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`Optical Communication ONT
`Prof. Dr.-Ing. G. Wenke
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`Report
`On
`Fiber Optic Cables
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`Due date: 18/12/2015
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`Name
`Rishabh Chikker
`
`Navaneetha C M
`
`Aditya Ghosh
`
`Bartyr Barakov
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`Matriculation No
`5006237
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`Signature
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`
`5006274
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`5006239
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`5006230
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`1 | P a g e
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`US Conec EX1013
`IPR2024-00115
`U.S. Patent No. 11,307,369
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`

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`CONTENTS
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`1. INTRODUCTION_____________________________________ 1
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`2. CATEGORIES OF CABLING __________________________ 7
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`3. MULTI FIBER BREAKOUT CABLE ____________________ 13
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`4. HYBRID CABLES________________________________ 18
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`5. SUBMARINE CABLES_________________________________22
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`6. REFERENCES________________________________________28
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`Fiber Optic Cables
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`1. Introduction
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`What is Fiber Optic Cable?
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`Cabling is the process of packaging optical fibers in a cable structure for handling and
`protection. In some applications bare fibers work just fine, such as fiber optic sensors
`and laboratory use. However for most communication applications fibers must be
`packaged in a cable for practical use. The major benefits of fiber optic cabling are:
`
` Easy Handling
`Some communication systems require tens or even hundreds of fibers (such as a
`metro backbone system). Put fibers in a cable make it very easy to install and
`maintain.
` Protection from damaging forces
`Fiber optic cables have to be pulled into place through ducts (outdoor) or
`conduits (indoor). Pulling eyes are attached to the strength members or cable
`outer jackets. This is critical for isolating the fibers from the applied pulling
`forces. Glass fibers cannot endure more than 0.1% to 0.2% elongation during
`installation.
` Protection from harsh environment factors
`Cable structures protect fibers from moisture (outdoor cables), extreme
`temperature (aerial cables) and influx of hydrogen into the fiber (which causes
`light absorption peak at 1380nm which in turn impair fibers’ transmission
`properties).
`
`Fiber Optic Cable Based on Fiber Types
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`Based upon fiber types in a cable, fiber optic cables can be categorized as three types.
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`Single Mode Fiber Optic Cable
`All fibers in the cable are single mode fibers.
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`Multimode Fiber Optic Cable - Multi Mode Fiber Optic Cable
`All fibers in the cable are multimode cables.
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`Hybrid/Composite Cable
`Both single mode and multimode fibers are packaged in one cable, such as 4 multimode
`fibers and 4 single mode fibers in a single cable.
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`Elements in a Fiber Optic Cables
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`The construction design and choices of materials are vital in determining characteristics
`of a cable. The design factors for some types of fiber optic cables are listed below.
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`Indoor cables
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`Fire safety is the number one factor in selecting indoor cables, particularly those that
`run through plenum spaces. Indoor cables must pass the flame-retardant and smoke-
`inhibitor ratings specified by NEC.
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`Outdoor cables
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`Moisture resistance and temperature tolerance are the major factors when choosing
`materials for outdoor environment cables. They also need to be ultraviolet (UV)
`resistant.
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`Cable Jacket Materials
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`Polyethylene (PE)
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`PE (black color) is the standard jacket material for outdoor fiber optic cables. PE has
`excellent moisture – and weather-resistance properties. It has very stable dielectric
`properties over a wide temperature range. It is also abrasion-resistant.
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`Polyvinyl Chloride (PVC)
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`PVC is the most common material for indoor cables; however it can also be used for
`outdoor cables. It is flexible and fire-retardant. PVC is more expensive than PE.
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`Polyvinyl difluoride (PVDF)
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`PVDF is used for plenum cables because it has better fire-retardant properties than PE
`and produces little smoke.
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`Low Smoke Zero Halogen (LSZH) plastics
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`LSZH plastics are used for a special kind of cable called LSZH cables. They produce
`little smoke and no toxic halogen compounds. But they are the most expensive jacket
`material.
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`Aramid Yarn
`Aramid yarn is a yellow color, fiber looking material. It is strong and is used to bundle
`and protect the loose tubes or fibers in the cable. It is the strength member to provide
`tensile strength along the length of the cable during and after installation. When a cable
`is pulled into a duct, the tension is applied to the aramid yarn instead of the fibers.
