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MODULE 6
QUESTION Sound to electrical.
Mircophone
QUESTION Infrasonic.
Less than 20Hz
QUESTION Ultrasonic.
Greater than 20000Hz
QUESTION Min. deviation, longest wavelength.
red
QUESTION Why the sky is blue.
Scattering
QUESTION Why tip of needle is blurred when viewed from screen.
Diffusion of light
QUESTION Min. distance to see an object.
25cm
QUESTION Wavelength sensitive to eyes.
555nm
QUESTION Blackbody emits ___.
No radiation
QUESTION Black body.
Absorb emit
QUESTION Tuning fork placed on a table top.
Loudness inc.
QUESTION Gay Lussac.
Constant volume
QUESTION Axis of ___.
Radius of gyration
QUESTION 3rd most conductive.
Yold
QUESTION Diopter.
4th power
QUESTION Linear momentum is doubled.
4 times KE
QUESTION Reflection of sound.
Echo
QUESTION Classification of compound.
Acid and base
QUESTION Atomic number of Boron.
5
QUESTION Normal body temperature of human.
37ᵒ
QUESTION Proposed that protons and neutrons are concentrated in a nucleus.
Ernest Rutherford
QUESTION Liquid non-metal at normal temperature.
Bromine
QUESTION The branch of optical technology concerned with the transmission of radiant power (light energy) through fibers.
Fiber optics
QUESTION The basic functions of a fiber optic data link.
Convert an electrical input signal to an optical signal, send the optical signal over an optical fiber, and convert the optical signal back to an electric signal.
QUESTION The three parts of a fiber optic data link.
Transmitter, optical fiber, and receiver
QUESTION The decrease in the amount of light reaching the end of the fiber.
Loss
QUESTION In fiber optic systems, designers consider what trade-offs?
Trade-offs in fiber properties, types of connections, optical sources, and detector types in military and subscriber-loop applications.
QUESTION Seven advantages of fiber optics over electrical systems.
Improved system performance, immunity to electrical noise, signal security, electrical isolation, reduced size and weight, environmental protection, and overall system economy
QUESTION The advent of quantum physics successfully explained the photoelectric effect in terms of fundamental particles of energy called.
Quanta
QUESTION What are the fundamental particles of energy (quanta) known as when referring to light energy?
Photons
QUESTION What type of wave motion is represented by the motion of water?
Transverse-wave motion
QUESTION Illustrated as straight lines, showing the direction in which light is travelling at any point.
Light rays
QUESTION Those substances that transmit almost all the light waves falling upon them are said to be.
Transparent
QUESTION Substances through which some light rays can pass, but through which objects cannot be seen clearly because the rays are diffused, are called.
Translucent
QUESTION Those substances that are unable to transmit any light rays are called.
Opaque
QUESTION Typical optical detector materials used for receiver operation in the 850-nm wavelength region.
Silicon(Si), gallium arsenide(GaAs), and gallium aluminum arsenide(GaAlAs)
QUESTION Examples of optical detector materials used for receiver operation in the 1300-nm and 1550-nm wavelength regions.
Germanium(Ge), indium phosphide(InP), and indium gallium arsenide(InGaAs)
QUESTION Output saturation, occurs at input optical power levels typically.
Greater than 1 milliwatt(mW)
QUESTION Typical reverse-bias voltage applied across the active region of an avalanche photodiode(APD).
Over 100 volts
QUESTION Typical semiconductor materials used in the construction of low-noise APDs include.
Silicon(Si), indium gallium arsenide(InGaAs), and germanium(Ge)
QUESTION Typically, semiconductor lasers emit light spread out over an angle of.
10 to 15 degrees
QUESTION The two most common semiconductor materials used in electronic and electro-optic devices.
Silicon(Si) and gallium arsenide(GaAs)
QUESTION Typically LEDs for the 850-nm region are fabricated using.
GaAs and AlGaAs
QUESTION LEDs for the 1300-nm and 1550-nm regions are fabricated using.
InGaAsP and InP
QUESTION Basic LED types used for fiber optic communication systems.
Surface-emitting LED(SLED), edge-emitting LED(ELED), and super luminescent diode(SLD)
QUESTION Preferred optical source for short-distance(0 to 3km), low data-rate fiber optic systems.
SLEDs, and ELEDs
QUESTION Typically, SLEDs operate efficiently for bit rates.
Up to 250 megabits per second(Mb/s)
QUESTION ELEDs may be modulated at rates.
Up to 400 Mb/s
QUESTION SLDs may be modulated at bit rates of.
Over 400 Mb/s
QUESTION In SLEDs, the size of the primary active region is limited to a small circular area of.
20µm to 50µm in diameter.
QUESTION LDs typically can be modulated at frequencies up to.
Over 2 gigahertz(GHz)
QUESTION Electronic coolers used to cool LDs in system applications.
Thermo-electric(TE) coolers
QUESTION For the lowest data rates (0 to 20 megabits per second), sources tend to operate in the.
850-nm window
QUESTION For moderate data rates (50 to 200Mbps), sources tend to operate in the.
1300-nm window
QUESTION Are usually only used in the extremely long distance high-data-rate applications(undersea links, etc).
1550-nm transmitters
QUESTION Typical low-frequency applications are.
Analog audio and single channel video systems
QUESTION Types of systems for moderate frequency applications.
Multi-channel analog audio and video systems as well as frequency modulated(FM) systems
QUESTION Typical high frequency applications are.
Cable television trunk line and raw radar remoting applications
QUESTION Are typically used in cable television trunk line applications.
1550-nm transmitters
QUESTION Electronics industries association / telecommunications industries association.
EIA / TIA
QUESTION For most fiber optic measurements, these standard procedures are documented by the.
EIA / TIA
QUESTION Each component measurement procedure is assigned a unique number given by.
