11

Optical Fiber Optical Fiber CommunicationsCommunications

22

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 optic Light frequencies used in fiber optic systems are 100,000 to 400,000 GHz. systems are 100,000 to 400,000 GHz.

Fiber OpticsFiber Optics

33

Brief History of Fiber Optics In 1880, Alexander Graham Bell In 1880, Alexander Graham Bell

experimented with an apparatus he called a experimented with an apparatus he called a photophone. photophone.

The photophone was a device constructed The photophone was a device constructed from mirrors and selenium detectors that from mirrors and selenium detectors that transmitted sound waves over a beam of transmitted sound waves over a beam of light.light.

44

In 1930, John Logie Baird, an In 1930, John Logie Baird, an English scientist and Clarence English scientist and Clarence

W. Hansell, an American W. Hansell, an American scientist, was granted patents scientist, was granted patents for scanning and transmitting for scanning and transmitting

television images through television images through uncoated cables.uncoated cables.

55

In 1951, Abraham C.S. van Heel of In 1951, Abraham C.S. van Heel of Holland and Harold H. Hopkins and Holland and Harold H. Hopkins and

Narinder S. Kapany of England Narinder S. Kapany of England experimented with light transmission experimented with light transmission

through bundles of fibers. Their through bundles of fibers. Their studies led to the development of studies led to the development of

the flexible fiberscope, which used the flexible fiberscope, which used extensively in the medical field.extensively in the medical field.

66

In 1956, Kapany coined In 1956, Kapany coined the termed “fiber optics”.the termed “fiber optics”.

77

In 1958, Charles H. Townes, an In 1958, Charles H. Townes, an American, and Arthur L. Schawlow, American, and Arthur L. Schawlow,

a Canadian, wrote a paper a Canadian, wrote a paper describing how it was possible to describing how it was possible to

use stimulated emission for use stimulated emission for amplifying light waves (laser) as amplifying light waves (laser) as

well as microwaves (maser).well as microwaves (maser).

88

In 1960, In 1960, Theodore H. Maiman, a Theodore H. Maiman, a

scientist built the first scientist built the first optical maser.optical maser.

99

In 1967, Charles K. Kao and In 1967, Charles K. Kao and George A. Bockham George A. Bockham

proposed using cladded fiber proposed using cladded fiber cables.cables.

1010

1111

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

1212

A/D Interface

Voltage-to-current

Converter

LightSource

Source-to-fiber interface

Fiber-to-light

detector interface

LightDetector

Current-to-current

converter

A/DInterface

Input

Output

Optical Transmitter

Optical Receiver

Optical Fiber

Fiber Optic Data LinkFiber Optic Data Link

1313

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 in Fiber optic cable is similar to electrical cable in its construction, but provides special protection its construction, but provides special protection for the optical fiber within. For systems requiring for 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 be or where two or more fiber optic cables must be joined together, an optical splice is commonly joined together, an optical splice is commonly used. used.

1414

The Optical ReceiverThe Optical Receiver

The receiver converts the optical signal The receiver converts the optical signal back into a replica of the original electrical back into a replica of the original electrical signal. The detector of the optical signal is signal. The detector of the optical signal is either a PIN-type photodiode or either a PIN-type photodiode or avalanche-type photodiode. avalanche-type photodiode.

1515

The Optical TransmitterThe Optical Transmitter

The transmitter converts an electrical The transmitter converts an electrical analog or digital signal into a analog or digital signal into a corresponding optical signal. The source corresponding optical signal. The source of the optical signal can be either a light of the optical signal can be either a light emitting diode, or a solid- state laser emitting diode, or a solid- state laser diode. The most popular wavelengths of diode. The most popular wavelengths of operation for optical transmitters are 850, operation for optical transmitters are 850, 1300, or 1550 nanometers1300, or 1550 nanometers

1616

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)

1717

Modes of PropagationModes of Propagation

Single mode – there is only one path for Single mode – there is only one path for light to take down the cablelight to take down the cable

Multimode – if there is more than one Multimode – if there is more than one pathpath