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`Central Strength Member
`Many fiber optic cables has a central strength member, made of steel, fiberglass or
`aramid yarn. Central strength members are needed to provide the rigidity to keep the
`cable from buckling. Central strength members are common in outdoor cables and some
`high fiber counts indoor cables.
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`Gel Compound
`Gel compound fills buffer tubes and cable interiors, making the cable impervious to
`water. It needs to be completely cleaned off when the cable end is stripped for
`termination.
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`Ripcord
`Ripcord is a thin but very strong thread embedded just below the cable jacket. Its role is
`to split the cable easily without harming cable interiors.
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`
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`Two Basic Fiber Structures
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`Fiber optic cable are available in a wide variety of physical constructions. Fiber cables
`can be anything from simple simplex or duplex (zipcord) cables used for jumpers to
`144-fiber cable for intercity transmission.
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`However most of the fibers used in these cables come down to two basic configurations
`– 900µm tight buffered fibers or 250 µm coated fibers (also called bare fibers). Actually
`tight buffered fibers cover a coated fiber(the coating is soft plastic) with a thick layer of
`harder plastic, making it easier to handle and providing physical protection.
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`Figure1.1: Difference between Tight Buffered Fiber and Coated Fiber
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`The structure of a 250µm coated fiber (bare fiber)
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` Core (9µm for standard single mode fibers, 50µm or 62.5µm for multimode
`fibers)
` Cladding (125µm)
` Coating (soft plastic, 250µm is the most popular, sometimes 400µm is also used)
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`The structure of a 900µm tight buffered fiber
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` Core (9µm for standard single mode fibers, 50µm or 62.5µm for multimode
`fibers)
` Cladding (125µm)
` Coating (soft plastic, 250µm)
` Tight buffer (hard plastic, 900µm)
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`Figure 1.2: 250µm and 900µm tight buffered fiber
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`Fiber Optic Cable Construction - Two Basic Types
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`Based on 900µm tight buffered fiber and 250µm coated fiber there are two basic types
`of fiber optic cable constructions – Tight Buffered Cable and Loose Tube Cable.
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`Tight Buffered Cable
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`Multiple color coded 900um tight buffered fibers can be packed tightly together in a
`compact cable structure, an approach widely used indoors, these cables are called tight
`buffered cables. Tight buffered cables are used to connect outside plant cables to
`terminal equipment, and also for linking various devices in a premises network.
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`Multi-fiber, tight buffered cables often are used for intra-building, risers, general
`building and plenum applications. Tight buffered cables are mostly built for indoor
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`applications, although some tight buffered cables have been built for outdoor
`applications too.
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`Figure 1.3: Tight Buffered Fiber Optic Cable Sample
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`Structure of a Tight Buffered Cable
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`Elements in a tight buffered fiber optic cable
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`1. Multiple 900µm tight buffered fibers (stranded around the central
`strength member)
`2. Central strength member (in the center of the cable)
`3. Aramid Yarn (wrapped around the fibers, for physical protection and
`cable pulling)
`4. Ripcord (for easy removal of outer jacket)
`5. Outer jacket (also called sheath, PVC is most common for indoor cables
`because of its flexible, fire-retardant and easy extrusion characteristics. )
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`Figure 1.4:Cross Section of a Tight Buffered Fiber Optic Cable
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`Loose Tube Cable
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`On the other hand multiple (up to 12) 250µm coated fibers (bare fibers) can be
`put inside a color coded, flexible plastic tube, which usually is filled with a gel
`compound that prevents moisture from seeping through the hollow tube. Buffer tubes
`are stranded around a dielectric or steel central member. Aramid yarn are used as
`primary strength member. Then an outer polyethylene jacket is extruded over the core.
`These cables are called loose tube cables.
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`Loose tube structure isolates the fibers from the cable structure. This is a big advantage
`in handling thermal and other stresses encountered outdoors, which is why most loose
`tube fiber optic cables are built for outdoor applications.
`Loose-tube cables typically are used for outside-plant installation in aerial, duct and
`direct-buried applications.
