Week 4 Chapter 1 Part 3 - Pages 1-78 to 1-1-120 Flashcards
Principles of Transmission
The theory and methodology used to verify appropriate optical fiber performance are the same for both singlemode and multimode optical fibers at any wavelength.
a. True
b. False
a. True
p 1-106
The specifications used for each of the components (e.g., transmitter, receiver, optical fiber, connectors) must correspond to the optical fiber type and wavelength.
Which one of the following optical fiber transmitters is associated with a center wavelength of 850 nm and has a modulation frequency up to 10 GHz?
a. VCSEL
b. Short wavelength laser
c. Laser (LD)
d. Light-emitting diode (LED)
a. VCSEL
p 1-87 Table 1.24
Which of the following is a level of multiplexing used in North America?
a. DS0C
b. DS1C
c. DS2C
d. DS3C
b. DS1C
p 1-121
The levels of multiplexing used in North America are DS0, DS1, DS1C, DS2, and DS3.
The attenuation of light signals is higher for visible light (wavelengths of 400 nm to 700 nm) than for light in the near infrared region (wavelengths of 700 nm to 1600 nm)
a. True
b. False
a. True
p 1-101
E1 Level is capable of handling 30 standard (3100 Hz bandwidth) analog voice channels when standard 64 kb/s PCM is used. 60 voice channels are available if 32 kb/s ADPCM encoding is used.
a. True
b. False
a. True
p 1-124
Is capable of handling 30 standard (3100 Hz bandwidth) analog voice channels when standard 64 kb/s PCM is used. 60 voice channels are available if 32 kb/s ADPCM encoding is used.
Optical fiber spectral width is usually given as the range of wavelengths emitted with an intensity level greater than or equal to:
a. One half of the peak intensity level
b. The peak intensity level
c. The central wavelength
d. Twice the peak intensity level
a. One half of the peak intensity level
p 1-81
Spectral width is usually given as the range of wavelengths emitted with an intensity level greater than or equal to one half of the peak intensity level, referred to as the FWHM spectral width. See Figure 1.25
If 32 kb/s (32,000 b/s) ADPCM encoding is used, a DS1 circuit is capable of simultaneously transporting ___ analog voice channels.
a. 24
b. 48
c. 96
d. 128
b. 48
p 1-121
Is capable of handling 24 standard (3100 Hz bandwidth) analog voice channels when standard 64,000 b/s PCM is used. Forty-eight voice channels are available if 32,000 b/s ADPCM encoding is used.
Rise time is usually measured from ___ percent to ___ percent power level. In simplified discussions, the rise time is assumed to be zero. At high data rates, the rise time becomes significant.
a. 0 , 100
b. 10, 90
c. 20, 85
d. 25, 75
b. 10, 90
p 1-92
Transmitters have bandwidth limitations because they take time to change from a low-power state (logical 0) to a high-power state (logical 1). This period is called the rise time.
Rise time is usually measured from 10 percent to 90 percent power level. In simplified discussions, the rise time is assumed to be zero. At high data rates, the rise time becomes significant.
In an optical fiber system, _____ is the difference between the transmitter average power and the receiver sensitivity.
a. Operating margin
b. System gain
c. Link loss budget
d. Bandwidth
b. System gain
p 1-110
System gain is the difference between the transmitter average power and the receiver sensitivity.
The sensitivity of an optical fiber receiver specifies the maximum power level an incoming signal must have.
a. True
b. False
b. False
p 1-88
The sensitivity of a receiver specifies the MINIMUM power level an incoming signal must have to achieve an acceptable level of performance, which is usually specified as a BER.
The numerical aperture of a 62.5/125 µm multimode optical fiber is approximately:
a. 0.10
b. 0.20
c. 0.275
d. 0.325
c. 0.275
p 1-82 Figure 1.26
A DS2 circuit multiplexes ____ DS1 channels.
a. 2
b. 4
c. 7
d. 24
b. 4
p 1-122
The second full level of multiplexing is DS2, which:
• Typically handles four DS1 channels, for a total of 96 voice channels.
• Employs a 6.312 Mb/s pulse stream.
Also se Table 1.39
When calculating the power penalties for an optical fiber system, if the manufacturer does not specify the operating margin, then use a value of ___ for LEDs.
a. 3 dB
b. 0.5 dB
c. 1 dB
d. 2 dB
d. 2 dB
p 1-111
Variations in the component temperature within the operating range of the system. If the system manufacturer does not specify the operating margin, use value of:
• 2 dB for LEDs.
• 3 dB for lasers.
Dispersion in singlemode optical fiber systems is a function of:
a. Transmitter rise time
b. Spectral width
c. Wavelength
c. Wavelength
p 1-94
Dispersion in singlemode systems is a function of wavelength. It is important that the optical fiber dispersion specification coincides with the operating wavelength range of the transmitter.
The center wavelength of short wavelength lasers is:
a. 1310 nm
b. 1250 nm
c. 900 nm
d. 780 nm
d. 780 nm
p 1-84