Cladding

Cladding

1818

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 is uniform refractive index. The core is surrounded by an outside cladding with a surrounded by an outside cladding with a uniform refractive index less than that of the uniform 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 is refractive index of the core is nonuniform; it is highest at the center and decreases gradually highest at the center and decreases gradually toward the outer edge toward the outer edge

A graphical representation of the value of the refractive index across the fiber

1919

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 path is 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 Fiber Multimode Step-Index Fiber – similar to the single-– similar to the single-mode configuration except that the core is much mode configuration except that the core is much larger. This type of fiber has a large light-to-fiber larger. This type of fiber has a large light-to-fiber aperture, and consequently, allows more light to enter aperture, 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 fiber uniform. Light is propagated down this type of fiber through refraction. through refraction.

2020

Single-Mode Step-Index FiberSingle-Mode Step-Index Fiber

Advantages: Advantages: There is minimum dispersion. Because all rays propagating down There is minimum dispersion. Because all rays propagating down

the fiber take approximately the same path, they take approximately the 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 at Because of the high accuracy in reproducing transmitted pulses at the receive end, larger bandwidths and higher information the receive end, larger bandwidths and higher information transmission rates are possible with single- mode step-index fibers transmission 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 light Because 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 the into 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.

2121

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 a It 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 propagation which results in large differences in their propagation times. Because of this, rays traveling down this type of times. 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 possible The 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.

2222

Index ProfileSingle Mode Step Index

Multimode Step Index

Multimode Graded Index

2323

2424

Acceptance Angle & Acceptance Acceptance Angle & Acceptance ConeCone

The acceptance angle (or the acceptance The acceptance angle (or the acceptance cone half angle) defines the maximum cone half angle) defines the maximum angle in which external light rays may angle in which external light rays may strike the air/fiber interface and still strike the air/fiber interface and still propagate down the fiber with a response propagate down the fiber with a response that is no greater than 10 dB down from that is no greater than 10 dB down from the peak value. Rotating the acceptance the peak value. Rotating the acceptance angle around the fiber axis describes the angle around the fiber axis describes the acceptance cone of the fiber input.acceptance cone of the fiber input.

2525

Maximum Acceptance Angle =

AcceptanceCone

Optical Fiber

AcceptanceAngle

2626

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.

2727

Attenuation in Optical FibersAttenuation in Optical Fibers

L = the length of fiber in kilometersTherefore the unit of attenuation is expressed as dB/km

2828

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

2929

Absorption LossesAbsorption Losses

Absorption loss in an optical fiber is analogous Absorption loss in an optical fiber is analogous to power dissipation in copper cables; impurities to power dissipation in copper cables; impurities in the fiber absorb the light and convert it to in 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

3030

AbsorptionAbsorption

Essentially, there are three factors that Essentially, there are three factors that contribute to the absorption losses in contribute to the absorption losses in optical fibers: optical fibers: ultraviolet absorption, ultraviolet absorption, infrared absorption, infrared absorption, ion resonance absorption.ion resonance absorption.

3131

Ultraviolet AbsorptionUltraviolet Absorption

Is caused by valence electrons in the silica Is caused by valence electrons in the silica material from which fibers are material from which fibers are manufactured. manufactured.

Light ionizes the valence electrons into Light ionizes the valence electrons into conduction. The ionization is equivalent to conduction. The ionization is equivalent to a loss in the total light field and, a loss in the total light field and, consequently contributes to the consequently contributes to the transmission losses of the fiber.transmission losses of the fiber.

3232

Infrared AbsorptionInfrared Absorption

Is a result of photons of light that are Is a result of photons of light that are absorbed by the atoms of the glass core absorbed by the atoms of the glass core molecules. molecules.

The absorbed photons are converted to The absorbed photons are converted to random mechanical vibrations typical of random mechanical vibrations typical of heating.heating.

3333

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 water The source of the OH- ions is water

molecules that have been trapped in the molecules 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.

3434

Material or Rayleigh Scattering Material or Rayleigh Scattering LossesLosses

This type of losses in the fiber is caused by This type of losses in the fiber is caused by submicroscopic irregularities developed in the submicroscopic irregularities developed in the fiber during the manufacturing process. fiber during the manufacturing process.