EIA / TIA-526-X
QUESTION The cutback method for measuring multimode fiber attenuation is.
EIA / TIA-455-46
QUESTION The cutback method for measuring single mode fiber attenuation is.
EIA / TIA-455-78
QUESTION Describes how to properly prepare fiber ends for measurement purposes.
EIA / TIA-455-57
QUESTION A 20-mm diameter mandrel is typically used for.
62.5µm fiber
QUESTION Another common mode filter for single mode fibers is.
30-mm diameter circular free-form loop
QUESTION Additional information on multimode and single mode filters(and launch conditions) is available in.
EIA / TIA-455-50 and EIA / TIA-455-57, respectively
QUESTION The test method for uncabled single mode fiber cutoff wavelength is.
EIA / TIA-455-80
QUESTION The test method for cabled single mode fiber cutoff wavelength is.
EIA / TIA-455-170
QUESTION The test method for measuring the bandwidth of multimode fibers in the frequency domain is.
EIA / TIA-455-30
QUESTION Chromatic dispersion is measured in the frequency domain using.
EIA / TIA-455-169 and EIA / TIA-455-175
QUESTION The procedure for measuring multimode and single mode fiber geometry is detailed in.
EIA / TIA-455-176
QUESTION The fiber-geometrical parameters measured include.
Cladding diameter, cladding noncircularity, corecladding concentricity error, and core noncircularity
QUESTION Core diameter is measured using.
EIA / TIA-455-58
QUESTION Describes the procedure for measuring the near-field power distribution of optical waveguides.
EIA / TIA-455-43
QUESTION Output near-field radiation pattern can be obtained by using.
EIA / TIA-455-43
QUESTION The numerical aperture(NA) of a multimode fiber having a near-parabolic refractive index profile is measured using.
EIA / TIA-455-177
QUESTION Describes various procedures, or methods, for measuring the far-field power distribution of optical waveguides.
EIA / TIA-455-47
QUESTION The mode field diameter of a single mode fiber can be measured using.
EIA / TIA-455-167
QUESTION Provides information on the mathematics behind the transformation procedure between the far-field and near-field.
EIA / TIA-455-167
QUESTION Insertion loss of both multimode and single mode interconnection devices is measured using.
EIA / TIA-455-34
QUESTION The mandrel wrap method of measuring the insertion loss of an interconnecting device is included in.
EIA / TIA-455-34
QUESTION Return loss and reflectance are measured using.
EIA / TIA-455-107
QUESTION The fiber optic test method for measuring the attenuation of an installed optical fiber using an optical time-domain reflectometer(OTDR).
EIA / TIA-455-61
QUESTION The group index(N) is provided by fiber manufacturers or is found using.
EIA / TIA-455-60
QUESTION Point defects are located and measured using.
EIA / TIA-455-59
QUESTION The transmission loss of fiber optic cable plants is measured using.
EIA / TIA-526-14 method B (multimode fiber) or EIA / TIA-526-7 (single mode fiber)
QUESTION Fiber inspection is done visually by the use of a standard microscope at.
200 to 400 times magnification
QUESTION Ferrule-type ST® connectors are becoming the commercial connector of choice for local area network(LAN) and data transfer links and are the standard connector for navy light duty applications. This connector is described in specification sheets 16,17, and 18 of.
MIL-C-83522
QUESTION One type of heavy-duty connector designed for use in harsh navy environments is described by the military specification.
MIL-C-28876
QUESTION Standard core sizes for multimode step-index fibers are.
50µm and 100µm
QUESTION Standard core sizes for multimode gradedindex fibers are.
50µm, 62.5µm, 85µm, and 100µm
QUESTION Standard core sizes for single mode fibers are.
Between 8µm, and 10µm
QUESTION Standard multimode graded-index fiber core and cladding sizes are.
50/125µm, 62.5/125µm, 85/125µm, and 100/140µm
QUESTION Typical values of relative refractive index difference(Δ) are around.
0.01 to 0.02
QUESTION An OFCC cable consists of individual single fiber cables, called.
Optical fiber cable components(OFCC)
QUESTION The OFCC outer diameter is typically.
2millimeters(mm)
QUESTION The fiber is typically buffered with a polyester elastomer to a total diameter of.
900µm
QUESTION An OFCC cable of 0.5inch cable outer diameter can accommodate about.
12 fibers
QUESTION OFCC type cable is also being evaluated for use in navy applications with fiber counts up to.
36 fibers(OFCC)
QUESTION Involves calculating the rise times of the link transmitter and the optical fiber.
Risetime budget
QUESTION The composite optical transmitter/fiber risetime is referred to as the.
Fiber exit risetime
QUESTION Consists of all the fiber optic cables and the fiber optic interconnection equipment within the shop, including connectors, splices, and interconnection boxes.
Fiber optic cable plant
QUESTION Optical fibers or cables should never be bent at a radius of curvature less than a certain value, called the.
Minimum bend radius
QUESTION A hybrid device that converts electrical signals into optical signals and launches the optical signals into an optical fiber.
Fiber optic transmitter
QUESTION Two basic types of amplifiers used in fiber optic receivers.
High-impedance amplifiers and transimpedance amplifier
QUESTION Fiber optic receivers can be classified into two categories.
Digital and analog
QUESTION Consists of an optical transmitter, optical fiber, and an optical receiver.
Point to point fiber optic data link
QUESTION A common fiber optic application is the.
Full duplex link
QUESTION Consists of a single transmission line that is shared by a number of equipments.
Linear bus topology
QUESTION Consists of equipments attached to one another in a closed loop or ring.
Ring topology
QUESTION Configuration wherein each equipment is connected a common center hub.
Star topology
QUESTION Consists of a transmission line that branches, or splits.
