2. 2
Fiber optics uses light to send information
(data).
More formally, fiber optics is the branch
of optical technology concerned with the
transmission of radiant power (light
energy) through fibers.
Light frequencies used in fiber opticLight frequencies used in fiber optic
systems are 100,000 to 400,000 GHz.systems are 100,000 to 400,000 GHz.
Fiber OpticsFiber Optics
3. 3
Brief History of Fiber Optics
In 1880, Alexander Graham BellIn 1880, Alexander Graham Bell
experimented with an apparatus heexperimented with an apparatus he
called a photophone.called a photophone.
The photophone was a deviceThe photophone was a device
constructed from mirrors andconstructed from mirrors and
selenium detectors that transmittedselenium detectors that transmitted
sound waves over a beam of light.sound waves over a beam of light.
4. 4
In 1930, John Logie Baird, anIn 1930, John Logie Baird, an
English scientist and ClarenceEnglish scientist and Clarence
W. Hansell, an AmericanW. Hansell, an American
scientist, was granted patentsscientist, was granted patents
for scanning and transmittingfor scanning and transmitting
television images throughtelevision images through
uncoated cables.uncoated cables.
5. 5
In 1951, Abraham C.S. van Heel ofIn 1951, Abraham C.S. van Heel of
Holland and Harold H. Hopkins andHolland and Harold H. Hopkins and
Narinder S. Kapany of EnglandNarinder S. Kapany of England
experimented with light transmissionexperimented with light transmission
through bundles of fibers. Theirthrough bundles of fibers. Their
studies led to the development ofstudies led to the development of
the flexible fiberscope, which usedthe flexible fiberscope, which used
extensively in the medical field.extensively in the medical field.
6. 6
In 1956, Kapany coinedIn 1956, Kapany coined
the termed “fiber optics”.the termed “fiber optics”.
7. 7
In 1958, Charles H. Townes, anIn 1958, Charles H. Townes, an
American, and Arthur L. Schawlow,American, and Arthur L. Schawlow,
a Canadian, wrote a papera Canadian, wrote a paper
describing how it was possible todescribing how it was possible to
use stimulated emission foruse stimulated emission for
amplifying light waves (laser) asamplifying light waves (laser) as
well as microwaves (maser).well as microwaves (maser).
8. 8
In 1960,In 1960,
Theodore H. Maiman, aTheodore H. Maiman, a
scientist built the firstscientist built the first
optical maser.optical maser.
9. 9
In 1967, Charles K. Kao andIn 1967, Charles K. Kao and
George A. BockhamGeorge A. Bockham
proposed using cladded fiberproposed using cladded fiber
cables.cables.
11. 11
FIBER OPTIC DATA LINKS
To convert an electrical input signal to an
optical signal
To send the optical signal over an optical
fiber
To convert the optical signal back to an
electrical signal
13. 13
Fiber Optic CableFiber Optic Cable
The cable consists of one or more glass fibers,The cable consists of one or more glass fibers,
which act as waveguides for the optical signal.which act as waveguides for the optical signal.
Fiber optic cable is similar to electrical cable inFiber optic cable is similar to electrical cable in
its construction, but provides special protectionits construction, but provides special protection
for the optical fiber within. For systems requiringfor the optical fiber within. For systems requiring
transmission over distances of many kilometers,transmission over distances of many kilometers,
or where two or more fiber optic cables must beor where two or more fiber optic cables must be
joined together, an optical splice is commonlyjoined together, an optical splice is commonly
used.used.
14. 14
The Optical ReceiverThe Optical Receiver
The receiver converts the optical signalThe receiver converts the optical signal
back into a replica of the original electricalback into a replica of the original electrical
signal. The detector of the optical signal issignal. The detector of the optical signal is
either a PIN-type photodiode oreither a PIN-type photodiode or
avalanche-type photodiode.avalanche-type photodiode.
15. 15
The Optical TransmitterThe Optical Transmitter
The transmitter converts an electricalThe transmitter converts an electrical
analog or digital signal into aanalog or digital signal into a
corresponding optical signal. The sourcecorresponding optical signal. The source
of the optical signal can be either a lightof the optical signal can be either a light
emitting diode, or a solid- state laseremitting diode, or a solid- state laser
diode. The most popular wavelengths ofdiode. The most popular wavelengths of
operation for optical transmitters are 850,operation for optical transmitters are 850,
1300, or 1550 nanometers1300, or 1550 nanometers
16. 16
Types of Optical FiberTypes of Optical Fiber
1.1. Plastic core and claddingPlastic core and cladding
2.2. Glass core with plastic cladding (PCS)Glass core with plastic cladding (PCS)
3.3. Glass core and glass cladding (SCS)Glass core and glass cladding (SCS)
17. 17
Modes of PropagationModes of Propagation
Single mode – there is only one path forSingle mode – there is only one path for
light to take down the cablelight to take down the cable
Multimode – if there is more than oneMultimode – if there is more than one
pathpath
Cladding
Cladding
18. 18
Index ProfilesIndex Profiles
Step-index fiberStep-index fiber – it has a central core with a– it has a central core with a
uniform refractive index. The core isuniform refractive index. The core is
surrounded by an outside cladding with asurrounded by an outside cladding with a
uniform refractive index less than that of theuniform refractive index less than that of the
central corecentral core
Grade-index fiberGrade-index fiber – has no cladding, and the– has no cladding, and the
refractive index of the core is nonuniform; it isrefractive index of the core is nonuniform; it is
highest at the center and decreases graduallyhighest at the center and decreases gradually
toward the outer edgetoward the outer edge
A graphical representation of the value of the refractive index across the fiber
19. 19
Optical Fiber ConfigurationOptical Fiber Configuration
1.1. Single-Mode Step-Index FiberSingle-Mode Step-Index Fiber – has a central core that– has a central core that
is sufficiently small so that there is essentially one pathis sufficiently small so that there is essentially one path
that light takes as it propagates down the cablethat light takes as it propagates down the cable
2.2. Multimode Step-Index FiberMultimode Step-Index Fiber – similar to the single-– similar to the single-
mode configuration except that the core is muchmode configuration except that the core is much
larger. This type of fiber has a large light-to-fiberlarger. This type of fiber has a large light-to-fiber
aperture, and consequently, allows more light to enteraperture, and consequently, allows more light to enter
the cable.the cable.
