Assessment Test
- The decade that saw the first full-scale commercial application of fiber-optic communication systems was
A. The 1880s
B. The 1920s
C. The 1960s
D. The 1970s
- Which of the following groups describes the components in a fiber-optic link?
A. Transmitter, receiver, optical fiber, decoder
B. Transmitter, receiver, optical fiber, connectors
C. Transmitter, receiver, optical fiber
D. Transmitter, receiver, optical fiber, cabling
- In a fiber-optic link, which component has an input of electrical energy and an output of light energy?
A. Connector
B. Optical fiber
C. Receiver
D. Transmitte
- A 50 percent reduction in signal strength is a loss of ____________________________.
A. 3dB
B. 3dBm
C. 7dB
D. 7dBm
- Refraction is caused by ____________________________.
A. Light changing color as it passes from one medium into another
B. Light changing speed as it passes from one medium into another
C. Light changing frequency as it passes from one medium into another
D. Light changing direction within a single medium
- A Fresnel reflection will occur because light changes ____________________________ as it moves from a material with a given n into a material with a different n.
A. Direction
B. Speed
C. The critical angle
D. The index of refraction
- Listed from innermost to outermost, the components of an optical fiber are
A. Cladding, core, coating
B. Core, cladding, coating
C. Cladding, coating, core
D. Core, coating, cladding
- Modal dispersion is caused when
A. Light escapes into the cladding from the core.
B. Light rays follow different paths along the fiber core.
C. A fiber is split into several parts.
D. Light encounters a break in the fiber.
- For a fiber of a given bandwidth, as the length of the fiber increases, the bandwidth
A. Increases
B. Decreases
C. Does not change
D. Is independent of the length
- Because infrared lasers cannot be seen, they ____________________________.
A. Cannot hurt your eyes
B. Are not useful in fiber optics
C. Are especially dangerous to your eyes
D. Require special instruments
- Which of the following describes the four components of a fiber optic cable?
A. Core, cladding, coating, buffer
B. Fiber, buffer, strength member, jacket
C. Core, buffer, jacket, coating
D. Fiber, buffer, strength member, coating
- Article ____________________________ of the National Electric Code covers optical fiber cables and raceways.
A. 250
B. 660
C. 770
D. 810
- Which part of the connector holds the fiber in place?
A. The ferrule
B. The cap
C. The boot
D. The body
- Which geometry of the connector endface ensures a physical contact (PC) finish?
A. Flat
B. Rough
C. Curved
D. Lensed
- The puck is used to
A. Keep a firm grip on the connector for polishing.
B. Hold down the abrasive material during polishing.
C. Keep the abrasive surface clean.
D. Keep the ferrule perpendicular to the polishing surface.
- Per ANSI/TIA-568-C.3 the strain relief for a single-mode connector should be which color?
A. Aqua
B. Black
C. Blue
D. Beige
- Lasers emit photons that are in phase through a process called ____________________________ emission.
A. Coherent
B. Incoherent
C. Stimulated
D. Spontaneous
- Fiber-optic receivers use a(n) ____________________________ to convert the light energy from the optical fiber into electrical energy.
A. Photoresistor
B. Photodiode
C. Phototransistor
D. LED
- A cable's minimum bend radius specification is greater
A. During installation
B. After installation
C. When the temperature is higher
D. When it is in a cable tray
- A pulling eye is attached to
A. The cable's outer jacket
B. The cable's strength member
C. The fiber
D. The armor
- What is the jacket color of laser-optimized simplex cordage?
A. Orange
B. Slate
C. Blue
D. Aqua
- Hybrid cable as applied to fiber optics combines
A. Loose and tight buffers
B. Single-mode and multimode optical fibers
C. Optical fibers and current-carrying electrical conductors
D. Plastic and glass optical fibers
- A mechanical splice typically ____________________________ uses to reduce or eliminate Fresnel reflections.
A. Epoxy
B. A high-voltage electric arc
C. Index matching gel
D. Isopropyl alcohol
- Only a ____________________________ laser is considered eye safe.
A. Class I
B. Class II
C. Class III
D. Class IV
- The ____________________________ is the laser primarily used in multimode transmitters.
A. DFB
B. VCSEL
C. Fabry-Pérot
D. LED
- Which types of optical fibers should be used for the physical layer when multiple transmitters are operating in parallel?