Tree topology
QUESTION The process of varying one or more characteristics of an optical signal to encode and convey information.
modulation
QUESTION A discontinuous signal that changes from one state to another in discrete steps.
Digital signal
QUESTION A popular form of digital modulation.
Binary modulation
QUESTION The process of arranging symbols that represent binary data in a particular pattern for transmission.
Line coding
QUESTION A continuous signal whose amplitude, phase, or some other property varies in a direct proportion to the instantaneous value of a physical variable.
Analog signal
QUESTION Modulation wherein the intensity of a optical source’s output signal is directly modulated by the incoming electrical analog base band signal.
Intensity modulation
QUESTION A signal that is in its original form and has not been changed by a modulation technique.
Base band signal
QUESTION Involves identifying all of the sources of loss in the fiber optic link.
Power budget
QUESTION The difference between the transmitter output power and the receiver sensitivity is referred to as the.
Available power
QUESTION The ratio of the optical detector’s output photocurrent in amperes to the incident optical power in watts
responsivity
QUESTION A semiconductor positive-negative(p-n) structure with an intrinsic region sandwiched between the other two regions.
PIN photodiode
QUESTION When no light is incident on the photodiode, a current is still produced called.
Dark current
QUESTION The detector thickness is related to the amount of time required for the electrons generated to flow out of the detector active area. This time is referred to as the electron.
Transmit time
QUESTION It is given by tRC=RC
RC time constant
QUESTION Means that the output electrical current(photocurrent) of the photodiode is linearly proportional to the input optical power.
Detector linearity
QUESTION A photodiode that internally amplifies the photocurrent by an avalanche process.
Avalanche photodiode(APD)
QUESTION Occurs when accelerated electrons collide with other electrons in the semiconductor material, causing a fraction of them to become part of the photocurrent.
Avalanche multiplication
QUESTION Defined as the first stage of amplification following the optical detector.
Pre amplifier
QUESTION Defined as the remaining stages of amplification required to raise the detector’s electrical signal to a level suitable for further signal processing.
Post amplifier
QUESTION It includes thermal noise, dark noise, and quantum noise.
Receiver noise
QUESTION The noise resulting from the random motion of electrons in a conducting medium.
Thermal noise
QUESTION Noise caused by current fluctuations because of the discrete nature of charge carriers.
Shot noise
QUESTION Results from dark current that continues to flow in the photodiode when there is no incident light.
Dark current noise
QUESTION Results from the random generation of electrons by the incident optical radiation.
Quantum noise
QUESTION Involves wrapping the test fiber around a mandrel.
Mandrel wrap mode filter
QUESTION The wavelength of a single mode fiber above which the fiber propagates only the fundamental mode.
Cut off wavelength
QUESTION A technique of measuring the cutoff wavelength wherein the same fiber with small bends is used as the reference fiber.
Bend-reference technique
QUESTION A technique of measuring the cut-off wavelength wherein a piece of the multimode fiber is used as the reference fiber.
Multimode-reference technique
QUESTION Causes the spreading of the light pulse as it travels along the fiber.
Dispersion
QUESTION Defined as the average diameter of the cladding.
Cladding diameter
QUESTION Defined as the average diameter of the core.
Core diameter
QUESTION The difference between the smallest radius of the fiber (Rmin) and the largest radius (Rmax) divided by the average cladding radius(R).
Cladding noncircularity, or ellipticity
QUESTION For multimode fibers, it is the distance between, the core and cladding centers divided by the core diameter.
Core-cladding concentricity error
QUESTION The difference between the smallest core radius(Rmin) and the largest core radius(Rmax) divided by the core radius(Rc).
Core noncircularity
QUESTION An electro-optic device that accepts optical signals from an optical fiber and converts them into electrical signals.
Fiber optic receiver
QUESTION The minimum amount of optical power required to achieve a specific receiver performance.
Receiver sensitivity
QUESTION Refers to the range of optical power levels over which the receiver operates within the specified values.
Dynamic range
QUESTION A device that converts input energy of one form into output energy of another.
transducer
QUESTION A transducer that converts an optical signal into an electrical signal.
Optical detector
QUESTION Semiconductor detectors are designed so that optical energy(photons) incident on the detector active area produces a current called.
photocurrent
QUESTION A passive device that distributes optical power from more than two input parts among several output parts.
Star coupler
QUESTION A passive device that splits the optical power from one input fiber to more than two output fibers.
Tree coupler
QUESTION Fiber optic couplers that prevent the transfer of power between input fibers.
Directional couplers
QUESTION Transmits the same amount of power through the coupler when the input and output fibers are reversed.
Symmetrical coupler
QUESTION The loss of optical power as light travels along the fiber.
attenuation
QUESTION Measured by End users at the operating wavelength(λ) of a fiber.
Total attenuation(A)
QUESTION Also known as attenuation rate.
Attenuation coefficient(α)
QUESTION The area of the fiber face illuminated by the light beam from the optical source.
Launch spot size
QUESTION The angular extent of the light beam from the optical source incident on the fiber end face.
Angular distribution
QUESTION Results when the launch spot size and angular distribution are smaller than that of the fiber core.
Underfilled launch
QUESTION Occurs when the launch spot size and angular distribution are larger than that of the fiber core.
Overfilled launch condition
QUESTION A device that removes any cladding mode power from the fiber.
Cladding-mode stripper
QUESTION A device that attenuates specific modes propagating in the core of an optical fiber.
Mode filter
QUESTION One of the most popular splicing techniques in commercial applications.
Electric arc fusion(arc fusion)
QUESTION A short discharge of electric current that prepares the fiber ends for fusion.
prefusion
QUESTION Two basic types of fiber optic connectors.
Butt-joined connectors and expandedbeam connectors
QUESTION Use two lenses to first expanded and then refocus the light from the transmitting fiber into the receiving fiber.
