First Experiment

1
First Experiment
2
Bells light phone
3
Todays applications

4
Fountain test
5
Flashlight Experiment
6
Unclad fiber
7
Clad and unclad fiber
8
Light into bent fiber
9
Refraction
10
Spectrum (See p 21 text)
11
Units of Measurement

• measure symbol comparison
• Meter m 1.00m 39.37
• Centimeter cm 1 e-2 m .3937 sunflower seed
• Millimeter mm 1e-3 m .03937 grain of sand
• Micron um 1e-6 m 39 e-6 bacterium
• Nanometer nm 1e-9 m 39 e-9 molecule
• Angstrom A 1e-10 m 39 e 10 hydrogen atom
• Hertz Hz, cyc/sec, breathing
• Kilohertz KHz 1e3 cyc/s Music, sound
• Megahertz MHz 1e6 cyc/s AM band
• Gigahertz GHz 1e9 cyc/s Cell Phone
• Terahertz THz 1e12 cyc/s Light

12
Refraction
13
Index of refraction

• n c/v
• n index of refraction
• c speed of light
• v velocity of light in the material
• Material Index (n) Light Velocity km/s
• Vacuum 1.000 300,000
• Air 1.0003 300,000
• Water 1.33 225,000
• Fused Quartz 1.46 205,000
• Glass 1.5 200,000
• Diamond 2.5 120,000

14
Wave front diagram
15
Wagon wheel analogy
16
Critical angle diagram
17
Snells Law

• n1 sin a1 n2 sin a2
• Where
• n1, n2 index of refraction of material 12
• a1 angle of incidence
• a2 angle of refraction

18
Derivation of critical angle

• n1 sin a1 n2 sin a2
• if a2 90o then a1 a1 (critical)
• (any angle of incidence greater than this
  results in reflection not refraction)
• Sin 90o 1 therefore
• n1 sin a1 n2
• sin a1 n2/n1
• a1 arcsin n2/n1

19
Light entry
20
Fiber Optics Communications Advantages and
Disadvantages

• Pros Cons
• High Bandwidth
• Low Loss Mechanically more complex
• Low EMI
• High Isolation Difficult to amplify
• No RF emissions
• Small and Lightweight
• No ESD issues, no sparks (SAFETY)
• Secure, difficult to tap w/o detection

21
Analog vs Digital
22
Serial digital information
23
Bandwidth