When light rays are propagating down a fiber When 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 spread Diffraction causes the light to disperse or spread out in many directions. Some of the diffracted out in many directions. Some of the diffracted light continues down the fiber and some of it light continues down the fiber and some of it escapes through the cladding. escapes through the cladding.

The light rays that escape represent a loss in The light rays that escape represent a loss in the light power. This is called Rayleigh scattering the light power. This is called Rayleigh scattering loss.loss.

3535

Chromatic or Wavelength Chromatic or Wavelength DispersionDispersion

Chromatic dispersion is caused by light sources Chromatic 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 light Each wavelength within the composite light signal travels at a different velocity. Thus signal 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 is This results in a distorted signal; the distortion is called called chromatic distortionchromatic distortion. .

Chromatic distortion can be eliminated by using Chromatic distortion can be eliminated by using monochromatic light sources such as the monochromatic light sources such as the injection laser diode (ILD).injection laser diode (ILD).

3636

Radiation LossesRadiation Losses

Radiation losses are caused by small bends and Radiation 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 thermal occurs as a result of differences in the thermal contraction rates between the core and cladding material. A contraction rates between the core and cladding material. A microbend represents a discontinuity in the fiber where microbend represents a discontinuity in the fiber where Rayleigh scattering can occur. Rayleigh scattering can occur.

Constant-radius bendsConstant-radius bends occur where fibers are bent occur where fibers are bent during handling or installation. during handling or installation.

3737

Modal DispersionModal Dispersion

Modal dispersion or Modal dispersion or pulse spreadingpulse spreading is is caused by the difference in the caused by the difference in the propagation times of light rays that take propagation times of light rays that take different paths down a fiber.different paths down a fiber.

Obviously, modal dispersion can occur Obviously, modal dispersion can occur only in multimode fibers. It can be reduced only in multimode fibers. It can be reduced considerably by using graded-index fibers considerably 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.

3838

Coupling LossesCoupling Losses

Coupling losses can occur in any of the Coupling 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. Junction photodetector connections. Junction losses are most often caused by one of losses are most often caused by one of the following alignment problems: lateral the following alignment problems: lateral misalignment, gap misalignment, angular misalignment, gap misalignment, angular misalignment, and imperfect surface misalignment, and imperfect surface finishes.finishes.

3939

Coupling LossesCoupling Losses

Axial displacement

Gap displacement

Angular displacement

Surface Finish

Loss

Loss

Loss

Loss

4040

4141

Light SourcesLight Sources

There are two devices commonly used to There are two devices commonly used to generate light for fiber optic generate light for fiber optic communications systems: light-emitting communications systems: light-emitting diodes (LEDs) and injection laser diodes diodes (LEDs) and injection laser diodes (ILDs). Both devices have advantages and (ILDs). Both devices have advantages and disadvantages and the selection of one disadvantages and the selection of one device over the other is determined by device over the other is determined by system economic and performance system economic and performance requirements.requirements.

4242

Light-Emitting Diode (LED)Light-Emitting Diode (LED)

Simply a P-N junction diodeSimply a P-N junction diode Made from a semiconductor material such Made from a semiconductor material such

as aluminum-gallium arsenide (AlGaAs) or as aluminum-gallium arsenide (AlGaAs) or gallium-arsenide-phosphide (GaAsP)gallium-arsenide-phosphide (GaAsP)

Emits light by spontaneous emission: light Emits light by spontaneous emission: light is emitted as a result of the recombination is emitted as a result of the recombination of electrons and holesof electrons and holes

4343

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 generally are generally constructed of silicon-doped gallium arsenide. A constructed 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 3 and 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 output output approximately 500 microwatts at a wavelength of approximately 500 microwatts at a wavelength of 900 nm. 900 nm.

4444

Light-Emitting Diode (LED)Light-Emitting Diode (LED)

The primary disadvantage of homojunction LEDs The 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 light which 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 to The planar heterojunction LED is quite similar to the epitaxially grown LED except that the the epitaxially grown LED except that the geometry is designed such that the forward geometry is designed such that the forward current is concentrated to a very small area of current is concentrated to a very small area of the active layer.the active layer.