Fiber optic expanded-beam connectors
QUESTION Use two cylindrical plugs(referred to as ferrules), an alignment sleeve, and sometimes axial springs to perform fiber alignment.
Ferrule connectors
QUESTION Two ways that the navy classifies fiber optic connectors.
Light-duty connectors and heavy-duty connectors
QUESTION Redistributes the optical signal without optical-to-electrical conversion.
Passive coupler
QUESTION Electronic devices that split or combine the signal electrically and use fiber optic detectors and sources for input and output.
Active couplers
QUESTION A passive device that splits the optical power carried by a single input fiber into two output fibers.
Optical splitter
QUESTION Normally splits the input optical power evenly between the two output fibers.
Y-coupler
QUESTION A passive device that combines the optical power carried by two input fibers into a single output fiber.
Optical combiner
QUESTION Combines the functions of the optical splitter and combiner.
X-coupler
QUESTION Multiport couplers that have more than two input or two output ports.
Star and tree couplers
QUESTION Caused by a step change in the refractive index that occurs at the fiber joint.
Fresnel reflection
QUESTION Reduces the step change in the refractive index at the fiber interface, reducing Fresnel reflection.
Index matching gel
QUESTION Occurs when a small gap remains between fiber-end faces after completing the fiber connection.
Fiber separation(longitudinal misalignment)
QUESTION Occurs when the axes of the two fibers are off set in a perpendicular direction.
Lateral, or axial misalignment
QUESTION Occurs when the axes of two connected fibers are no longer parallel.
Angular misalignment
QUESTION Some common examples of poor fiber ends.
Fiber-end face tilt, lip, and hackle
QUESTION The basic fiber cleaving technique for preparing optical fibers are coupling.
Score-and-break method
QUESTION Removes most surface imperfections introduced by the fiber cleaving process.
Polishing the fiber ends
QUESTION Occurs when the fiber, mounted to the polishing tool, moves over a 5µ to 15µ grit abrasive paper.
Rough-polishing
QUESTION Occurs when the mounted fiber moves over a 0.3µ to 1µ grit abrasive paper in the same figure-eight motion.
Fine-polishing
QUESTION A source of intrinsic coupling loss.
Fiber mismatches
QUESTION A permanent fiber joint whose purpose is to establish an optical connection between two individual optical fiber.
Fiber optic splice
QUESTION A fiber splice where mechanical fixtures and materials perform fiber alignment and connection.
Mechanical splice
QUESTION A fiber splice where localized heat fuses or melts the ends of two optical fibers together.
Fusion splice
QUESTION Epoxy resins that seal mechanical splices and provide index matching between the connected fibers.
Transparent adhesives
QUESTION It means that the fiber cladding consists of a single homogeneous layer of dielectric material.
Matched cladding
QUESTION It means that the fiber cladding consists of two regions: the inner and outer cladding regions.
Depressed cladding
QUESTION The smallest operating wavelength when single mode fibers propagate only the fundamental mode.
Single mode fiber cutoff wavelength
QUESTION Fibers having a silica glass core and a plastic cladding.
Plastic clad silica (PCS) fibers
QUESTION Method wherein gaseous metal halide compounds, dopant material, and oxygen are oxidized(burned) to form a white silica powder (SiO2).
Vapor phase oxidation
QUESTION Manufacturers call SiO2 the.
soot
QUESTION Method wherein multicomponent glass rods form the fiber structure.
Direct-melt process
QUESTION A tight-buffered fiber surrounded by arimid yarn and a low-halogen outer jacket.
Optical fiber cable components(OFCCs)
QUESTION Makes a permanent joint between two fibers or two groups of fibers.
Fiber optic splice
QUESTION Permit easy coupling and uncoupling of optical fibers.
Fiber optic connectors
QUESTION Distribute or combine optical signals between fibers.
Fiber optic couplers
QUESTION What are the main causes of coupling loss?
Poor fiber end preparation and poor fiber alignment
QUESTION A measure of an optical source’s power launching capability.
Radiance
QUESTION Caused by inherent fiber characteristics.
Intrinsic coupling losses
QUESTION Caused by jointing techniques.
Extrinsic coupling losses
QUESTION A short length of optical fiber (usually 1 meter or less) permanently fixed to the optical source or detector.
Fiber pigtail
QUESTION Waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter.
Reflected waves
QUESTION When a wave approaches a reflecting surface, the wave that strikes the surface is called.
The incident wave
QUESTION When a wave approaches a reflecting surface, the wave that bounces back is called.
The reflected wave
QUESTION An imaginary line perpendicular to the point at which the incident wave strikes the reflecting surface is called.
The normal
QUESTION The angle between the incident wave and the normal.
Angle of incidence
QUESTION The angle between the reflected wave and the normal.
Angle of reflection
QUESTION The angle of incidence is equal to the angle of reflection.
Law of reflection
QUESTION Attenuation is mainly a result of what three properties?
Light absorption, scattering, and bending losses
QUESTION The loss of optical power as light travels along the fiber.
attenuation
QUESTION The portion of attenuation resulting from the conversion of optical power into another energy form, such as heat.
absorption
QUESTION Caused by the electronic transition of metal ions, such as iron, nickel and chromium, from one energy level to another.
Extrinsic absorption
QUESTION Describes the value of refractive index as a function of radial distance at any fiber diameter.
Refractive index profile
QUESTION The refractive index of the core is uniform and undergoes an abrupt change at the corecladding boundary.
Step-index profile
QUESTION The refractive index at the core varies gradually as a function of radial distance from the fiber center.
Graded-index fiber
QUESTION Determines the shape of the core’s profile.
Profile parameter (α)
QUESTION The NA of a multimode graded-index fiber is at its maximum value at the fiber axis. This NA is the.