A. OS1, OS2
B. OS3, OS4
C. OM1, OM2
D. OM3, OM4
- ____________________________ is required to ensure the proper operation of bidirectional fiber-optic communication systems that use separate transmit and receive optical fibers.
A. Common equipment
B. A demarcation point
C. Polarity
D. A first-level backbone
- When is a splice enclosure used?
A. Whenever a fiber has been spliced
B. When a splice must be placed underground
C. When a splice must be placed underwater
D. Splice enclosures are optional.
- What is the purpose of a patch panel?
A. It takes the place of a splice enclosure.
B. It fills a hole where fiber has been installed.
C. It is used to route signals between cables.
D. It provides a permanent link between two pieces of hardware.
- ____________________________ is the administration standard for telecommunications infrastructures.
A. ANSI/TIA-568-C.3
B. ANSI/TIA-606-B
C. ANSI/TIA-568-C.0
D. Article 770
- Optical fiber offers ____________________________ bandwidth and ____________________________ attenuation than twisted-pair or coaxial cable.
A. Less, more
B. Equal, more
C. Greater, more
D. Greater, less
- Encircled flux launch conditions were developed to improve the accuracy of ____________________________ insertion loss measurements.
A. Multimode
B. Single-mode
C. Multimode and single-mode
D. Multifiber
- The ____________________________ is a device that launches a pulse or pulses of light into one end of an optical fiber and records the amount of light energy that is reflected back.
A. Continuity tester
B. OLTS
C. VFL
D. OTDR
- Which broadband technology moves the highest rates of data over the greatest distances?
A. Fiber optics
B. Digital Subscriber Line (DSL)
C. Broadband over Power Lines (BPL)
D. Wi-Fi
- In fiber optics, ____________________________ is typically used to describe the output of a light source.
A. Frequency
B. Wavelength
C. Hertz
D. Kilometers
- Light traveling across a small air gap between two optical fibers will produce ____________________________.
A. Total internal reflection
B. Electromagnetic radiation
C. A Fresnel reflection
D. The Index of Refraction
- The optical trench surrounds the ____________________________ of multimode or single-mode bend-insensitive optical fibers.
A. Core
B. Cladding
C. Coating
D. Buffer
- Which optical fiber designation offers a minimum effective modal bandwidth-length product of 4700 MHz · km?
A. OM1
B. OM2
C. OM3
D. OM4
- What type of bending loss may not be visible when looking at the fiber-optic cable?
A. Macrobend
B. Microbend
C. Intrinsic
D. Attenuation
- The maximum attenuation allowable for OM1 fiber at 850nm is ____________________________.
A. 0.5 dB/km
B. 1.0 dB/km
C. 1.5 dB/km
D. 3.5 dB/km
Answers to Assessment Test
- D. The first full-scale commercial application of fiber-optic communication systems occurred in 1977, when both AT&T and GTE began using fiber-optic telephone systems for commercial customers.
- B. The fiber-optic link requires a transmitter to send the signal, a receiver to capture the signal, optical fiber to carry the signal, and connectors to provide an interface for the optical fiber and the equipment.
- D. In order for a signal to be sent through optical fiber, the transmitter must first convert it from electrical energy into light.
- A. Reducing signal strength by one-half is a 3dB loss.
- B. Refraction, or the change in the direction of light as it changes speed passing from one material into another, is a key component in fiber-optic transmissions.
- B. When light changes speed as it moves from a material with a given index of refraction into a material with a different index of refraction, a Fresnel reflection occurs.
- B. The core is at the center of the optical fiber; the cladding surrounds the core, and the coating surrounds the cladding.
- B. Modal dispersion is caused when light rays follow different paths in the fiber.
- B. Because dispersion increases with the length of the fiber, the usable bandwidth of the fiber decreases as the signal pulses must be kept farther apart to avoid overlapping.
- C. Because infrared lasers are invisible, you cannot know when they are on, even if you are looking directly into a fiber. You should always make sure the fiber is disconnected from the light source before looking into it with your bare eyes or optical instruments.
- B. The core, cladding, and coating of the fiber itself are considered one component of the cable, with the rest being the buffer, strength member, and jacket.
- C. Article 770 of the National Electrical Code defines requirements for optical fiber cables and raceways.