4545

Light-Emitting Diode (LED)Light-Emitting Diode (LED)

Advantages of heterojunction LED over the Advantages of heterojunction LED over the homojunction type:homojunction type:

The increase in current density generates a The increase in current density generates a more brilliant light spot.more brilliant light spot.

The smaller emitting area makes it easier to The 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 smaller The small effective area has a smaller capacitance, which allows the planar capacitance, which allows the planar heterojunction LED to be used at higher speeds.heterojunction LED to be used at higher speeds.

4646

Light-Emitting Diode (LED)Light-Emitting Diode (LED)

Light Emission

n-type substrate

n-epitaxial layer

p-epitaxial layer

Homojunction LED structure: silicon-doped-

gallium arsenide

Planar heterojunction LED

4747

The Burrus etched-well LEDThe Burrus etched-well LED

For the more practical application For the more practical application such as telecommunications, data such as telecommunications, data rates in excess of 100 Mbps are rates in excess of 100 Mbps are required. The Burrus etched-well required. The Burrus etched-well LED emits light in many directions. LED emits light in many directions. The etched well helps concentrate The etched well helps concentrate the emitted light to a very small the emitted light to a very small area. These devices are more area. These devices are more efficient than the standard surface efficient than the standard surface emitters and they allow more power emitters 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 to but they are also more difficult to manufacture and more expensive.manufacture and more expensive.

Emitted light rays

4848

Edge-Emitting DiodeEdge-Emitting Diode

These LEDs emit a more directional light These 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 stripe The light is emitted from an active stripe and forms an elliptical beam. Surface-and forms an elliptical beam. Surface-emitting LEDs are more commonly used emitting LEDs are more commonly used than edge emitters because they emit than edge emitters because they emit more light. However, the coupling losses more light. However, the coupling losses with surface emitters are greater and they with surface emitters are greater and they have narrower bandwidths.have narrower bandwidths.

4949

Injection Laser Diode (ILD)Injection Laser Diode (ILD)

Advantages of ILDs:Advantages of ILDs: Because ILDs have a more direct radiation pattern, it is Because ILDs have a more direct radiation pattern, it is

easier to couple their light into an optical fiber. This easier to couple their light into an optical fiber. This reduces the coupling losses and allows smaller fibers to reduces the coupling losses and allows smaller fibers to be used.be used.

The radiant output power from an ILD is greater than that The radiant output power from an ILD is greater than that for an LED. A typical output power for an ILD is 5 mW (7 for an LED. A typical output power for an ILD is 5 mW (7 dBm) and 0.5 mW (-3 dBm) for LEDs. This allows ILDs dBm) and 0.5 mW (-3 dBm) for LEDs. This allows ILDs to provide a higher drive power and to be used for to 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 reduces ILDs generate monochromatic light, which reduces

chromatic or wavelength dispersion.chromatic or wavelength dispersion.

5050

Injection Laser Diode (ILD)Injection Laser Diode (ILD)

Disadvantages of ILDs:Disadvantages of ILDs: ILDs are typically on the order of 10 times ILDs 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 lifetime they typically have a much shorter lifetime than LEDs.than LEDs.

ILDs are more temperature dependent ILDs are more temperature dependent than LEDs.than LEDs.

5151

Light DetectorsLight Detectors

There are two devices that are commonly There are two devices that are commonly used to detect light energy in fiber optic used to detect light energy in fiber optic communications receivers: PIN (p-type-communications receivers: PIN (p-type-intrinsic-n-type) diodes and APD intrinsic-n-type) diodes and APD (avalanche photodiodes).(avalanche photodiodes).

5252

PIN DiodePIN Diode

AssignmentAssignment

5353

Avalanche PhotodiodeAvalanche Photodiode

AssignmentAssignment

5454

Basic Cable DesignBasic Cable Design

The two basic cable designs are the loose-The two basic cable designs are the loose-tube cable and tight-buffered cable 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 of Loose-tube cable, used in the majority of

outside-plant installations in North outside-plant installations in North America, and tight-buffered cable, America, and tight-buffered cable, primarily used inside buildings. primarily used inside buildings.

