FIBER INSTALLATION AND ACTIVATION QUESTIONS
AND ANSWERS
What is the Fiber-optic cable term for optical transport that is restricted to one path
(mode) for light propagation through the core of an optical fiber? - Answers- Single
Mode Fiber
A type of optical fiber with large core diameters which allow multiple modes, or paths,
upon which the optical signal travels is known as what? - Answers- Multi - Mode Fiber
In fiber-optic terminology, what is "window" ? - Answers- Refers to a center optical
wavelength, as well as a range of wavelengths on either side of the center wavelength
What are the four standard optical windows? - Answers- 850 nm, 1,300 nm, 1,550 nm,
and 1,625 nm.
What window is exclusively used for multimode fiber? - Answers- 850 nm
What is an Erbium-doped fiber amplifier (EDFA)? - Answers- An optical amplifier that
uses active erbium-doped fiber and a pump source (laser) to boost or amplify the optical
signal?
What are the three basic components of all fiber-optic communications networks? -
Answers- (1) an optical transmitter with a light source; (2) the optical fiber (3) an optical
receiver with a photodetector.
What does the spectral width of a laser or Light Emitting Diode (LED) define? -
Answers- A measurement for the band of wavelengths over which a laser light source
emits its energy, generally measured in nanometers (Nm) between the half power points
of an optical light sources maximum amplitude at the center frequency Full Width Half
Maximum (FWHM)
Which type of laser is ideal for analog, high speed digital, and optical multiplexing
networks because of its high SNR (signal to noise ratio) and small spectral widths? -
Answers- Distributed Feed Back (DFB) laser
What are the two common types of laser diodes used in fiber optic networks? -
Answers- Distributed Feed Back (DFB) lasers and Fabry-Perot (F-P) lasers
What are two types of optical detector used in fiber-optic networks? - Answers-
Positive-Intrinsic-Negative diode (PIN) & Avalanche Photo Diode (APD)
What are the two methods used to modulate an optical carrier ? - Answers- Direct
Modulation and Indirect Modulation
,How is optimal sensitivity in an optical receiver obtained? - Answers- Efficient Coupling
to the optical fiber to transfer the maximum amount of optical power from the optical
fiber to the receiver.
Why is the positive -intrinsic - negative (PIN) photo-diode the most common type of
photo-diode used in optical receivers? - Answers- It is relatively inexpensive and can be
operated from a standard power supply.
What is the primary difference between an avalanche photo-diode (APD) and a positive-
intrinsic-negative (PIN) photo-diode? - Answers- APD require a higher voltage power
supply and more complex circuitry
What type of electrical detection can improve the sensitivity of an optical reliever by as
much as 20dB? - Answers- Coherent Detection
Which standards organization is considered to be the creator of the world's most
recognized communications standards, known as "recommendations?" - Answers- The
International Telecommunication Union (ITU).
In which component in a fiber-optics communication system do changes to the intensity
of the optical signal occur? - Answers- The optical transmitter.
What characteristic of a fiber-optic cable enhances the security of signals being
transported in the network? - Answers- Fiber optics are typically made of glass which is
a dielectric material which is basically immune to EMI and RFI
What telecommunication standard designation encompasses all things voice, video, and
data? - Answers- ITU Telecommunications Standardization Sector ITU-T
Single -mode fiber-optic cable is optimized to transport which wavelengths? - Answers-
1310 nm & 1550 nm
An optical fiber consists of what three basic parts? - Answers- Core, Cladding, and
Coating
What is a drawback of using Fabry-Perot (F-P) lasers in high-speed data (HSD)
networks? - Answers- The emission of a number of discrete wavelengths or side
modes.
Why are laser diodes most effective when coupled to single mode fiber? - Answers- Its
high coupled power, directionality, and speed.
What are the factors that contribute to an optical receiver's sensitivity? - Answers-
Noise, responsivity, response time, linear response, back reflection, and optical detector
material.