3.3. Multimode Graded-IndexMultimode Graded-Index – it is characterized by a– it is characterized by a
central core that has a refractive index that is non-central core that has a refractive index that is non-
uniform. Light is propagated down this type of fiberuniform. Light is propagated down this type of fiber
through refraction.through refraction.
20. 20
Single-Mode Step-Index FiberSingle-Mode Step-Index Fiber
Advantages:Advantages:
There is minimum dispersion. Because all rays propagating downThere is minimum dispersion. Because all rays propagating down
the fiber take approximately the same path, they take approximatelythe fiber take approximately the same path, they take approximately
the same amount of time to travel down the cable.the same amount of time to travel down the cable.
Because of the high accuracy in reproducing transmitted pulses atBecause of the high accuracy in reproducing transmitted pulses at
the receive end, larger bandwidths and higher informationthe receive end, larger bandwidths and higher information
transmission rates are possible with single- mode step-index fiberstransmission rates are possible with single- mode step-index fibers
than with other types of fiber.than with other types of fiber.
Disadvantages:Disadvantages:
Because the central core is very small, it is difficult to couple lightBecause the central core is very small, it is difficult to couple light
into and out of this type of fiber. The source-to-fiber aperture is theinto and out of this type of fiber. The source-to-fiber aperture is the
smallest of all the fiber types.smallest of all the fiber types.
A highly directive light source such as laser is required.A highly directive light source such as laser is required.
It is expensive and difficult to manufacture.It is expensive and difficult to manufacture.
21. 21
Multimode Step-Index FiberMultimode Step-Index Fiber
Advantages:Advantages:
Inexpensive and easy to manufacture.Inexpensive and easy to manufacture.
It is easy to couple light into and out; they have aIt is easy to couple light into and out; they have a
relatively high large source-to-fiber aperture.relatively high large source-to-fiber aperture.
Disadvantages:Disadvantages:
Light rays take many different paths down the fiber,Light rays take many different paths down the fiber,
which results in large differences in their propagationwhich results in large differences in their propagation
times. Because of this, rays traveling down this type oftimes. Because of this, rays traveling down this type of
fiber have a tendency to spread out.fiber have a tendency to spread out.
The bandwidth and rate of information transfer possibleThe bandwidth and rate of information transfer possible
with this type of cable are less than the other types.with this type of cable are less than the other types.
24. 24
Acceptance Angle & AcceptanceAcceptance Angle & Acceptance
ConeCone
The acceptance angle (or the acceptanceThe acceptance angle (or the acceptance
cone half angle) defines the maximumcone half angle) defines the maximum
angle in which external light rays mayangle in which external light rays may
strike the air/fiber interface and stillstrike the air/fiber interface and still
propagate down the fiber with a responsepropagate down the fiber with a response
that is no greater than 10 dB down fromthat is no greater than 10 dB down from
the peak value. Rotating the acceptancethe peak value. Rotating the acceptance
angle around the fiber axis describes theangle around the fiber axis describes the
acceptance cone of the fiber input.acceptance cone of the fiber input.
26. 26
Numerical ApertureNumerical Aperture
For a step-index fiber: NA = Sin (Acceptance Angle)
And NA =
For a Graded-Index: NA = sin (Critical Angle)
The acceptance angle of a fiber is expressed in
terms of numerical aperture. The numerical aperture
(NA) is defined as the sine of one half of the acceptance
angle of the fiber. It is a figure of merit that is used to
describe the light-gathering or light-collecting ability of
the optical fiber. The larger the magnitude of NA, the
greater the amount of light accepted by the fiber from the
external light source. Typical NA values are 0.1 to 0.4
which correspond to acceptance angles of 11 degrees to
46 degrees. Optical fibers will only transmit light that
enters at an angle that is equal to or less than the
acceptance angle for the particular fiber.
2
2
2
1 nn −
27. 27
Attenuation in Optical FibersAttenuation in Optical Fibers
L = the length of fiber in kilometers
Therefore the unit of attenuation is expressed as dB/km
28. 28
Losses in the Optical FiberLosses in the Optical Fiber
Absorption LossesAbsorption Losses
Material or Rayleigh Scattering LossesMaterial or Rayleigh Scattering Losses
Chromatic or Wavelength DispersionChromatic or Wavelength Dispersion
Radiation LossesRadiation Losses
Modal DispersionModal Dispersion
Coupling LossesCoupling Losses
29. 29
Absorption LossesAbsorption Losses
Absorption loss in an optical fiber is analogousAbsorption loss in an optical fiber is analogous
to power dissipation in copper cables; impuritiesto power dissipation in copper cables; impurities
in the fiber absorb the light and convert it toin the fiber absorb the light and convert it to
heat.heat.
Absorption in optical fibers is explained by three
factors:
Imperfections in the atomic structure of the fiber
material
The intrinsic or basic fiber-material properties
The extrinsic (presence of impurities) fiber-material
properties
30. 30
AbsorptionAbsorption
Essentially, there are three factors thatEssentially, there are three factors that
contribute to the absorption losses incontribute to the absorption losses in
optical fibers:optical fibers:
ultraviolet absorption,ultraviolet absorption,
infrared absorption,infrared absorption,
ion resonance absorption.ion resonance absorption.