5555

Basic Cable DesignBasic Cable Design

The modular design of loose-tube cables The modular design of loose-tube cables typically holds up to 12 fibers per buffer tube typically holds up to 12 fibers per buffer tube with a maximum per cable fiber count of more with 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 modular dielectric or optionally armored. The modular buffer-tube design permits easy drop-off of buffer-tube design permits easy drop-off of groups of fibers at intermediate points, without groups of fibers at intermediate points, without interfering with other protected buffer tubes interfering with other protected buffer tubes being routed to other locations. The loose-tube being routed to other locations. The loose-tube design also helps in the identification and design also helps in the identification and administration of fibers in the system. administration of fibers in the system.

5656

Basic Cable DesignBasic Cable Design

Single-fiber tight-buffered cables are used Single-fiber tight-buffered cables are used as pigtails, patch cords and jumpers to as pigtails, patch cords and jumpers to terminate loose-tube cables directly into terminate loose-tube cables directly into optoelectronics transmitters, receivers and optoelectronics transmitters, receivers and other active and passive components. other active and passive components.

Multi-fiber tight-buffered cables also are Multi-fiber tight-buffered cables also are available and are used primarily for available and are used primarily for alternative routing and handling flexibility alternative routing and handling flexibility and ease within buildings. and ease within buildings.

5757

Loose-Tube CableLoose-Tube Cable In a loose-tube cable design, color-coded plastic buffer tubes house In a loose-tube cable design, color-coded plastic buffer tubes house

and protect optical fibers. A gel filling compound impedes water and 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 environmental insulates fibers from stresses of installation and environmental loading. Buffer tubes are stranded around a dielectric or steel loading. 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 primary The cable core, typically surrounded by aramid yarn, is the primary tensile strength member. The outer polyethylene jacket is extruded tensile strength member. The outer polyethylene jacket is extruded over the core. If armoring is required, a corrugated steel tape is over the core. If armoring is required, a corrugated steel tape is formed around a single jacketed cable with an additional jacket formed around a single jacketed cable with an additional jacket extruded over the armor. Coated FiberOuter JacketSteel Tape extruded over the armor. Coated FiberOuter JacketSteel Tape Armor Inner Jacket Aramid Strength MemberBinderInterstitial Armor Inner Jacket Aramid Strength MemberBinderInterstitial FillingCentral Member FillingCentral 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 in Loose-tube cables typically are used for outside-plant installation in

aerial, duct and direct-buried applications. aerial, duct and direct-buried applications.

5858

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

5959

Tight-Buffered CableTight-Buffered Cable With tight-buffered cable designs, the buffering material is With tight-buffered cable designs, the buffering material is

in direct contact with the fiber. This design is suited for 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 devices terminal 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 plenum applications. building, risers, general building and plenum applications.

The tight-buffered design provides a rugged cable The 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 members routing 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 maximum buffered cables also should include the maximum performance of all fibers over the operating temperature performance of all fibers over the operating temperature range and life of the cable. Averages should not be range and life of the cable. Averages should not be acceptable. acceptable.

6060

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

6161

Optical Fiber ConnectorsOptical Fiber Connectors Optical connectors are the means by which fiber optic Optical connectors are the means by which fiber optic

cable is usually connected to peripheral equipment and cable is usually connected to peripheral equipment and to other fibers. These connectors are similar to their to other fibers. These connectors are similar to their electrical counterparts in function and outward electrical counterparts in function and outward appearance but are actually high precision devices. In appearance but are actually high precision devices. In operation, the connector centers the small fiber so that operation, the connector centers the small fiber so that its light gathering core lies directly over and in line with its light gathering core lies directly over and in line with the light source (or other fiber) to tolerances of a few ten the light source (or other fiber) to tolerances of a few ten thousandths of an inch. Since the core size of common thousandths of an inch. Since the core size of common 50 micron fiber is only 0.002 inches, the need for such 50 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 in There are many different types of optical connectors in use today. The SMA connector, which was first use today. The SMA connector, which was first developed before the invention of single-mode fiber, was developed before the invention of single-mode fiber, was the most popular type of connector until recently. the most popular type of connector until recently.

