from the web site)