31. 31
Ultraviolet AbsorptionUltraviolet Absorption
Is caused by valence electrons in the silicaIs caused by valence electrons in the silica
material from which fibers arematerial from which fibers are
manufactured.manufactured.
Light ionizes the valence electrons intoLight ionizes the valence electrons into
conduction. The ionization is equivalent toconduction. The ionization is equivalent to
a loss in the total light field and,a loss in the total light field and,
consequently contributes to theconsequently contributes to the
transmission losses of the fiber.transmission losses of the fiber.
32. 32
Infrared AbsorptionInfrared Absorption
Is a result of photons of light that areIs a result of photons of light that are
absorbed by the atoms of the glass coreabsorbed by the atoms of the glass core
molecules.molecules.
The absorbed photons are converted toThe absorbed photons are converted to
random mechanical vibrations typical ofrandom mechanical vibrations typical of
heating.heating.
33. 33
Ion Resonance AbsorptionIon Resonance Absorption
Is caused by OH- ions in the material.Is caused by OH- ions in the material.
The source of the OH- ions is waterThe source of the OH- ions is water
molecules that have been trapped in themolecules that have been trapped in the
glass during the manufacturing process.glass during the manufacturing process.
Ion absorption is also caused by iron,Ion absorption is also caused by iron,
copper, and chromium molecules.copper, and chromium molecules.
34. 34
Material or Rayleigh ScatteringMaterial or Rayleigh Scattering
LossesLosses
This type of losses in the fiber is caused byThis type of losses in the fiber is caused by
submicroscopic irregularities developed in thesubmicroscopic irregularities developed in the
fiber during the manufacturing process.fiber during the manufacturing process.
When light rays are propagating down a fiberWhen light rays are propagating down a fiber
strike one of these impurities, they are diffracted.strike one of these impurities, they are diffracted.
Diffraction causes the light to disperse or spreadDiffraction causes the light to disperse or spread
out in many directions. Some of the diffractedout in many directions. Some of the diffracted
light continues down the fiber and some of itlight continues down the fiber and some of it
escapes through the cladding.escapes through the cladding.
The light rays that escape represent a loss inThe light rays that escape represent a loss in
the light power. This is called Rayleigh scatteringthe light power. This is called Rayleigh scattering
loss.loss.
35. 35
Chromatic or WavelengthChromatic or Wavelength
DispersionDispersion
Chromatic dispersion is caused by light sourcesChromatic dispersion is caused by light sources
that emits light spontaneously such as the LED.that emits light spontaneously such as the LED.
Each wavelength within the composite lightEach wavelength within the composite light
signal travels at a different velocity. Thussignal travels at a different velocity. Thus
arriving at the receiver end at different times.arriving at the receiver end at different times.
This results in a distorted signal; the distortion isThis results in a distorted signal; the distortion is
calledcalled chromatic distortionchromatic distortion..
Chromatic distortion can be eliminated by usingChromatic distortion can be eliminated by using
monochromatic light sources such as themonochromatic light sources such as the
injection laser diode (ILD).injection laser diode (ILD).
36. 36
Radiation LossesRadiation Losses
Radiation losses are caused by small bends andRadiation losses are caused by small bends and
kinks in the fiber.kinks in the fiber.
Essentially, there are two types of bends:Essentially, there are two types of bends:
Microbends and constant-radius bends.Microbends and constant-radius bends.
MicrobendingMicrobending occurs as a result of differences in the thermaloccurs as a result of differences in the thermal
contraction rates between the core and cladding material. Acontraction rates between the core and cladding material. A
microbend represents a discontinuity in the fiber wheremicrobend represents a discontinuity in the fiber where
Rayleigh scattering can occur.Rayleigh scattering can occur.
Constant-radius bendsConstant-radius bends occur where fibers are bentoccur where fibers are bent
during handling or installation.during handling or installation.
37. 37
Modal DispersionModal Dispersion
Modal dispersion orModal dispersion or pulse spreadingpulse spreading isis
caused by the difference in thecaused by the difference in the
propagation times of light rays that takepropagation times of light rays that take
different paths down a fiber.different paths down a fiber.
Obviously, modal dispersion can occurObviously, modal dispersion can occur
only in multimode fibers. It can be reducedonly in multimode fibers. It can be reduced
considerably by using graded-index fibersconsiderably by using graded-index fibers
and almost entirely eliminated by single-and almost entirely eliminated by single-
mode step-index fibers.mode step-index fibers.
38. 38
Coupling LossesCoupling Losses
Coupling losses can occur in any of theCoupling losses can occur in any of the
following three types of optical junctions:following three types of optical junctions:
light source-to-fiber connections, fiber-to-light source-to-fiber connections, fiber-to-
fiber connections, and fiber-to-fiber connections, and fiber-to-
photodetector connections. Junctionphotodetector connections. Junction
losses are most often caused by one oflosses are most often caused by one of
the following alignment problems: lateralthe following alignment problems: lateral
misalignment, gap misalignment, angularmisalignment, gap misalignment, angular
misalignment, and imperfect surfacemisalignment, and imperfect surface
finishes.finishes.
41. 41
Light SourcesLight Sources
There are two devices commonly used toThere are two devices commonly used to
generate light for fiber opticgenerate light for fiber optic
communications systems: light-emittingcommunications systems: light-emitting
diodes (LEDs) and injection laser diodesdiodes (LEDs) and injection laser diodes
(ILDs). Both devices have advantages and(ILDs). Both devices have advantages and
disadvantages and the selection of onedisadvantages and the selection of one
device over the other is determined bydevice over the other is determined by
system economic and performancesystem economic and performance
requirements.requirements.