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`Figure 1.5: Fiber Optic Loose Tube Cable Samples
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`Structure of a Loose Tube Cable
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`Elements in a loose tube fiber optic cable:
`
`1. Multiple 250 µm coated bare fibers (in loose tube)
`2. One or more loose tubes holding 250 µm bare fibers. Loose tubes strand
`around the central strength member.
`3. Moisture blocking gel in each loose tube for water blocking and
`protection of 250 µm fibers
`4. Central strength member (in the center of the cable and is stranded
`around by loose tubes)
`5. Aramid Yarn as strength member
`6. Ripcord (for easy removal of outer jacket)
`7. Outer jacket (Polyethylene is most common for outdoor cables because
`of its moisture resistant, abrasion resistant and stable over wide
`temperature range characteristics. )
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`Figure 1.6: Cross Section of a Loose Tube Fiber Optic Cable
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`2. Categories of Cabling
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`Fiber-optic cables may be categorized by the type of installation environment, on the
`number of individual fibers and according to the application. There can be three main
`categories of cable
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`1. Indoor Cables
`2. Outdoor Cables
`3. Indoor/Outdoor
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`They can consist of one (simplex), two (duplex) or more (multifiber) individual fibers.
`Simplex cables provide one-way transmission, while duplex cables allow transmission
`in both direction. Multifiber cables may carry many fiber pairs surrounding a central
`strength member, as shown in the Figure: 2-1; or they may take the form of ribbon
`cables, which are individual cables in a row surrounded by a single jacket Figure: 2-2
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` Figure: 2-1
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`Figure: 2-2
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`1
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`– James N. Downing: Fiber Optic Communications, 2005, ISNB: 1-4018-6635-2
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`Indoor Cables
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`Elaborating the indoor optical cables they have a diverse variety of applications inside a
`building. They are replacing outdoor cables because the indoor cables have more
`flexibility, cheaper and convenience to use inside a building. Indoor cables have some
`characteristics that allow it to be more favorable. Such as:
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` No need grounding and lightning protection - Since they are free of metal
` Easy to strip - They are 900µm TBII tight buffered fibers
` All information of the cable can be printed on the outer sheath.
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`In addition, letter-coding designation according to German standardization
`institutes of DIN & VDE (as shown in Table 1.1, page 9)
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`It is also designed to withstand temperature ups/downs, and to stand against mechanical
`stresses that the cable might face inside the building. These characters are present while
`it still has its similar optical transmission as the outdoor cables. This would lead to
`lower increase in attenuation with the splice joints. Indoor cables are placed in an
`optical fiber distribution closure inside the buildings. The distribution of the cables
`could be more flexible to manage and process. Figure: 2-3 shows a verity of indoor
`cables.
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`Simplex Round Indoor Cable
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`Duplex Zipcord Indoor Cable
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`Multi-fiber Distribution Indoor Cable
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`Figure: 2-3: Variety of indoor cables
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`Codes
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`Fiber-optics cables, coding according to DIN VDE 0888
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`Table 1.1 2
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`2
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`– Twentsche Kabel Deutschland
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`Color Coding
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`It would seems that the color coding, the color of the jackets and buffers means the
`characteristics (Fire retardant, Mechanical, Single or Multi mode, Dielectric properties
`of the sheath…) of the cable. But not all manufacturers adhere to the same standards.
`The color coding, the difference of the color is used to identify the cables, to visual
`recognize each of them to connect in right order. Table: 1.1 shows the difference of
`used colors for cables 1-12 fiber strands. In case of more fibers they are indicated with
`same colors, but with lines or dotted lines.
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`Figure: 2-4: Color Coding
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`General requirements
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`The most important requirements of isolation of the indoor fiber-optic cables:
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` Cables must not be supportive and flame retardant and have low smoke and
`halogen;
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` Cables must have a small bending radius;
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` Cables must be effectively armored;
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`Types of indoor cables
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`There are three types of indoor fiber optic cables:
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`1.1 Interconnect cables
`1.2 Break-out cables (Fan-out)
`1.3 Multi-indoor cables (MIC)
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`Interconnect Cables
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`Interconnect cables are used to connect the devices, the blocks in the device, process
`controls, wired office systems to transmit data, image, video, and voice in intra-building
`distribution. They can one or two fiber designed (Simplex Round, Duplex Zipcord,
`Duplex Round).