Axial numerical aperture,NA(O)
QUESTION Sound to electrical.
Mircophone
QUESTION Infrasonic.
Less than 20Hz
QUESTION Ultrasonic.
Greater than 20000Hz
QUESTION Min. deviation, longest wavelength.
red
QUESTION Why the sky is blue.
Scattering
QUESTION Why tip of needle is blurred when viewed from screen.
Diffusion of light
QUESTION Min. distance to see an object.
25cm
QUESTION Wavelength sensitive to eyes.
555nm
QUESTION Blackbody emits ___.
No radiation
QUESTION Black body.
Absorb emit
QUESTION Tuning fork placed on a table top.
Loudness inc.
QUESTION Gay Lussac.
Constant volume
QUESTION Axis of ___.
Radius of gyration
QUESTION 3rd most conductive.
Yold
QUESTION Diopter.
4th power
QUESTION Linear momentum is doubled.
4 times KE
QUESTION Reflection of sound.
Echo
QUESTION Classification of compound.
Acid and base
QUESTION Atomic number of Boron.
5
QUESTION Normal body temperature of human.
37ᵒ
QUESTION Proposed that protons and neutrons are concentrated in a nucleus.
Ernest Rutherford
QUESTION Liquid non-metal at normal temperature.
Bromine
QUESTION The branch of optical technology concerned with the transmission of radiant power (light energy) through fibers.
Fiber optics
QUESTION The basic functions of a fiber optic data link.
Convert an electrical input signal to an optical signal, send the optical signal over an optical fiber, and convert the optical signal back to an electric signal.
QUESTION The three parts of a fiber optic data link.
Transmitter, optical fiber, and receiver
QUESTION The decrease in the amount of light reaching the end of the fiber.
Loss
QUESTION In fiber optic systems, designers consider what trade-offs?
Trade-offs in fiber properties, types of connections, optical sources, and detector types in military and subscriber-loop applications.
QUESTION Seven advantages of fiber optics over electrical systems.
Improved system performance, immunity to electrical noise, signal security, electrical isolation, reduced size and weight, environmental protection, and overall system economy
QUESTION The advent of quantum physics successfully explained the photoelectric effect in terms of fundamental particles of energy called.
Quanta
QUESTION What are the fundamental particles of energy (quanta) known as when referring to light energy?
Photons
QUESTION What type of wave motion is represented by the motion of water?
Transverse-wave motion
QUESTION Illustrated as straight lines, showing the direction in which light is travelling at any point.
Light rays
QUESTION Those substances that transmit almost all the light waves falling upon them are said to be.
Transparent
QUESTION Substances through which some light rays can pass, but through which objects cannot be seen clearly because the rays are diffused, are called.
Translucent
QUESTION Those substances that are unable to transmit any light rays are called.
Opaque
QUESTION Typical optical detector materials used for receiver operation in the 850-nm wavelength region.
Silicon(Si), gallium arsenide(GaAs), and gallium aluminum arsenide(GaAlAs)
QUESTION Examples of optical detector materials used for receiver operation in the 1300-nm and 1550-nm wavelength regions.
Germanium(Ge), indium phosphide(InP), and indium gallium arsenide(InGaAs)
QUESTION Output saturation, occurs at input optical power levels typically.
Greater than 1 milliwatt(mW)
QUESTION Typical reverse-bias voltage applied across the active region of an avalanche photodiode(APD).
Over 100 volts
QUESTION Typical semiconductor materials used in the construction of low-noise APDs include.
Silicon(Si), indium gallium arsenide(InGaAs), and germanium(Ge)
QUESTION Typically, semiconductor lasers emit light spread out over an angle of.
10 to 15 degrees
QUESTION The two most common semiconductor materials used in electronic and electro-optic devices.
Silicon(Si) and gallium arsenide(GaAs)
QUESTION Typically LEDs for the 850-nm region are fabricated using.
GaAs and AlGaAs
QUESTION LEDs for the 1300-nm and 1550-nm regions are fabricated using.
InGaAsP and InP
QUESTION Basic LED types used for fiber optic communication systems.
Surface-emitting LED(SLED), edge-emitting LED(ELED), and super luminescent diode(SLD)
QUESTION Preferred optical source for short-distance(0 to 3km), low data-rate fiber optic systems.
SLEDs, and ELEDs
QUESTION Typically, SLEDs operate efficiently for bit rates.
Up to 250 megabits per second(Mb/s)
QUESTION ELEDs may be modulated at rates.
Up to 400 Mb/s
QUESTION SLDs may be modulated at bit rates of.
Over 400 Mb/s
QUESTION In SLEDs, the size of the primary active region is limited to a small circular area of.
20µm to 50µm in diameter.
QUESTION LDs typically can be modulated at frequencies up to.
Over 2 gigahertz(GHz)
QUESTION Electronic coolers used to cool LDs in system applications.
Thermo-electric(TE) coolers
QUESTION For the lowest data rates (0 to 20 megabits per second), sources tend to operate in the.
850-nm window
QUESTION For moderate data rates (50 to 200Mbps), sources tend to operate in the.
1300-nm window
QUESTION Are usually only used in the extremely long distance high-data-rate applications(undersea links, etc).
1550-nm transmitters
QUESTION Typical low-frequency applications are.
Analog audio and single channel video systems
QUESTION Types of systems for moderate frequency applications.
Multi-channel analog audio and video systems as well as frequency modulated(FM) systems
QUESTION Typical high frequency applications are.
Cable television trunk line and raw radar remoting applications
QUESTION Are typically used in cable television trunk line applications.
1550-nm transmitters
QUESTION Electronics industries association / telecommunications industries association.
EIA / TIA
QUESTION For most fiber optic measurements, these standard procedures are documented by the.
EIA / TIA
QUESTION Each component measurement procedure is assigned a unique number given by.