6262

Fiber ConnectorsFiber Connectors

6363

Optical SplicesOptical Splices While optical connectors can be used to connect fiber optic cables While optical connectors can be used to connect fiber optic cables

together, there are other methods that result in much lower loss together, there are other methods that result in much lower loss splices. Two of the most common and popular are the mechanical splices. Two of the most common and popular are the mechanical splice and the fusion splice. Both are capable of splice losses in the splice 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 are In a mechanical splice, the ends of two pieces of fiber are cleaned and stripped, then carefully butted together and aligned cleaned and stripped, then carefully butted together and aligned using a mechanical assembly. A gel is used at the point of contact using a mechanical assembly. A gel is used at the point of contact to reduce light reflection and keep the splice loss at a minimum. The to reduce light reflection and keep the splice loss at a minimum. The ends of the fiber are held together by friction or compression, and ends of the fiber are held together by friction or compression, and the splice assembly features a locking mechanism so that the fibers the splice assembly features a locking mechanism so that the fibers remained aligned. remained aligned.

A fusion splice, by contrast, involves actually melting A fusion splice, by contrast, involves actually melting (fusing) together the ends of two pieces of fiber. The result is a (fusing) together the ends of two pieces of fiber. The result is a continuous fiber without a break. Fusion splices require special continuous fiber without a break. Fusion splices require special expensive splicing equipment but can be performed very quickly, so expensive splicing equipment but can be performed very quickly, so the cost becomes reasonable if done in quantity. As fusion splices the cost becomes reasonable if done in quantity. As fusion splices are fragile, mechanical devices are usually employed to protect are fragile, mechanical devices are usually employed to protect them. them.

6464

Designing Optical Fiber SystemsDesigning Optical Fiber Systems

The following step-by-step procedure should be followed when designing The following step-by-step procedure should be followed when designing any system. any system.

Determine the correct optical transmitter and receiver combination Determine 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) necessary (Impedances, Determine the special modifications (if any) necessary (Impedances,

Bandwidths, Special Connectors, Special Fiber Size, etc.). Bandwidths, Special Connectors, Special Fiber Size, etc.). Calculate the total optical loss (in dB) in the system by adding the Calculate the total optical loss (in dB) in the system by adding the

cable loss, splice loss, and connector loss. These parameters should cable loss, splice loss, and connector loss. These parameters should be available from the manufacturer of the electronics and fiber. be available from the manufacturer of the electronics and fiber.

Compare the loss figure obtained with the allowable optical loss Compare the loss figure obtained with the allowable optical loss budget of the receiver. Be certain to add a safety margin factor of at budget 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 signal desired. Check that the fiber bandwidth is adequate to pass the signal desired.

6565

BASIC TYPES OF OPTICAL BASIC TYPES OF OPTICAL FIBER CABLEFIBER CABLE

1.1. Breakout CableBreakout Cable2.2. Interconnect CableInterconnect Cable3.3. Loose Tube CableLoose Tube Cable4.4. Low Smoke – Zero Halogen CableLow Smoke – Zero Halogen Cable5.5. LXE Light Guide Express Entry CableLXE Light Guide Express Entry Cable6.6. Light Pack CableLight Pack Cable7.7. Indoor/Outdoor Loose Tube CableIndoor/Outdoor Loose Tube Cable8.8. Tactical/Military Cable Tactical/Military Cable 9.9. TEMPEST Cable DescriptionTEMPEST Cable Description

6666

Breakout CableBreakout Cable

Breakout cables are designed with all dielectric Breakout cables are designed with all dielectric construction to insure EMI immunity. construction to insure EMI immunity.

These cables are obtainable in a wide range of These cables are obtainable in a wide range of fiber counts and can be used for routing within fiber counts and can be used for routing within buildings, in riser shafts, and under computer buildings, in riser shafts, and under computer room floors. room floors.