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`Figure: 2-5
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`These cables suffer almost minimal mechanical loading. For compounds of the blocks
`in the device is often sufficient optical fibers in buffer coating. If there is frequently
`switching of interconnect cables for connections, it may contain coils of protective
`aramid yarns and an additional outer shell, which provides increased mechanical
`strength.
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`Duplex Zipcord
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`Zipcord Fiber Optic Cables structure contains two simplex cables jointed together; it
`can be easily split apart by hands. It is used for general indoor applications. Zipcord
`fiber optic cable can be manufactured as single mode or multimode and with various
`kinds of connectors like LC, SC, ST. Usually on the zipcord cable, each side is two
`connectors, and the two connectors may be joined together by a clip. The buffers are
`color coded for easy identification and installation. This fiber cable is perfect for data
`centers and indoor point to point connections.
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` Figure 2-6: LC, SC and ST Connectors
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`Advantages
` Standard fiber count : 2C
` Light weight and flexible
`Ideal for tight radius installation
`
` Easy termination, rugged cable-connector interface
` The simplex cords can be easily separated from each other
`Application
` For use in the cable assemblies including
` For patch panels within communication closet
` For communication closet jumper assemblies
` Suitable for dropped ceiling installation
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` Figure – 3.1
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` Figure 2.7: **OLT-Optical Line Termination; ONU-Optical Network Unit**
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`Construction
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`Figure – 2.8
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`① Optical fiber type : SMF(Sing Mode optical Fiber), MMF (Multi Mode optical
`Fiber)
`② Tight Buffer Coating : PVC or LSZH (Low Smoke Zero Halogen)
`③ Dielectric Strength Member : Aramid yarn
`④ Jacket : PVC or LSZH (Low Smoke Zero Halogen)
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`3. Multifiber Breakout Cable
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`Multifiber Breakout Cable is a favorite where rugged cables are desirable or direct
`termination without junction boxes, patch panels or other hardware is needed. They are
`made of several simplex cables bundled together inside a common jacket. This is a
`strong, rugged design, but is larger and more expensive than the distribution cables. It is
`suitable for conduit runs, riser and plenum applications. It's perfect for industrial
`applications where ruggedness is needed. Because each fiber is individually reinforced,
`this design allows for quick termination to connectors and does not require patch panels
`or boxes. Breakout cable can be more economic where fiber count isn't too large and
`distances too long, because is requires so much less labour to terminate. A breakout
`cable is used when you need to connect two areas of your infrastructure together;
`whether this is connecting floors in the same building, connecting two buildings on your
`campus or for linking deployable equipment to a control room.
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`Figure 3.1: Multi Fiber Break out Cable
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`Cable Design
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`The design of breakout-style cable adds strength for ruggedized drops, however the
`cable is larger and more expensive than distribution-style cable.
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`Since each fiber is individually reinforced, the cable can be easily divided into
`individual fiber lines. Each simplex cable within the outer jacket may be broken out and
`then continue as a patch cable, for example in a fiber to the desk application in an office
`building. This enables connector termination without requiring special junctions, and
`can reduce or eliminate the need for fiber optic patch panels or an optical distribution
`frame. Breakout cable requires terminations to be done with simple connectors, which
`may be preferred for some situations. A more common solution today is the use of a
`fan-out kit that adds a jacket to the very fine strands of other cable types. . Breakout
`Cable is by far the least expensive and easiest cable type to terminate and requires the
`least experience on the part of the installer.
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`Break Out Cable Varieties
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`•
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`Indoor/Outdoor breakout cable
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` Plenum rated breakout cable
` Riser rated breakout cable
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`Indoor/Outdoor breakout cable
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`A majority of indoor cable is used in building wiring applications. Installed in walls,
`between floors, in plenum air handling ducts and under data center floors, this indoor
`fiber cable used in building wiring applications is built to withstand the tensile stresses
`present during installation by the contractor or assembler.