EIA / TIA-526-X
QUESTION The cutback method for measuring multimode fiber attenuation is.
EIA / TIA-455-46
QUESTION The cutback method for measuring single mode fiber attenuation is.
EIA / TIA-455-78
QUESTION Describes how to properly prepare fiber ends for measurement purposes.
EIA / TIA-455-57
QUESTION A 20-mm diameter mandrel is typically used for.
62.5µm fiber
QUESTION Another common mode filter for single mode fibers is.
30-mm diameter circular free-form loop
QUESTION Additional information on multimode and single mode filters(and launch conditions) is available in.
EIA / TIA-455-50 and EIA / TIA-455-57, respectively
QUESTION The test method for uncabled single mode fiber cutoff wavelength is.
EIA / TIA-455-80
QUESTION The test method for cabled single mode fiber cutoff wavelength is.
EIA / TIA-455-170
QUESTION The test method for measuring the bandwidth of multimode fibers in the frequency domain is.
EIA / TIA-455-30
QUESTION Chromatic dispersion is measured in the frequency domain using.
EIA / TIA-455-169 and EIA / TIA-455-175
QUESTION The procedure for measuring multimode and single mode fiber geometry is detailed in.
EIA / TIA-455-176
QUESTION The fiber-geometrical parameters measured include.
Cladding diameter, cladding noncircularity, corecladding concentricity error, and core noncircularity
QUESTION Core diameter is measured using.
EIA / TIA-455-58
QUESTION Describes the procedure for measuring the near-field power distribution of optical waveguides.
EIA / TIA-455-43
QUESTION Output near-field radiation pattern can be obtained by using.
EIA / TIA-455-43
QUESTION The numerical aperture(NA) of a multimode fiber having a near-parabolic refractive index profile is measured using.
EIA / TIA-455-177
QUESTION Describes various procedures, or methods, for measuring the far-field power distribution of optical waveguides.
EIA / TIA-455-47
QUESTION The mode field diameter of a single mode fiber can be measured using.
EIA / TIA-455-167
QUESTION Provides information on the mathematics behind the transformation procedure between the far-field and near-field.
EIA / TIA-455-167
QUESTION Insertion loss of both multimode and single mode interconnection devices is measured using.
EIA / TIA-455-34
QUESTION The mandrel wrap method of measuring the insertion loss of an interconnecting device is included in.
EIA / TIA-455-34
QUESTION Return loss and reflectance are measured using.
EIA / TIA-455-107
QUESTION The fiber optic test method for measuring the attenuation of an installed optical fiber using an optical time-domain reflectometer(OTDR).
EIA / TIA-455-61
QUESTION The group index(N) is provided by fiber manufacturers or is found using.
EIA / TIA-455-60
QUESTION Point defects are located and measured using.
EIA / TIA-455-59
QUESTION The transmission loss of fiber optic cable plants is measured using.
EIA / TIA-526-14 method B (multimode fiber) or EIA / TIA-526-7 (single mode fiber)
QUESTION Fiber inspection is done visually by the use of a standard microscope at.
200 to 400 times magnification
QUESTION Ferrule-type ST® connectors are becoming the commercial connector of choice for local area network(LAN) and data transfer links and are the standard connector for navy light duty applications. This connector is described in specification sheets 16,17, and 18 of.
MIL-C-83522
QUESTION One type of heavy-duty connector designed for use in harsh navy environments is described by the military specification.
MIL-C-28876
QUESTION Standard core sizes for multimode step-index fibers are.
50µm and 100µm
QUESTION Standard core sizes for multimode gradedindex fibers are.
50µm, 62.5µm, 85µm, and 100µm
QUESTION Standard core sizes for single mode fibers are.
Between 8µm, and 10µm
QUESTION Standard multimode graded-index fiber core and cladding sizes are.
50/125µm, 62.5/125µm, 85/125µm, and 100/140µm
QUESTION Typical values of relative refractive index difference(Δ) are around.
0.01 to 0.02
QUESTION An OFCC cable consists of individual single fiber cables, called.
Optical fiber cable components(OFCC)
QUESTION The OFCC outer diameter is typically.
2millimeters(mm)
QUESTION The fiber is typically buffered with a polyester elastomer to a total diameter of.
900µm
QUESTION An OFCC cable of 0.5inch cable outer diameter can accommodate about.
12 fibers
QUESTION OFCC type cable is also being evaluated for use in navy applications with fiber counts up to.
36 fibers(OFCC)
QUESTION Involves calculating the rise times of the link transmitter and the optical fiber.
Risetime budget
QUESTION The composite optical transmitter/fiber risetime is referred to as the.
Fiber exit risetime
QUESTION Consists of all the fiber optic cables and the fiber optic interconnection equipment within the shop, including connectors, splices, and interconnection boxes.
Fiber optic cable plant
QUESTION Optical fibers or cables should never be bent at a radius of curvature less than a certain value, called the.
Minimum bend radius
QUESTION A hybrid device that converts electrical signals into optical signals and launches the optical signals into an optical fiber.
Fiber optic transmitter
QUESTION Two basic types of amplifiers used in fiber optic receivers.
High-impedance amplifiers and transimpedance amplifier
QUESTION Fiber optic receivers can be classified into two categories.
Digital and analog
QUESTION Consists of an optical transmitter, optical fiber, and an optical receiver.
Point to point fiber optic data link
QUESTION A common fiber optic application is the.
Full duplex link
QUESTION Consists of a single transmission line that is shared by a number of equipments.
Linear bus topology
QUESTION Consists of equipments attached to one another in a closed loop or ring.
Ring topology
QUESTION Configuration wherein each equipment is connected a common center hub.
Star topology
QUESTION Consists of a transmission line that branches, or splits.