42. 42
Light-Emitting Diode (LED)Light-Emitting Diode (LED)
Simply a P-N junction diodeSimply a P-N junction diode
Made from a semiconductor material suchMade from a semiconductor material such
as aluminum-gallium arsenide (AlGaAs) oras aluminum-gallium arsenide (AlGaAs) or
gallium-arsenide-phosphide (GaAsP)gallium-arsenide-phosphide (GaAsP)
Emits light by spontaneous emission: lightEmits light by spontaneous emission: light
is emitted as a result of the recombinationis emitted as a result of the recombination
of electrons and holesof electrons and holes
43. 43
Light-Emitting Diode (LED)Light-Emitting Diode (LED)
The simplest LED structures are homojunction,The simplest LED structures are homojunction,
epitaxially grown, or single-diffused devices.epitaxially grown, or single-diffused devices.
Epitaxially grown LEDsEpitaxially grown LEDs are generallyare generally
constructed of silicon-doped gallium arsenide. Aconstructed of silicon-doped gallium arsenide. A
typical wavelength of light emitted is 940 nm,typical wavelength of light emitted is 940 nm,
and a typical output power is approximately 3and a typical output power is approximately 3
mW at 100 mA of forward current.mW at 100 mA of forward current.
Planar diffused (homojunction) LEDsPlanar diffused (homojunction) LEDs outputoutput
approximately 500 microwatts at a wavelength ofapproximately 500 microwatts at a wavelength of
900 nm.900 nm.
44. 44
Light-Emitting Diode (LED)Light-Emitting Diode (LED)
The primary disadvantage of homojunction LEDsThe primary disadvantage of homojunction LEDs
is the nondirectionality of their light emission,is the nondirectionality of their light emission,
which makes them a poor choice as a lightwhich makes them a poor choice as a light
source for fiber optic systems.source for fiber optic systems.
The planar heterojunction LED is quite similar toThe planar heterojunction LED is quite similar to
the epitaxially grown LED except that thethe epitaxially grown LED except that the
geometry is designed such that the forwardgeometry is designed such that the forward
current is concentrated to a very small area ofcurrent is concentrated to a very small area of
the active layer.the active layer.
45. 45
Light-Emitting Diode (LED)Light-Emitting Diode (LED)
Advantages of heterojunction LED over theAdvantages of heterojunction LED over the
homojunction type:homojunction type:
The increase in current density generates aThe increase in current density generates a
more brilliant light spot.more brilliant light spot.
The smaller emitting area makes it easier toThe smaller emitting area makes it easier to
couple its emitted light into a fiber.couple its emitted light into a fiber.
The small effective area has a smallerThe small effective area has a smaller
capacitance, which allows the planarcapacitance, which allows the planar
heterojunction LED to be used at higher speeds.heterojunction LED to be used at higher speeds.
47. 47
The Burrus etched-well LEDThe Burrus etched-well LED
For the more practical applicationFor the more practical application
such as telecommunications, datasuch as telecommunications, data
rates in excess of 100 Mbps arerates in excess of 100 Mbps are
required. The Burrus etched-wellrequired. The Burrus etched-well
LED emits light in many directions.LED emits light in many directions.
The etched well helps concentrateThe etched well helps concentrate
the emitted light to a very smallthe emitted light to a very small
area. These devices are morearea. These devices are more
efficient than the standard surfaceefficient than the standard surface
emitters and they allow more poweremitters and they allow more power
to be coupled into the optical fiber,to be coupled into the optical fiber,
but they are also more difficult tobut they are also more difficult to
manufacture and more expensive.manufacture and more expensive.
Emitted light rays
48. 48
Edge-Emitting DiodeEdge-Emitting Diode
These LEDs emit a more directional lightThese LEDs emit a more directional light
pattern than do the surface-emitting LEDs.pattern than do the surface-emitting LEDs.
The light is emitted from an active stripeThe light is emitted from an active stripe
and forms an elliptical beam. Surface-and forms an elliptical beam. Surface-
emitting LEDs are more commonly usedemitting LEDs are more commonly used
than edge emitters because they emitthan edge emitters because they emit
more light. However, the coupling lossesmore light. However, the coupling losses
with surface emitters are greater and theywith surface emitters are greater and they
have narrower bandwidths.have narrower bandwidths.
49. 49
Injection Laser Diode (ILD)Injection Laser Diode (ILD)
Advantages of ILDs:Advantages of ILDs:
Because ILDs have a more direct radiation pattern, it isBecause ILDs have a more direct radiation pattern, it is
easier to couple their light into an optical fiber. Thiseasier to couple their light into an optical fiber. This
reduces the coupling losses and allows smaller fibers toreduces the coupling losses and allows smaller fibers to
be used.be used.
The radiant output power from an ILD is greater than thatThe radiant output power from an ILD is greater than that
for an LED. A typical output power for an ILD is 5 mW (7for an LED. A typical output power for an ILD is 5 mW (7
dBm) and 0.5 mW (-3 dBm) for LEDs. This allows ILDsdBm) and 0.5 mW (-3 dBm) for LEDs. This allows ILDs
to provide a higher drive power and to be used forto provide a higher drive power and to be used for
systems that operate over longer distances.systems that operate over longer distances.
ILDs can be used at higher bit rates than can LEDs.ILDs can be used at higher bit rates than can LEDs.
ILDs generate monochromatic light, which reducesILDs generate monochromatic light, which reduces
chromatic or wavelength dispersion.chromatic or wavelength dispersion.
50. 50
Injection Laser Diode (ILD)Injection Laser Diode (ILD)
Disadvantages of ILDs:Disadvantages of ILDs:
ILDs are typically on the order of 10 timesILDs are typically on the order of 10 times
more expensive than LEDs.more expensive than LEDs.