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`Outdoor breakout cables have riser and plenum rated versions. These cables are
`flexible, easy to handle and simple to install. Since they do not use gel, the connectors
`can be terminated directly onto the 900µm fiber without difficult-to-use kits. This
`provides an easy and overall less expensive installation.
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`Cable cross sections:
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`Figure 3.2: Cable Cross-section
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`Temperature specifications:
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`• Storage -40°C to +70°C
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`• Operating -40°C to +70°C
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`•
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`Installation -20°C to +70°C
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`Application
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`1. Ideal for installations requiring an extremely rugged and reliable cable design
`where maximum mechanical and environmental protection are necessary
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`2. Easiest cable to install where direct termination of connectors to sub-units and
`direct run to panels and equipment is desired
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`Plenum rated Breakout Cable
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`Plenum is an air-handling, air flowing and air distribution system space which is found
`above drop ceiling tiles or heating and ventilation ducts. The outer jacket of plenum
`rated cables are made of materials that retard the spread of flame, produce little smoke
`and protect electronic equipment from damage in fires. Plenum cables can be run
`through plenum spaces without special conduits. Plenum rated cables are more
`expensive, because of the jacket material.
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`Figure 3.3: Plenum Rated Breakout Cable Cross-section
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`Temperature:
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`• Storage -40°C (-40°F) to +70°C (+158°F)
`• Operating -20°C (-4°F) to +70°C (+158°F)
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`Advantages:
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`•
`Interlock armor provides outstanding mechanical protection
`•
`Interlock armor is flexible and easy to use
`• Tight buffer provides individual fiber protection
`• Outer jacket is moisture-resistant, fungus-resistant and UV resistant suitable for
`outdoor use
`• With an overall OFNP (Plenum) rating, this cable is suitable for installations in most
`spaces requiring UL flame ratings: Plenum, Riser, General Purpose and outside
`plant
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`Riser rated Breakout Cables:
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`Riser is a pathway such as floor opening, shaft or duct that runs vertically through
`floors. Riser rated cables can be run through building vertical shafts (risers) or from one
`floor to another floor.
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`Optical fiber, nonconductive, riser (OFNR) is a type of optical fiber cable. As
`designated by the National Fire Protection Association (NFPA), this name is used for
`interior fiber-optic cables which contain no electrically conductive components, and
`which are certified for use in riser applications; they are engineered to prevent the
`spread of fire from floor to floor in a building. They are distinct from optical fiber,
`nonconductive, plenum cable
`(OFNP), and general-purpose optical cable.
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`OFNR cables can not be installed in plenum areas since they do not have the required
`fire and smoking rating as Plenum rated cables. OFNP plenum cables can be used as
`substitutes for OFNR cables.
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`CROSS SECTION:
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` Figure 3.4: Riser Rated Breakout Cable Cross-section
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`Temperature
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`• Operating temperature, range -20 .. 75°C
`• Ambient installation temperature, range -20 .. 75°C
`• Storage temperature, range -40 .. 85°C
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`Advantages
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` One cable design meeting all structured cabling network communications applications
` High tensile strength provides for greater pulling distances
` Ease of installation
` Broad design selection allows for mix and match of fiber components to specific
`networking applications
` Low cable plant maintenance
` Armor option adds crush resistance and protection from rodent attacks
`
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`Maintenance
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`The use of tight-buffered indoor/outdoor breakout cables greatly simplifies system
`maintenance and reduces restoration time. For routine terminations often required in
`moves, additions, and changes, only the skills and tooling for installing optical
`connectors are needed. Tight-buffered cables allow some portion of the fibers to be left
`dark for future termination with whatever type of connectors may be required. The
`installation of connectors on the ends of the optical fibers is the minimum skill required
`of the organization responsible for maintenance of a fiber optic cable plant.
`Emergency restoration is also made much easier when tight-buffered cables are
`involved. All of the messy cable stripping, fiber end preparation, and cleaning required
`for splicing loose-tube gel-filled cables are time consuming and more likely to be
`successful in a controlled, clean environment. Emergency restoration is most likely to
`be required in less than ideal, adverse environmental conditions of temperature, rain,
`snow, mud, etc. In tight-buffered cables there is no gel - the mess and cleaning are
`completely eliminated. If splicing should be required on a tight-buffered indoor/outdoor
`cable, the tight-buffered fibers are inherently better protected, and the repair time is
`greatly reduced.