, What is a positive-intrinsic-negative (PIN) diode? - Answers- An optical detector with
current flow that is linear to the intensity of light photons, with one electron/hole pair
created for every absorbed photon until saturation.
What does the amplification process in an avalanche photodiode (APD) introduce into
the electrical output of an optical detector? - Answers- Noise
What functions does the detector in an optical receiver perform? - Answers- Conversion
of an optical carrier to an electrical signal, and demodulation of the modulated optical
carrier.
What happens if the optical signal exceeds the maximum specified input power into a
photodetector? - Answers- Nonlinear operation resulting in distortion, data errors, and
signal loss.
What is a characteristic of light in a laser beam? - Answers- The laser beam consists of
a limited range of wavelengths (monochromatic), with all light waves in phase (coherent
light).
Which architecture and topology today provides voice, video and data services to
thousands of customers? - Answers- HFC architectures and redundant optical ring
topologies
Which new approach to providing video uses video and audio compression technology
over fiber-to-the-x (FTTx) standards to the customer? - Answers- Internet Protocol TV
(IPTV) using video and audio compression technology and using FTTX standards for
providing fiber connectivity at the location.
How are the combined forward broadcast signals, including voice and data carriers,
delivered to hubs and nodes? - Answers- By using 1,310 nm and 1,550 nm AM optical
transmitters.
What is the disadvantage of long amplifier cascades used in some cable TV networks? -
Answers- Cascading restricts how far cable TV signals could travel, primarily due to
operating performance requirements and reliability of service.
What benefits were realized using fiber for the cascade reduction of RF trunk
amplifiers? - Answers- Outage reduction and improved picture quality.
What designation has been given to optical fibers that are used to connect the master
headend with the primary hub? - Answers- The master headend and primary hubs are
connected using primary ring fibers.
What happens to the dense wave division multiplexing (DWDM) signals at the primary
hub locations in preparation for routing to digital receivers? - Answers- At the primary
AND ANSWERS
What is the Fiber-optic cable term for optical transport that is restricted to one path
(mode) for light propagation through the core of an optical fiber? - Answers- Single
Mode Fiber
A type of optical fiber with large core diameters which allow multiple modes, or paths,
upon which the optical signal travels is known as what? - Answers- Multi - Mode Fiber
In fiber-optic terminology, what is "window" ? - Answers- Refers to a center optical
wavelength, as well as a range of wavelengths on either side of the center wavelength
What are the four standard optical windows? - Answers- 850 nm, 1,300 nm, 1,550 nm,
and 1,625 nm.
What window is exclusively used for multimode fiber? - Answers- 850 nm
What is an Erbium-doped fiber amplifier (EDFA)? - Answers- An optical amplifier that
uses active erbium-doped fiber and a pump source (laser) to boost or amplify the optical
signal?
What are the three basic components of all fiber-optic communications networks? -
Answers- (1) an optical transmitter with a light source; (2) the optical fiber (3) an optical
receiver with a photodetector.
What does the spectral width of a laser or Light Emitting Diode (LED) define? -
Answers- A measurement for the band of wavelengths over which a laser light source
emits its energy, generally measured in nanometers (Nm) between the half power points
of an optical light sources maximum amplitude at the center frequency Full Width Half
Maximum (FWHM)
Which type of laser is ideal for analog, high speed digital, and optical multiplexing
networks because of its high SNR (signal to noise ratio) and small spectral widths? -
Answers- Distributed Feed Back (DFB) laser
What are the two common types of laser diodes used in fiber optic networks? -
Answers- Distributed Feed Back (DFB) lasers and Fabry-Perot (F-P) lasers
What are two types of optical detector used in fiber-optic networks? - Answers-
Positive-Intrinsic-Negative diode (PIN) & Avalanche Photo Diode (APD)
What are the two methods used to modulate an optical carrier ? - Answers- Direct
Modulation and Indirect Modulation
,How is optimal sensitivity in an optical receiver obtained? - Answers- Efficient Coupling
to the optical fiber to transfer the maximum amount of optical power from the optical
fiber to the receiver.
