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Unit 3-2


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30.(414) What describes an advantage of using fiber optic cable?
Electromagnetic fields fo not affect fiber optic cables
31.(414) The designation of one-millionth of a meter is
32.(415) Most fiber optic links use infrared light that has a frequency range of about
750 to 1500 nm.
33.(415) What two important facts must be considered when light is propagated through a prism or a fiber?
The refractive index and angle at whcih the light strikes the junction
34.(415) A knowledge of the principles of refraction includes the normal,angle of refraction and
angle of incidence
35.(415) Propagation of light as seen by snells law is known as
total internal reflection
36.(415) How is attenuation measured in fiber optics?
decibels per kilometer
37.(415) The two main causes of attenuation in an optic fiber result from absorption and
rayleigh scattering
38.(416) The most useful way to classify optic fiber cables is by
refractive indes profile and number of modes
39.(416) In fiber optics a "mode" can best be described as
the path light travels down a fiber
40.(416) Which classification type of fiber optical cable has the highest dispersion throughout its length?
Multimode step-index
41.(416) A fiber optic cable in which the core has numerous concentric layers of glass is classified as
multimode graded-index
42.(417) What type of buffer allows the fiber optic cable to be twisted or pulled with little stress on the fiber?
Loose tube
43.(417) What outer jacket material used on fiber optic cables has a low resistance to sunlight and abrasion?
polyvinyl chloride
44.(417) The basic building block of a breakout cable is known as the
45.(418) What components make up a complete basic fiber optic link(exclude fiber connections)?
Driver,source,optic fiber,detector,and an output circuit
46.(418) Two types of light sources for fiber optic modems are light-emitting diodes and
semiconductor laser diodes
47.(418) What is one of the requirements a light source must have to be beneficial?
Risetime must be fast enough to meet bandwidth requirement
48.(418) What type of emmitter has an "etched well" created in the N-type gallium aluminum arsenide?
49.(418) What is the PN junction called in a light emmitting diode where photons are emanted?
Depletion region
50.(419) What type of current is producted by a photdetector when no light is present?
51.(419) The responsivity of a photodetector is dependent on the
risetime of emitter
52.(419) What photodetector converts one photon to one electron?
Positive intrinsic negative
53.(420) Which fiber optic cable configuration consists of multiber cables?
Breakout cables
54.(420) Which fiber optic connectors do not have a keying device?
Sub-miniature,type A
1.1[414]Who demonstrated principles of total internal reflection?
John Tyndall
1.2[414] Who showed how modulatied light could carry speech?
Alexander Bell
1.3[414] Who demonstrated the laser?
Ted Namon
1.4[414] Light amplification by the stimulated emission of radiation.
1.5[414] Produced the 1st 20db/km fiber
Corning Glass Works
1.6[414] Power losses
1.7[414] First city to use all fiber optics
1.8[414] Information-carrying frequency
1.9[414] Fiber is immune from ______ because the fiber is a dielectric
1.10[414] Based on multiples of 10
1.11[414] One million Hertz
Megahertz (MHz)
1.12[414] One millionth of a meter
1.13[414] One billionth of a meter
1.14[414] Impossible to tap
1.15[414] Protection against fragments of silica
Eye protection
1.16[414] one thousandth of a meter
1.[415] Photon particles are a part of what spectrum?
electromagnetic spectrum
2.[415] What characteristic of the carrier wave does the energy possessed by the photon determine?
the frequency
3.[415] What si teh frequency range of infrared light?
750 to 1,500 nm
4.[415] As light penetrates a prism, what 2 considerations must be studied in the theory of light propagation?
the refractive index and the angle at which light strikes the junction of the material
5.[415] describe refractive index
its the ratio of the speed of light in a vacuum to its speed in a given medium
6.[415] What are the three basic facts to consider in understanding refraction?
the normal(imaganary line perpendicular to the interface of the 2 materials), the angle of incidence (between the normal and he incident ray), and teh angle of refraction (between the refracted ray and the normal in the second material)
7.[415] What happens to light when it passes from a higher-index material to a lower one?
It is bent away from the normal
8.[415]What does Snell's law state?
If a ray of light impedes a junction of two media of different refractive indices beyond he critical angle, the light will be totally internally reflected.
9.[415] Describe numerical aperture.
Its a fiber's light-gathering capability
10.[415] How is light affected in a cable that has a large numerical aperture?
Disperion is increased
11.[415] How does a fiber reach equilibrium-mode distribution?
over distance
12.[415] How is power expressed a fiber optic link?
Microwatts and milliwatts
13.[415] What attributes to fiber-to-fiber connection power losses?
Acceptance cone/ejection cone mismatches, fiber core diameter mismatches, connector insertion loss, and intrinsic fiber loss
14.[415] What unit of measurement is used for fiber optic attenuation?
Decibles per kilometer(db/km)
15.[415] What are the 2 main causes of attenuation in optical fibers?
Absorption and Rayleigh scattering
16.[415] What is spectral attenuation?
It is related to light wavelenths and requires careful balancing of light sources and fibers.
17.[415] How can you reduce Fresnel losses in a fiber?
use index-matching fluids
18.[415] What does nuclear radiation cause in fiber optic cables?
attenuation is increaes by absorption and scattering
19.[415] What happens when a fiber's bending radius is exceeded?
Macrobends and microbends
20.[415] What is disperison in a fiber optic cable?
the spreading out of light in a fiber
21.[415] How does disperion affect the bandwidth?
it limits the bandwidth
22.[415] What causes each of the two main types of disperions?
Modal dispersion is caused by the different paths of light in varous modes, and material dispersion results from different velocities of different wavelenths
23.[415]How is dispersion measured?
Nanoseconds per kilometer

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