Because ILDs operate at higher powers,Because ILDs operate at higher powers,
they typically have a much shorter lifetimethey typically have a much shorter lifetime
than LEDs.than LEDs.
ILDs are more temperature dependentILDs are more temperature dependent
than LEDs.than LEDs.
51. 51
Light DetectorsLight Detectors
There are two devices that are commonlyThere are two devices that are commonly
used to detect light energy in fiber opticused to detect light energy in fiber optic
communications receivers: PIN (p-type-communications receivers: PIN (p-type-
intrinsic-n-type) diodes and APDintrinsic-n-type) diodes and APD
(avalanche photodiodes).(avalanche photodiodes).
54. 54
Basic Cable DesignBasic Cable Design
The two basic cable designs are theThe two basic cable designs are the
loose-tube cable and tight-buffered cableloose-tube cable and tight-buffered cable
( either a single fiber or a multi-fiber).( either a single fiber or a multi-fiber).
Loose-tube cable, used in the majority ofLoose-tube cable, used in the majority of
outside-plant installations in Northoutside-plant installations in North
America, and tight-buffered cable,America, and tight-buffered cable,
primarily used inside buildings.primarily used inside buildings.
55. 55
Basic Cable DesignBasic Cable Design
The modular design of loose-tube cablesThe modular design of loose-tube cables
typically holds up to 12 fibers per buffer tubetypically holds up to 12 fibers per buffer tube
with a maximum per cable fiber count of morewith a maximum per cable fiber count of more
than 200 fibers. Loose-tube cables can be all-than 200 fibers. Loose-tube cables can be all-
dielectric or optionally armored. The modulardielectric or optionally armored. The modular
buffer-tube design permits easy drop-off ofbuffer-tube design permits easy drop-off of
groups of fibers at intermediate points, withoutgroups of fibers at intermediate points, without
interfering with other protected buffer tubesinterfering with other protected buffer tubes
being routed to other locations. The loose-tubebeing routed to other locations. The loose-tube
design also helps in the identification anddesign also helps in the identification and
administration of fibers in the system.administration of fibers in the system.
56. 56
Basic Cable DesignBasic Cable Design
Single-fiber tight-buffered cables are usedSingle-fiber tight-buffered cables are used
as pigtails, patch cords and jumpers toas pigtails, patch cords and jumpers to
terminate loose-tube cables directly intoterminate loose-tube cables directly into
optoelectronics transmitters, receivers andoptoelectronics transmitters, receivers and
other active and passive components.other active and passive components.
Multi-fiber tight-buffered cables also areMulti-fiber tight-buffered cables also are
available and are used primarily foravailable and are used primarily for
alternative routing and handling flexibilityalternative routing and handling flexibility
and ease within buildings.and ease within buildings.
57. 57
Loose-Tube CableLoose-Tube Cable
In a loose-tube cable design, color-coded plastic buffer tubes houseIn a loose-tube cable design, color-coded plastic buffer tubes house
and protect optical fibers. A gel filling compound impedes waterand protect optical fibers. A gel filling compound impedes water
penetration. Excess fiber length (relative to buffer tube length)penetration. Excess fiber length (relative to buffer tube length)
insulates fibers from stresses of installation and environmentalinsulates fibers from stresses of installation and environmental
loading. Buffer tubes are stranded around a dielectric or steelloading. Buffer tubes are stranded around a dielectric or steel
central member, which serves as an anti-buckling element.central member, which serves as an anti-buckling element.
The cable core, typically surrounded by aramid yarn, is the primaryThe cable core, typically surrounded by aramid yarn, is the primary
tensile strength member. The outer polyethylene jacket is extrudedtensile strength member. The outer polyethylene jacket is extruded
over the core. If armoring is required, a corrugated steel tape isover the core. If armoring is required, a corrugated steel tape is
formed around a single jacketed cable with an additional jacketformed around a single jacketed cable with an additional jacket
extruded over the armor. Coated FiberOuter JacketSteel Tapeextruded over the armor. Coated FiberOuter JacketSteel Tape
Armor Inner Jacket Aramid Strength MemberBinderInterstitialArmor Inner Jacket Aramid Strength MemberBinderInterstitial
FillingCentral MemberFillingCentral Member
(Steel Wire or Dielectric) Interstitial FillingLoose Tube Cable(Steel Wire or Dielectric) Interstitial FillingLoose Tube Cable
Loose-tube cables typically are used for outside-plant installation inLoose-tube cables typically are used for outside-plant installation in
aerial, duct and direct-buried applications.aerial, duct and direct-buried applications.
58. 58
Loose Tube CableLoose Tube Cable
Coated Fiber
Outer Jacket
Steel Tape Armor
Inner Jacket
Aramid Strength Member
Binder
Interstitial Filling
Central Member
(Steel Wire or Dielectric)
Interstitial Filling
Loose Tube Cable
59. 59
Tight-Buffered CableTight-Buffered Cable
With tight-buffered cable designs, the buffering materialWith tight-buffered cable designs, the buffering material
is in direct contact with the fiber. This design is suited foris in direct contact with the fiber. This design is suited for
"jumper cables" which connect outside plant cables to"jumper cables" which connect outside plant cables to
terminal equipment, and also for linking various devicesterminal equipment, and also for linking various devices
in a premises network.in a premises network.
Multi-fiber, tight-buffered cables often are used for intra-Multi-fiber, tight-buffered cables often are used for intra-
building, risers, general building and plenumbuilding, risers, general building and plenum
applications.applications.
The tight-buffered design provides a rugged cableThe tight-buffered design provides a rugged cable
structure to protect individual fibers during handling,structure to protect individual fibers during handling,
routing and cable connection. Yarn strength membersrouting and cable connection. Yarn strength members
keep the tensile load away from the fiber.keep the tensile load away from the fiber.