The Breakout design enables the individual The Breakout design enables the individual routing, or "fanning", of individual fibers for routing, or "fanning", of individual fibers for termination and maintenance. termination and maintenance.

In addition to the standard duty 2.4 mm subunit In addition to the standard duty 2.4 mm subunit design, a 2.9 mm heavy duty and a 2.0 mm light design, a 2.9 mm heavy duty and a 2.0 mm light duty design are also available. duty design are also available.

6767

Interconnect CableInterconnect Cable Cable for interconnecting equipment is available in Cable for interconnecting equipment is available in

single-mode and multimode fiber sizes and its all single-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 cables Available in one- and two-fiber designs, these cables are optimized for ease of connectorization and use as are 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 easy Its small diameter and bend radius provide easy installation in constrained areas. installation in constrained areas.

This cable can be ordered for plenum or riser This 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 inside is also available for pigtail applications with inside equipment. equipment.

6868

Loose Tube CableLoose Tube Cable Loose tube cables are for general purpose outdoor Loose tube cables are for general purpose outdoor

use. use. The loose tube design provides stable and highly The loose tube design provides stable and highly

reliable transmission parameters for a variety of reliable transmission parameters for a variety of applications. applications.

The design also permits significant improvements in The design also permits significant improvements in the density of fibers contained in a given cable the density of fibers contained in a given cable diameter while allowing flexibility to suit many system diameter while allowing flexibility to suit many system designs. designs.

These cables are suitable for outdoor duct, aerial, These cables are suitable for outdoor duct, aerial, and direct buried installations, and for indoor use and direct buried installations, and for indoor use when installed in accordance with NEC Article 770. when installed in accordance with NEC Article 770.

6969

FeaturesFeatures

Different fiber types available within a cable Different fiber types available within a cable (hybrid construction). (hybrid construction).

Lowest losses at long distances, for use in duct Lowest 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 fiber Available 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 armored Loose Tube Cable is also available with armored

construction for added protection. construction for added protection.

7070

Low Smoke – Zero Halogen CableLow Smoke – Zero Halogen Cable

Halex RTM is a low smoke, zero halogen fiber Halex RTM is a low smoke, zero halogen fiber optic cable, designed to replace standard optic cable, designed to replace standard polyethylene jacketed fiber optic cables in polyethylene jacketed fiber optic cables in environments where public safety is of great environments 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 for Halex R cable meets the NEC requirements for risers, passes all U.S. flame requirements for UL risers, passes all U.S. flame requirements for UL 1666 and UL 1581, and is OFNR listed up to 156 1666 and UL 1581, and is OFNR listed up to 156 fibers. fibers.

7171

LXE Light Guide Express Entry LXE Light Guide Express Entry CableCable

The LXE (Lightguide Express Entry) sheath system is The LXE (Lightguide Express Entry) sheath system is designed with the loop distribution market in mind, where designed with the loop distribution market in mind, where express entry (accessing fibers in the middle of a cable express 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 strength tensile 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 cable High density polyethylene (HDPE) is used for the cable jacket to provide both faster installation, through a lower jacket to provide both faster installation, through a lower coefficient of friction, and optimum cable core protection coefficient of friction, and optimum cable core protection in hostile environments. in hostile environments.

7272

FeaturesFeatures

Strength members in cable sheath (not in Strength members in cable sheath (not in cable core). cable core).

Non metallic cable core.Non metallic cable core.

7373

Light Pack CableLight Pack Cable

Lightpack Cable consists of fiber "bundles" held Lightpack 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 maintain Cable 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, specifically A water blocking compound, specifically designed for LIGHTPACK Cable, adds extra designed for LIGHTPACK Cable, adds extra flexibility, protects the fiber and virtually flexibility, 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 and contains a high density polyethylene sheath and has a high strength to weight ratio. has a high strength to weight ratio.