- A. Beginning at the working end of the connector, the ferrule holds the fiber in place. The ferrule must hold the fiber exactly centered in its endface for the best possible connection, so its construction is critical.
- C. To ensure physical contact (PC) between optical fiber ends, the best endface geometry is a convex curve. This curved, or PC finish, ensures that the highest feature or apex on the endface is the center of the optical fiber end.
- D. The polishing fixture, or puck as it is typically referred to, is used to ensure that the ferrule stays perpendicular to the polishing film during the polishing process.
- C. Per ANSI/TIA-568-C.3 the strain relief for a single-mode connector should be blue in color.
- C. Every photon that escapes the optical cavity is a duplicate of the first photon to escape. These photons have the same wavelength, phase relationship, and direction as the first photon. This process of generating light energy is called stimulated emission.
- B. In a fiber-optic receiver, it's the job of the photodiode to convert the light energy received from the optical fiber into electrical energy.
- A. The minimum installation bend radius is the short-term bend radius, and the minimum operational bend radius is the long-term bend radius. The minimum short-term bend radius is actually the larger of the two because of the tensile stresses that may be placed on the cable during installation.
- B. The pulling eye is specially designed to attach to the cable's strength member at one end and a pulling line at the other.
- D. TIA-598-C defines premises cable jacket colors; aqua is the jacket color for laser-optimized multimode optical fiber used for non-military applications.
- B. Hybrid cable, as applied to fiber optics, combines multimode and single-mode optical fibers in one cable. Hybrid cable should not be confused with composite cable, although the terms have been used interchangeably in the past.
- C. A mechanical splice aligns the cleaved optical fibers and holds them in place. Index matching gel inside the mechanical splice reduces or eliminates Fresnel reflections.
- A. Under normal operating conditions, Class I lasers do not producing damaging radiation levels.
- B. Currently, VCSEL multimode transmitters support only 850nm operation with 50/125μm or 62.5/125μm optical fiber. The VCSEL can support data rates as high as 10Gbps.
- D. As defined in IEEE Standard 802.3-2012, Section 6, when multiple transmitters are operating in parallel, multimode OM3 or OM4 optical fiber should be used for the physical layer.
- C. Polarity is required to ensure the proper operation of bidirectional fiber-optic communication systems that use separate transmit and receive optical fibers. It ensures that there is an end-to-end transmission path between the transmitter and the receiver of a channel.
- A. A splice enclosure is used whenever two fibers have been spliced to protect the splice from exposure and strain.
- C. A patch panel is an interconnection point for fiber-optic cables. They allow signals to be routed from one cable to another with a patch cord or jumper.
- B. ANSI/TIA-606-B is the administration standard for telecommunications infrastructures. This document contains detailed information on conventions for labeling optical fiber connections within buildings, datacenters, and between buildings that share a telecommunication network.
- D. Optical fiber offers the highest bandwidth and the least attenuation of any medium currently available.
- A. Encircled flux launch conditions for all multimode insertion loss measurements has been added to IEC 61280-4-1 Edition 2, ANSI/TIA-568-C.0, and ANSI/TIA-526-14-B. The addition of this requirement arose from the need to improve the accuracy of multimode insertion loss measurements.
- D. The OTDR is nothing more than a device that launches a pulse or pulses of light into one end of an optical fiber and records the amount of light energy that is reflected back. It provides a graphical representation of what is happening in the fiber-optic link or cable under test.
- A. Without fiber optics, broadband as we know it today would not exist. No other transmission medium can move the high rates of data over the long distances required to support the global telecommunications system.
- B. Wavelength or frequency can be used to describe electromagnetic energy; however, wavelength is typically used to describe the output of a fiber-optic light source.
- C. A Fresnel reflection occurs when light changes speed as it moves from the optical fiber to the air and from the air to the optical fiber.
- A. The optical trench surrounds the core of the optical fiber. It has a lower refractive index than the core or the cladding.
- D. The minimum effective bandwidth-length product for a 50/125μm laser optimized OM4 multimode optical fiber is 4700MHz · km.
- B. Microbends are small distortions of the boundary layer between the core and cladding caused by crushing or pressure. Microbends are very small and may not be visible when looking at the fiber-optic cable.
- D. ISO/IEC 11801 defines the performance of OM1; the maximum attenuation at 850nm is 3.5dB for a length of one kilometer.