As with loose-tube cables, optical specifications for tight-As with loose-tube cables, optical specifications for tight-
buffered cables also should include the maximumbuffered cables also should include the maximum
performance of all fibers over the operating temperatureperformance of all fibers over the operating temperature
range and life of the cable. Averages should not berange and life of the cable. Averages should not be
acceptable.acceptable.
60. 60
Tight-Buffered CableTight-Buffered Cable
Glass Fiber
Thermoplastic
Overcoating or
Buffer
PVC Jacket (Non-Plenum)
or Fluoride Co-Polymer
Jacket (Plenum)
Fiber Coating
Aramid Strength
Member
Tight-buffered Cable
61. 61
Optical Fiber ConnectorsOptical Fiber Connectors
Optical connectors are the means by which fiber opticOptical connectors are the means by which fiber optic
cable is usually connected to peripheral equipment andcable is usually connected to peripheral equipment and
to other fibers. These connectors are similar to theirto other fibers. These connectors are similar to their
electrical counterparts in function and outwardelectrical counterparts in function and outward
appearance but are actually high precision devices. Inappearance but are actually high precision devices. In
operation, the connector centers the small fiber so thatoperation, the connector centers the small fiber so that
its light gathering core lies directly over and in line withits light gathering core lies directly over and in line with
the light source (or other fiber) to tolerances of a few tenthe light source (or other fiber) to tolerances of a few ten
thousandths of an inch. Since the core size of commonthousandths of an inch. Since the core size of common
50 micron fiber is only 0.002 inches, the need for such50 micron fiber is only 0.002 inches, the need for such
extreme tolerances is obvious.extreme tolerances is obvious.
There are many different types of optical connectors inThere are many different types of optical connectors in
use today. The SMA connector, which was firstuse today. The SMA connector, which was first
developed before the invention of single-mode fiber, wasdeveloped before the invention of single-mode fiber, was
the most popular type of connector until recently.the most popular type of connector until recently.
63. 63
Optical SplicesOptical Splices
While optical connectors can be used to connect fiber optic cablesWhile optical connectors can be used to connect fiber optic cables
together, there are other methods that result in much lower losstogether, there are other methods that result in much lower loss
splices. Two of the most common and popular are the mechanicalsplices. Two of the most common and popular are the mechanical
splice and the fusion splice. Both are capable of splice losses in thesplice and the fusion splice. Both are capable of splice losses in the
range of 0.15 dB (3%) to 0.1 dB (2%).range of 0.15 dB (3%) to 0.1 dB (2%).
In a mechanical splice, the ends of two pieces of fiber areIn a mechanical splice, the ends of two pieces of fiber are
cleaned and stripped, then carefully butted together and alignedcleaned and stripped, then carefully butted together and aligned
using a mechanical assembly. A gel is used at the point of contactusing a mechanical assembly. A gel is used at the point of contact
to reduce light reflection and keep the splice loss at a minimum. Theto reduce light reflection and keep the splice loss at a minimum. The
ends of the fiber are held together by friction or compression, andends of the fiber are held together by friction or compression, and
the splice assembly features a locking mechanism so that the fibersthe splice assembly features a locking mechanism so that the fibers
remained aligned.remained aligned.
A fusion splice, by contrast, involves actually melting (fusing)A fusion splice, by contrast, involves actually melting (fusing)
together the ends of two pieces of fiber. The result is a continuoustogether the ends of two pieces of fiber. The result is a continuous
fiber without a break. Fusion splices require special expensivefiber without a break. Fusion splices require special expensive
splicing equipment but can be performed very quickly, so the costsplicing equipment but can be performed very quickly, so the cost
becomes reasonable if done in quantity. As fusion splices arebecomes reasonable if done in quantity. As fusion splices are
fragile, mechanical devices are usually employed to protect them.fragile, mechanical devices are usually employed to protect them.
64. 64
Designing Optical Fiber SystemsDesigning Optical Fiber Systems
The following step-by-step procedure should be followed whenThe following step-by-step procedure should be followed when
designing any system.designing any system.
Determine the correct optical transmitter and receiver combinationDetermine the correct optical transmitter and receiver combination
based upon the signal to be transmitted (Analog, Digital, Audio,based upon the signal to be transmitted (Analog, Digital, Audio,
Video, RS-232, RS-422, RS-485, etc.).Video, RS-232, RS-422, RS-485, etc.).
Determine the operating power available (AC, DC, etc.).Determine the operating power available (AC, DC, etc.).
Determine the special modifications (if any) necessaryDetermine the special modifications (if any) necessary
(Impedances, Bandwidths, Special Connectors, Special Fiber Size,(Impedances, Bandwidths, Special Connectors, Special Fiber Size,
etc.).etc.).
Calculate the total optical loss (in dB) in the system by adding theCalculate the total optical loss (in dB) in the system by adding the
cable loss, splice loss, and connector loss. These parameterscable loss, splice loss, and connector loss. These parameters
should be available from the manufacturer of the electronics andshould be available from the manufacturer of the electronics and
fiber.fiber.
Compare the loss figure obtained with the allowable optical lossCompare the loss figure obtained with the allowable optical loss
budget of the receiver. Be certain to add a safety margin factor of atbudget of the receiver. Be certain to add a safety margin factor of at
least 3 dB to the entire system.least 3 dB to the entire system.
Check that the fiber bandwidth is adequate to pass the signalCheck that the fiber bandwidth is adequate to pass the signal
desired.desired.
66. 66
Breakout CableBreakout Cable
Breakout cables are designed with all-dielectricBreakout cables are designed with all-dielectric
construction to insure EMI immunity.construction to insure EMI immunity.