Tree topology
QUESTION The process of varying one or more characteristics of an optical signal to encode and convey information.
modulation
QUESTION A discontinuous signal that changes from one state to another in discrete steps.
Digital signal
QUESTION A popular form of digital modulation.
Binary modulation
QUESTION The process of arranging symbols that represent binary data in a particular pattern for transmission.
Line coding
QUESTION A continuous signal whose amplitude, phase, or some other property varies in a direct proportion to the instantaneous value of a physical variable.
Analog signal
QUESTION Modulation wherein the intensity of a optical source’s output signal is directly modulated by the incoming electrical analog base band signal.
Intensity modulation
QUESTION A signal that is in its original form and has not been changed by a modulation technique.
Base band signal
QUESTION Involves identifying all of the sources of loss in the fiber optic link.
Power budget
QUESTION The difference between the transmitter output power and the receiver sensitivity is referred to as the.
Available power
QUESTION The ratio of the optical detector’s output photocurrent in amperes to the incident optical power in watts
responsivity
QUESTION A semiconductor positive-negative(p-n) structure with an intrinsic region sandwiched between the other two regions.
PIN photodiode
QUESTION When no light is incident on the photodiode, a current is still produced called.
Dark current
QUESTION The detector thickness is related to the amount of time required for the electrons generated to flow out of the detector active area. This time is referred to as the electron.
Transmit time
QUESTION It is given by tRC=RC
RC time constant
QUESTION Means that the output electrical current(photocurrent) of the photodiode is linearly proportional to the input optical power.
Detector linearity
QUESTION A photodiode that internally amplifies the photocurrent by an avalanche process.
Avalanche photodiode(APD)
QUESTION Occurs when accelerated electrons collide with other electrons in the semiconductor material, causing a fraction of them to become part of the photocurrent.
Avalanche multiplication
QUESTION Defined as the first stage of amplification following the optical detector.
Pre amplifier
QUESTION Defined as the remaining stages of amplification required to raise the detector’s electrical signal to a level suitable for further signal processing.
Post amplifier
QUESTION It includes thermal noise, dark noise, and quantum noise.
Receiver noise
QUESTION The noise resulting from the random motion of electrons in a conducting medium.
Thermal noise
QUESTION Noise caused by current fluctuations because of the discrete nature of charge carriers.
Shot noise
QUESTION Results from dark current that continues to flow in the photodiode when there is no incident light.
Dark current noise
QUESTION Results from the random generation of electrons by the incident optical radiation.
Quantum noise
QUESTION Involves wrapping the test fiber around a mandrel.
Mandrel wrap mode filter
QUESTION The wavelength of a single mode fiber above which the fiber propagates only the fundamental mode.
Cut off wavelength
QUESTION A technique of measuring the cutoff wavelength wherein the same fiber with small bends is used as the reference fiber.
Bend-reference technique
QUESTION A technique of measuring the cut-off wavelength wherein a piece of the multimode fiber is used as the reference fiber.
Multimode-reference technique
QUESTION Causes the spreading of the light pulse as it travels along the fiber.
Dispersion
QUESTION Defined as the average diameter of the cladding.
Cladding diameter
QUESTION Defined as the average diameter of the core.
Core diameter
QUESTION The difference between the smallest radius of the fiber (Rmin) and the largest radius (Rmax) divided by the average cladding radius(R).
Cladding noncircularity, or ellipticity
QUESTION For multimode fibers, it is the distance between, the core and cladding centers divided by the core diameter.
Core-cladding concentricity error
QUESTION The difference between the smallest core radius(Rmin) and the largest core radius(Rmax) divided by the core radius(Rc).
Core noncircularity
QUESTION An electro-optic device that accepts optical signals from an optical fiber and converts them into electrical signals.
Fiber optic receiver
QUESTION The minimum amount of optical power required to achieve a specific receiver performance.
Receiver sensitivity
QUESTION Refers to the range of optical power levels over which the receiver operates within the specified values.
Dynamic range
QUESTION A device that converts input energy of one form into output energy of another.
transducer
QUESTION A transducer that converts an optical signal into an electrical signal.
Optical detector
QUESTION Semiconductor detectors are designed so that optical energy(photons) incident on the detector active area produces a current called.
photocurrent
QUESTION A passive device that distributes optical power from more than two input parts among several output parts.
Star coupler
QUESTION A passive device that splits the optical power from one input fiber to more than two output fibers.
Tree coupler
QUESTION Fiber optic couplers that prevent the transfer of power between input fibers.
Directional couplers
QUESTION Transmits the same amount of power through the coupler when the input and output fibers are reversed.
Symmetrical coupler
QUESTION The loss of optical power as light travels along the fiber.
attenuation
QUESTION Measured by End users at the operating wavelength(λ) of a fiber.
Total attenuation(A)
QUESTION Also known as attenuation rate.
Attenuation coefficient(α)
QUESTION The area of the fiber face illuminated by the light beam from the optical source.
Launch spot size
QUESTION The angular extent of the light beam from the optical source incident on the fiber end face.
Angular distribution
QUESTION Results when the launch spot size and angular distribution are smaller than that of the fiber core.
Underfilled launch
QUESTION Occurs when the launch spot size and angular distribution are larger than that of the fiber core.
Overfilled launch condition
QUESTION A device that removes any cladding mode power from the fiber.
Cladding-mode stripper
QUESTION A device that attenuates specific modes propagating in the core of an optical fiber.
Mode filter
QUESTION One of the most popular splicing techniques in commercial applications.
Electric arc fusion(arc fusion)
QUESTION A short discharge of electric current that prepares the fiber ends for fusion.
prefusion
QUESTION Two basic types of fiber optic connectors.
Butt-joined connectors and expandedbeam connectors
QUESTION Use two lenses to first expanded and then refocus the light from the transmitting fiber into the receiving fiber.