7474

Indoor/Outdoor Loose Tube CableIndoor/Outdoor Loose Tube Cable

The RLT Series of loose tube fiber optic cables is The RLT Series of loose tube fiber optic cables is designed for installation both outdoors and indoors in designed for installation both outdoors and indoors in areas required by the (NEC) to be riser rated Type areas required by the (NEC) to be riser rated Type OFNR. They meet or exceed Article 770 of the NEC and OFNR. They meet or exceed Article 770 of the NEC and UL Subject 1666 (Type OFNR). They also meet CSA UL 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 3 All of the RLT products utilize a proprietary ChromaTek 3 jacketing system that is designed for resistance to jacketing system that is designed for resistance to moisture, sunlight and flame for use both indoors and moisture, sunlight and flame for use both indoors and outdoors. These cables are loose tube, gel filled outdoors. These cables are loose tube, gel filled constructions for excellent resistance to moisture. They constructions for excellent resistance to moisture. They are available with single- mode or multimode fibers with are available with single- mode or multimode fibers with up to a maximum of 72 fibers. up to a maximum of 72 fibers.

7575

Indoor/Outdoor Loose Tube CableIndoor/Outdoor Loose Tube Cable

Because these outdoor cables are riser rated, they Because 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 the i.e., splicing to a riser rated cable within 50 feet of the point where the outdoor cable enters the building as point where the outdoor cable enters the building as required by the NEC. These cables may be run through required by the NEC. These cables may be run through risers directly to a convenient network hub or splicing risers directly to a convenient network hub or splicing closet for interconnection to the electro-optical hardware closet 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 the No extra splice or termination hardware is required at the entrance to the facility, and cable management is made entrance to the facility, and cable management is made easier by the use of just one cable. This installation ease easier by the use of just one cable. This installation ease is especially useful in Campus type installations where is especially useful in Campus type installations where buildings are interconnected with outdoor fiber optic buildings are interconnected with outdoor fiber optic cables. cables.

7676

Tactical/Military CableTactical/Military Cable

Tactical cable utilizes a tight buffer configuration Tactical cable utilizes a tight buffer configuration in an all dielectric construction. in an all dielectric construction.

The tight buffer design offers increased The tight buffer design offers increased ruggedness, ease of handling and ruggedness, ease of handling and connectorization.connectorization.

The absence of metallic components decreases The absence of metallic components decreases the possibility of detection and minimizes system the possibility of detection and minimizes system problems associated with electromagnetic problems associated with electromagnetic interference. interference.

7777

FeaturesFeatures

Proven compatibility with existing Proven compatibility with existing ruggedized connectors. ruggedized connectors.

Lightweight and flexible: no anti- buckling Lightweight and flexible: no anti- buckling elements required. elements required.

Available in connectorized cable Available in connectorized cable assemblies. assemblies.

Available with 50, 62.5 and 100 micron Available with 50, 62.5 and 100 micron multimode fibers, as well as single -mode multimode fibers, as well as single -mode and radiation- hardened fibers. and radiation- hardened fibers.

7878

TEMPEST Cable DescriptionTEMPEST Cable Description

For use where secure communications are a major For 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 cable The Tempest rated cable is available in a variety of cable constructions. constructions.

Tempest relates to government requirements for Tempest 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 in One common application is the use of fiber optic cable in conjunction with RF shielded enclosures. These conjunction with RF shielded enclosures. These enclosures have been specially constructed to suppress enclosures have been specially constructed to suppress the emission of RF signals, and must meet the Transient the emission of RF signals, and must meet the Transient Electro-magnet, Pulse Emanation Standard (TEMPEST). Electro-magnet, Pulse Emanation Standard (TEMPEST).

7979

Cont.Cont.

For a system to be TEMPEST qualified, it must For a system to be TEMPEST qualified, it must be tested in accordance with MIL-STD 285, and it be tested in accordance with MIL-STD 285, and it must also meet the requirements stated in NSA must also meet the requirements stated in NSA 65 6. All elements of the system, individually and 65 6. All elements of the system, individually and combined, must meet the TEMPEST standard. combined, must meet the TEMPEST standard.

In the case of fiber optics, the "system" consists In 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 the conductive), and the tube through which the cable passes.cable passes.