These cables are obtainable in a wide range ofThese cables are obtainable in a wide range of
fiber counts and can be used for routing withinfiber counts and can be used for routing within
buildings, in riser shafts, and under computerbuildings, in riser shafts, and under computer
room floors.room floors.
The Breakout design enables the individualThe Breakout design enables the individual
routing, or "fanning", of individual fibers forrouting, or "fanning", of individual fibers for
termination and maintenance.termination and maintenance.
In addition to the standard duty 2.4 mm subunitIn addition to the standard duty 2.4 mm subunit
design, a 2.9 mm heavy duty and a 2.0 mm lightdesign, a 2.9 mm heavy duty and a 2.0 mm light
duty design are also available.duty design are also available.
67. 67
Interconnect CableInterconnect Cable
Cable for interconnecting equipment is available inCable for interconnecting equipment is available in
single-mode and multimode fiber sizes and its allsingle-mode and multimode fiber sizes and its all
dielectric construction provides EMI immunity .dielectric construction provides EMI immunity .
Available in one- and two-fiber designs, these cablesAvailable in one- and two-fiber designs, these cables
are optimized for ease of connectorization and use asare optimized for ease of connectorization and use as
"jumpers" for intra-building distribution."jumpers" for intra-building distribution.
Its small diameter and bend radius provide easyIts small diameter and bend radius provide easy
installation in constrained areas.installation in constrained areas.
This cable can be ordered for plenum or riserThis cable can be ordered for plenum or riser
environments. Products include single fiber cable, two-environments. Products include single fiber cable, two-
fiber Zipcord, and two-fiber DIB Cable.fiber Zipcord, and two-fiber DIB Cable.
Uncabled fiber, coated only with a thermoplastic buffer,Uncabled fiber, coated only with a thermoplastic buffer,
is also available for pigtail applications with insideis also available for pigtail applications with inside
equipment.equipment.
68. 68
Loose Tube CableLoose Tube Cable
Loose tube cables are for general purposeLoose tube cables are for general purpose
outdoor use.outdoor use.
The loose tube design provides stable andThe loose tube design provides stable and
highly reliable transmission parameters for ahighly reliable transmission parameters for a
variety of applications.variety of applications.
The design also permits significantThe design also permits significant
improvements in the density of fibers containedimprovements in the density of fibers contained
in a given cable diameter while allowing flexibilityin a given cable diameter while allowing flexibility
to suit many system designs.to suit many system designs.
These cables are suitable for outdoor duct,These cables are suitable for outdoor duct,
aerial, and direct buried installations, and foraerial, and direct buried installations, and for
indoor use when installed in accordance withindoor use when installed in accordance with
NEC Article 770.NEC Article 770.
69. 69
FeaturesFeatures
Different fiber types available within a cableDifferent fiber types available within a cable
(hybrid construction).(hybrid construction).
Lowest losses at long distances, for use in ductLowest losses at long distances, for use in duct
aerial, and direct buried applications.aerial, and direct buried applications.
Wide range of fiber counts (up to 216).Wide range of fiber counts (up to 216).
Available with single--mode and multimode fiberAvailable with single--mode and multimode fiber
types.types.
All dielectric or steel central member.All dielectric or steel central member.
Loose Tube Cable is also available with armoredLoose Tube Cable is also available with armored
construction for added protection.construction for added protection.
70. 70
Low Smoke – Zero Halogen CableLow Smoke – Zero Halogen Cable
Halex-RTM is a low smoke, zero halogen fiberHalex-RTM is a low smoke, zero halogen fiber
optic cable, designed to replace standardoptic cable, designed to replace standard
polyethylene jacketed fiber optic cables inpolyethylene jacketed fiber optic cables in
environments where public safety is of greatenvironments where public safety is of great
concern.concern.
In addition to having low smoke properties,In addition to having low smoke properties,
Halex-R cable meets the NEC requirements forHalex-R cable meets the NEC requirements for
risers, passes all U.S. flame requirements for ULrisers, passes all U.S. flame requirements for UL
1666 and UL 1581, and is OFNR listed up to 1561666 and UL 1581, and is OFNR listed up to 156
fibers.fibers.
71. 71
LXE Light Guide Express EntryLXE Light Guide Express Entry
CableCable
The LXE (Lightguide Express Entry) sheath system isThe LXE (Lightguide Express Entry) sheath system is
designed with the loop distribution market in mind, wheredesigned with the loop distribution market in mind, where
express entry (accessing fibers in the middle of a cableexpress entry (accessing fibers in the middle of a cable
span) is a common practice.span) is a common practice.
The LXE sheath system achieves a 600 pound (2670 N)The LXE sheath system achieves a 600 pound (2670 N)
tensile rating through the use of linearly applied strengthtensile rating through the use of linearly applied strength
members placed 180 degrees opposite each other.members placed 180 degrees opposite each other.
High density polyethylene (HDPE) is used for the cableHigh density polyethylene (HDPE) is used for the cable
jacket to provide both faster installation, through a lowerjacket to provide both faster installation, through a lower
coefficient of friction, and optimum cable core protectioncoefficient of friction, and optimum cable core protection
in hostile environments.in hostile environments.
72. 72
FeaturesFeatures
Strength members in cable sheath (not inStrength members in cable sheath (not in
cable core).cable core).
Non-metallic cable core.Non-metallic cable core.
73. 73
Light Pack CableLight Pack Cable
Lightpack Cable consists of fiber "bundles" heldLightpack Cable consists of fiber "bundles" held
together with color coded yarn binders.together with color coded yarn binders.
Cable can hold up to 144 fibers and still maintainCable can hold up to 144 fibers and still maintain
a large clearance in the core tube.a large clearance in the core tube.
A water-blocking compound, specificallyA water-blocking compound, specifically
designed for LIGHTPACK Cable, adds extradesigned for LIGHTPACK Cable, adds extra
flexibility, protects the fiber and virtuallyflexibility, protects the fiber and virtually
eliminates microbending losses.eliminates microbending losses.