Fiber optic expanded-beam connectors
QUESTION Use two cylindrical plugs(referred to as ferrules), an alignment sleeve, and sometimes axial springs to perform fiber alignment.
Ferrule connectors
QUESTION Two ways that the navy classifies fiber optic connectors.
Light-duty connectors and heavy-duty connectors
QUESTION Redistributes the optical signal without optical-to-electrical conversion.
Passive coupler
QUESTION Electronic devices that split or combine the signal electrically and use fiber optic detectors and sources for input and output.
Active couplers
QUESTION A passive device that splits the optical power carried by a single input fiber into two output fibers.
Optical splitter
QUESTION Normally splits the input optical power evenly between the two output fibers.
Y-coupler
QUESTION A passive device that combines the optical power carried by two input fibers into a single output fiber.
Optical combiner
QUESTION Combines the functions of the optical splitter and combiner.
X-coupler
QUESTION Multiport couplers that have more than two input or two output ports.
Star and tree couplers
QUESTION Caused by a step change in the refractive index that occurs at the fiber joint.
Fresnel reflection
QUESTION Reduces the step change in the refractive index at the fiber interface, reducing Fresnel reflection.
Index matching gel
QUESTION Occurs when a small gap remains between fiber-end faces after completing the fiber connection.
Fiber separation(longitudinal misalignment)
QUESTION Occurs when the axes of the two fibers are off set in a perpendicular direction.
Lateral, or axial misalignment
QUESTION Occurs when the axes of two connected fibers are no longer parallel.
Angular misalignment
QUESTION Some common examples of poor fiber ends.
Fiber-end face tilt, lip, and hackle
QUESTION The basic fiber cleaving technique for preparing optical fibers are coupling.
Score-and-break method
QUESTION Removes most surface imperfections introduced by the fiber cleaving process.
Polishing the fiber ends
QUESTION Occurs when the fiber, mounted to the polishing tool, moves over a 5µ to 15µ grit abrasive paper.
Rough-polishing
QUESTION Occurs when the mounted fiber moves over a 0.3µ to 1µ grit abrasive paper in the same figure-eight motion.
Fine-polishing
QUESTION A source of intrinsic coupling loss.
Fiber mismatches
QUESTION A permanent fiber joint whose purpose is to establish an optical connection between two individual optical fiber.
Fiber optic splice
QUESTION A fiber splice where mechanical fixtures and materials perform fiber alignment and connection.
Mechanical splice
QUESTION A fiber splice where localized heat fuses or melts the ends of two optical fibers together.
Fusion splice
QUESTION Epoxy resins that seal mechanical splices and provide index matching between the connected fibers.
Transparent adhesives
QUESTION It means that the fiber cladding consists of a single homogeneous layer of dielectric material.
Matched cladding
QUESTION It means that the fiber cladding consists of two regions: the inner and outer cladding regions.
Depressed cladding
QUESTION The smallest operating wavelength when single mode fibers propagate only the fundamental mode.
Single mode fiber cutoff wavelength
QUESTION Fibers having a silica glass core and a plastic cladding.
Plastic clad silica (PCS) fibers
QUESTION Method wherein gaseous metal halide compounds, dopant material, and oxygen are oxidized(burned) to form a white silica powder (SiO2).
Vapor phase oxidation
QUESTION Manufacturers call SiO2 the.
soot
QUESTION Method wherein multicomponent glass rods form the fiber structure.
Direct-melt process
QUESTION A tight-buffered fiber surrounded by arimid yarn and a low-halogen outer jacket.
Optical fiber cable components(OFCCs)
QUESTION Makes a permanent joint between two fibers or two groups of fibers.
Fiber optic splice
QUESTION Permit easy coupling and uncoupling of optical fibers.
Fiber optic connectors
QUESTION Distribute or combine optical signals between fibers.
Fiber optic couplers
QUESTION What are the main causes of coupling loss?
Poor fiber end preparation and poor fiber alignment
QUESTION A measure of an optical source’s power launching capability.
Radiance
QUESTION Caused by inherent fiber characteristics.
Intrinsic coupling losses
QUESTION Caused by jointing techniques.
Extrinsic coupling losses
QUESTION A short length of optical fiber (usually 1 meter or less) permanently fixed to the optical source or detector.
Fiber pigtail
QUESTION Waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter.
Reflected waves
QUESTION When a wave approaches a reflecting surface, the wave that strikes the surface is called.
The incident wave
QUESTION When a wave approaches a reflecting surface, the wave that bounces back is called.
The reflected wave
QUESTION An imaginary line perpendicular to the point at which the incident wave strikes the reflecting surface is called.
The normal
QUESTION The angle between the incident wave and the normal.
Angle of incidence
QUESTION The angle between the reflected wave and the normal.
Angle of reflection
QUESTION The angle of incidence is equal to the angle of reflection.
Law of reflection
QUESTION Attenuation is mainly a result of what three properties?
Light absorption, scattering, and bending losses
QUESTION The loss of optical power as light travels along the fiber.
attenuation
QUESTION The portion of attenuation resulting from the conversion of optical power into another energy form, such as heat.
absorption
QUESTION Caused by the electronic transition of metal ions, such as iron, nickel and chromium, from one energy level to another.
Extrinsic absorption
QUESTION Describes the value of refractive index as a function of radial distance at any fiber diameter.
Refractive index profile
QUESTION The refractive index of the core is uniform and undergoes an abrupt change at the corecladding boundary.
Step-index profile
QUESTION The refractive index at the core varies gradually as a function of radial distance from the fiber center.
Graded-index fiber
QUESTION Determines the shape of the core’s profile.
Profile parameter (α)
QUESTION The NA of a multimode graded-index fiber is at its maximum value at the fiber axis. This NA is the.
Axial numerical aperture,NA(O)