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`4. Hybrid Cables
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`What is Hybrid Cable?
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`A hybrid fiber cable or hybrid fiber-coaxial cable (HFC cable) is a
`communication medium that combines fiber optic and coaxial cable-based transmission
`modes into a unified path. Hybrid cables incorporate mixed optical fiber with copper
`cable. This multifunctional cable is used for power and data transmission. It delivers
`voice, Internet, cable TV and other digital interactive solutions and services to
`individual consumers and organizations.
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`Figure 4.1: Hybrid Cable
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`When to use hybrid cables?
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`Hybrid cables are ideal for networks involving real-time image transport or
`sharing large files. Such applications include computer-aided design and manufacturing,
`laboratory simulators and hospital imaging systems--or, any other application that may
`require even higher bandwidths in the future.
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`Principle of Hybrid Cables:
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`Copper cables are inexpensive and installation is easier. If we send data over copper
`cable, every 30Kms we need repeaters to avoid power drop. Whereas optical fibers have
`lower transmission losses compared to copper wires. This means that data can be sent
`over long distances, thereby reducing the number of intermediate repeaters needed for
`these spans.
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`In a typical HFC cable scenario, a service provider stretches a fiber optic backbone that
`is located in close proximity to a customer/end-user and terminates it at a node device.
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`From the node device, the fiber's transmitted light signals are converted into radio
`frequency signals, which are transmitted via coaxial cable, which expands until it
`reaches the end user or device.
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`Structure of the hybrid cable
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`Hybrid fiber cable/coax cable consists of a single cable sheath that contains fibers and
`copper cables in different combination. The hybrid cable can have both the distribution
`as well as the breakout structure. For instance, cables for HDTV cameras usually base
`on the distribution structure that provides high flexibility with small diameter and low
`weight. The cable used for underground mining applications will use the breakout
`structure for better protection against mechanical tensions and working forces.
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` Figure 4.2: HDTV camera hybrid cable. Figure 4.3: Industrial hybrid cable, breakout structure
`
` (Visible optical fibers (yellow and blue), screen braid
`
` and electrical wires (red, green and black) and fillers (white))
`
`
`Figure 4.4: Cross-section of the hybrid cable Figure 4.5: Cross-section of the breakout type hybrid
`cable
`
`
`
`The combination of the diameters and gauges of the copper wires or types of the optical
`fibers is virtually unlimited and depends entirely on the customer needs and
`requirements. The copper wires can be employed to carry electrical signals or supply
`the power, so there could be a whole variety of copper cables like wires, twisted pairs,
`coax, triax, etc. This cable functions for CCTV in tunnels, buildings and airports.
`
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`Applications:
`
`HFC cable has a bright future for WAN communications as more is installed in cable
`TV infrastructure. Using HFC, cable operators can provide telephone service, multiple
`channels of interactive TV and high-speed data services for PC’s. A full HFC system
`can deliver:
`1. Plain old telephone services
`2. Over 200 digital TV channels
`3. Over 400 digital point channels (customer-requested services)
`High-speed, two-way digital data link for PCs.
`
`For example, a cable Internet Service Provider (ISP) may use fiber optic from the
`central office to each branch exchange of a town. The Internet is delivered on coaxial
`cables from there to the customer’s home or office. This combination of fiber and
`coaxial cable allows higher speeds to be reached through a fiber backbone close to the
`customer, while remaining economical and compatible via coaxial cable-based delivery
`to end users/consumers.
`
`In a hybrid fiber-coaxial cable system, the television channels are sent from the
`
`cable system's distribution facility, the hub, to local communities through optical
`
`fiber trunk lines. At the local community, a box called an optical node translates the
`
`signal from a light beam to electrical signal, and sends it over coaxial cable lines for
`
`distribution to subscriber residences. The fiber optic trunk lines provide adequate
`
`bandwidth to allow future expansion and new bandwidth-intensive services.