Lightpack cable is compact size, rugged design,Lightpack cable is compact size, rugged design,
contains a high density polyethylene sheath andcontains a high density polyethylene sheath and
has a high strength-to-weight ratio.has a high strength-to-weight ratio.
74. 74
Indoor/Outdoor Loose Tube CableIndoor/Outdoor Loose Tube Cable
The RLT Series of loose tube fiber optic cables isThe RLT Series of loose tube fiber optic cables is
designed for installation both outdoors and indoors indesigned for installation both outdoors and indoors in
areas required by the (NEC) to be riser rated Typeareas required by the (NEC) to be riser rated Type
OFNR. They meet or exceed Article 770 of the NEC andOFNR. They meet or exceed Article 770 of the NEC and
UL Subject 1666 (Type OFNR). They also meet CSAUL Subject 1666 (Type OFNR). They also meet CSA
C22.2 No. 232-M1988 Type OFN-FT4.C22.2 No. 232-M1988 Type OFN-FT4.
All of the RLT products utilize a proprietary ChromaTek 3All of the RLT products utilize a proprietary ChromaTek 3
jacketing system that is designed for resistance tojacketing system that is designed for resistance to
moisture, sunlight and flame for use both indoors andmoisture, sunlight and flame for use both indoors and
outdoors. These cables are loose tube, gel-filledoutdoors. These cables are loose tube, gel-filled
constructions for excellent resistance to moisture. Theyconstructions for excellent resistance to moisture. They
are available with single--mode or multimode fibers withare available with single--mode or multimode fibers with
up to a maximum of 72 fibers.up to a maximum of 72 fibers.
75. 75
Indoor/Outdoor Loose Tube CableIndoor/Outdoor Loose Tube Cable
Because these outdoor cables are riser rated, theyBecause these outdoor cables are riser rated, they
eliminate the need for a separate point of demarcation,eliminate the need for a separate point of demarcation,
i.e., splicing to a riser rated cable within 50 feet of thei.e., splicing to a riser rated cable within 50 feet of the
point where the outdoor cable enters the building aspoint where the outdoor cable enters the building as
required by the NEC. These cables may be run throughrequired by the NEC. These cables may be run through
risers directly to a convenient network hub or splicingrisers directly to a convenient network hub or splicing
closet for interconnection to the electro-optical hardwarecloset for interconnection to the electro-optical hardware
or other horizontal distribution cables as desired.or other horizontal distribution cables as desired.
No extra splice or termination hardware is required at theNo extra splice or termination hardware is required at the
entrance to the facility, and cable management is madeentrance to the facility, and cable management is made
easier by the use of just one cable. This installation easeeasier by the use of just one cable. This installation ease
is especially useful in Campus type installations whereis especially useful in Campus type installations where
buildings are interconnected with outdoor fiber opticbuildings are interconnected with outdoor fiber optic
cables.cables.
76. 76
Tactical/Military CableTactical/Military Cable
Tactical cable utilizes a tight buffer configurationTactical cable utilizes a tight buffer configuration
in an all dielectric construction.in an all dielectric construction.
The tight buffer design offers increasedThe tight buffer design offers increased
ruggedness, ease of handling andruggedness, ease of handling and
connectorization.connectorization.
The absence of metallic components decreasesThe absence of metallic components decreases
the possibility of detection and minimizes systemthe possibility of detection and minimizes system
problems associated with electromagneticproblems associated with electromagnetic
interference.interference.
77. 77
FeaturesFeatures
Proven compatibility with existingProven compatibility with existing
ruggedized connectors.ruggedized connectors.
Lightweight and flexible: no anti--bucklingLightweight and flexible: no anti--buckling
elements required.elements required.
Available in connectorized cableAvailable in connectorized cable
assemblies.assemblies.
Available with 50, 62.5 and 100 micronAvailable with 50, 62.5 and 100 micron
multimode fibers, as well as single--modemultimode fibers, as well as single--mode
and radiation--hardened fibers.and radiation--hardened fibers.
78. 78
TEMPEST Cable DescriptionTEMPEST Cable Description
For use where secure communications are a majorFor use where secure communications are a major
consideration, and Tempest requirements must be met.consideration, and Tempest requirements must be met.
The Tempest rated cable is available in a variety of cableThe Tempest rated cable is available in a variety of cable
constructions.constructions.
Tempest relates to government requirements forTempest relates to government requirements for
shielding communications equipment and environments.shielding communications equipment and environments.
One common application is the use of fiber optic cable inOne common application is the use of fiber optic cable in
conjunction with RF shielded enclosures. Theseconjunction with RF shielded enclosures. These
enclosures have been specially constructed to suppressenclosures have been specially constructed to suppress
the emission of RF signals, and must meet the Transientthe emission of RF signals, and must meet the Transient
Electro-magnet, Pulse Emanation Standard (TEMPEST).Electro-magnet, Pulse Emanation Standard (TEMPEST).
79. 79
Cont.Cont.
For a system to be TEMPEST qualified, it mustFor a system to be TEMPEST qualified, it must
be tested in accordance with MIL-STD-285, andbe tested in accordance with MIL-STD-285, and
it must also meet the requirements stated init must also meet the requirements stated in
NSA 65-6. All elements of the system,NSA 65-6. All elements of the system,
individually and combined, must meet theindividually and combined, must meet the
TEMPEST standard.TEMPEST standard.
In the case of fiber optics, the "system" consistsIn the case of fiber optics, the "system" consists
of the cable (which is dielectric and non-of the cable (which is dielectric and non-
conductive), and the tube through which theconductive), and the tube through which the
cable passes.cable passes.