Why is the positive -intrinsic - negative (PIN) photo-diode the most common type of
photo-diode used in optical receivers? - Answers- It is relatively inexpensive and can be
operated from a standard power supply.
What is the primary difference between an avalanche photo-diode (APD) and a positive-
intrinsic-negative (PIN) photo-diode? - Answers- APD require a higher voltage power
supply and more complex circuitry
What type of electrical detection can improve the sensitivity of an optical reliever by as
much as 20dB? - Answers- Coherent Detection
Which standards organization is considered to be the creator of the world's most
recognized communications standards, known as "recommendations?" - Answers- The
International Telecommunication Union (ITU).
In which component in a fiber-optics communication system do changes to the intensity
of the optical signal occur? - Answers- The optical transmitter.
What characteristic of a fiber-optic cable enhances the security of signals being
transported in the network? - Answers- Fiber optics are typically made of glass which is
a dielectric material which is basically immune to EMI and RFI
What telecommunication standard designation encompasses all things voice, video, and
data? - Answers- ITU Telecommunications Standardization Sector ITU-T
Single -mode fiber-optic cable is optimized to transport which wavelengths? - Answers-
1310 nm & 1550 nm
An optical fiber consists of what three basic parts? - Answers- Core, Cladding, and
Coating
What is a drawback of using Fabry-Perot (F-P) lasers in high-speed data (HSD)
networks? - Answers- The emission of a number of discrete wavelengths or side
modes.
Why are laser diodes most effective when coupled to single mode fiber? - Answers- Its
high coupled power, directionality, and speed.
What are the factors that contribute to an optical receiver's sensitivity? - Answers-
Noise, responsivity, response time, linear response, back reflection, and optical detector
material.
, What is a positive-intrinsic-negative (PIN) diode? - Answers- An optical detector with
current flow that is linear to the intensity of light photons, with one electron/hole pair
created for every absorbed photon until saturation.
What does the amplification process in an avalanche photodiode (APD) introduce into
the electrical output of an optical detector? - Answers- Noise
What functions does the detector in an optical receiver perform? - Answers- Conversion
of an optical carrier to an electrical signal, and demodulation of the modulated optical
carrier.
What happens if the optical signal exceeds the maximum specified input power into a
photodetector? - Answers- Nonlinear operation resulting in distortion, data errors, and
signal loss.
What is a characteristic of light in a laser beam? - Answers- The laser beam consists of
a limited range of wavelengths (monochromatic), with all light waves in phase (coherent
light).
Which architecture and topology today provides voice, video and data services to
thousands of customers? - Answers- HFC architectures and redundant optical ring
topologies
Which new approach to providing video uses video and audio compression technology
over fiber-to-the-x (FTTx) standards to the customer? - Answers- Internet Protocol TV
(IPTV) using video and audio compression technology and using FTTX standards for
providing fiber connectivity at the location.
How are the combined forward broadcast signals, including voice and data carriers,
delivered to hubs and nodes? - Answers- By using 1,310 nm and 1,550 nm AM optical
transmitters.
What is the disadvantage of long amplifier cascades used in some cable TV networks? -
Answers- Cascading restricts how far cable TV signals could travel, primarily due to
operating performance requirements and reliability of service.
What benefits were realized using fiber for the cascade reduction of RF trunk
amplifiers? - Answers- Outage reduction and improved picture quality.
What designation has been given to optical fibers that are used to connect the master
headend with the primary hub? - Answers- The master headend and primary hubs are
connected using primary ring fibers.
What happens to the dense wave division multiplexing (DWDM) signals at the primary
hub locations in preparation for routing to digital receivers? - Answers- At the primary