`
` Figure 4.6: A generic hybrid fiber coaxial (HFC) cable network
`
`
`
`Advantages and Disadvantages
`
`Advantages
`
` Cost – Less maintenance costs due to fewer amplifiers required and less
`electricity is consumed.
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` Reliability – Reliable, immune to noise and almost non-existent attenuation
`(distortion).
` Bandwidth – High bandwidth capabilities, increased from traditional CaTV
`network (up to 330MHz or 450MHz) to 750MHz with HFC.
` Flexibility – Has ability to adapt to new services such as voice, data or video
`without changing existing operational parameters (TE Consulting)
` Size – Lighter weight and thinner than copper cables with the same bandwidth,
`much less space is required in underground cabling ducts and easier for
`installation engineers to handle.
` Security – Much more difficult to tap information, a great advantage for banks
`and security installations. Immune to Electromagnetic interference from radio
`signals, car ignition systems, lightning etc. Can be routed safely through
`explosive or flammable atmospheres.
` Technology Support – Can support Cable telephones, increased number of
`CaTV channels (to over 200), a direct infrastructure to new Digital TV standards
`which assume that networks will use HFC backbones and ATM services.
` Availability – No need to dial-up or tie up a phone line as it uses a separate
`connection, Cable Internet has constant connectivity.
`
`Disadvantages
`
` Cost – More expensive than Coaxial Cable, especially costly to rural subscribers
`due to long cables required.
` Reliability – Due to the huge number of users that a fiber will support, a train
`derailment, earthquake or other
`traumatic even can have catastrophic
`proportions.
` Skill Required – Optical fibers cannot be joined (spliced) together as easily as
`copper cable and requires additional training of personnel and expensive
`precision splicing and measurement equipment.
` Symmetry – Asymmetrical, not based on new interactive multimedia. The
`upstream paths in the HFC network are slower than downstream.
` Signal Quality – Is reduced as more subscribers use the network. Speed of
`transmissions also decreases. HFC network speeds are limited by the number of
`users using the network at the same time. Even though a single 7MHz channel
`can have theoretical speeds of 30Mbps, much of this speed is shared between all
`the users on the neighborhood node using a cable modem at the same time. Each
`node
`is capable of
`supporting
`services
`to 500
`- 2000 homes.
`
`
`Future Prospects:
`
`The appeal of these high-performance cables, which typically combine both
`metallic conductors and optical fibers within the same jacket, is their long-term cost
`savings and their ability to meet the projected network performance requirements of the
`future.
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`5. Submarine Cables
`
`What is a submarine cable?
`
`A submarine communications cable is a cable laid on the sea bed between land-
`
`based stations to carry telecommunication signals across stretches of ocean. The first
`submarine communications cable was laid in the 1850s and carried telegraphy traffic.
`Subsequent
`generations
`of
`cables
`carried telephone traffic,
`then data
`communications traffic. Modern cables use optical fiber technology to carry digital
`data,
`which
`includes
`telephone, Internet and
`private
`data
`traffic.
` As of 2010, submarine cables link all the world's continents except Antarctica.
`
`
`Why not Antarctica?
` Antarctica is the only continent yet to be reached by a submarine
`telecommunications cable. All phone, video, and e-mail traffic must be relayed to the
`rest of the world via satellite, which is still quite unreliable. Bases on the continent itself
`are able to communicate with one another via radio, but this is only a local network. To
`be a viable alternative, a fiber-optic cable would have to be able to withstand
`temperatures of −80˚ C as well as massive strain from ice flowing up to 10 meters per
`year. Thus, plugging into the larger Internet backbone with the high bandwidth afforded
`by fiber-optic cable is still an as yet infeasible economic and technical challenge in the
`Antarctic.
`
`
`Why not use Satellite Communication always?
`
` Satellites have a two-fold problem: latency and bit loss. Sending and receiving
`signals to and from space takes time. Meanwhile, researchers have developed optical
`fibers that can transmit information at 99.7% the speed of light.
`
`
`
`History of Submarine cabling:
`
` The first trans-Atlantic cables were laid in the 1860s, and trans-Pacific cables
`followed in the early 1900s. These cables were incredibly low-bandwidth because
`repeaters didn’t exist then, so the only way of getting a signal