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Advantages of Fiber Optics

Fiber optic relays are quickly becoming the medium of choice for telecommunication systems, television transmission, and data networks. Fiber optic cables boast a bevy of advantages and benefits over more traditional methods of information systems, such as copper or coaxial cables.

So what are some of these advantages that make this technology so much better than metal wire? One of the greatest benefits to using optical light signals is the capacity and speed of such a system. Obviously, light travels much faster than an electrical system (as with a metal wire system), thereby allowing faster reception and delivery of information. Also, fiber optic schemes have a much higher capacity for bandwidth than those that are more traditional.

Coaxial cables are known for their susceptibility to electromagnetic interference, which can cause them to become less effective. Fiber optics, on the other hand, is not affected by external electrical signals, since data is transmitted with light. Its immunity to electromagnetic interference is another huge advantage over metal wire and coaxial channels.

Optical systems also offer more security than traditional mediums. Coaxial cables can leak information due to magnetic interference. Due to this decreased radiation, eavesdropping is made much more difficult and optical transmission mediums are currently one of the most secure methods of information transfer.

Fiber optic systems are one of the safest forms of data transmission in terms of fire prevention, as well. Metal wire forms of transmission can create sparks, causing shorts and in some cases, fire. Since optical strands use light rather than electricity to carry signals, there is no chance of starting an electrical fire. This simple fact makes fiber optics an extremely safe form of wiring, especially when compared to more dangerous traditional wire alternatives.

Fiber optic systems are much more efficient than coaxial and copper mediums because there is far less loss of data. This can be attributed to the design of optical fibers and, more specifically, the principle of total internal reflection that they use.

The cladding used in this science of light transmission also greatly increases the effectiveness of data transmission. Because of this innovation, coupled with the total internal reflection, there is no crosstalk between cables.

Fiber optic data systems have proven to be a much better alternative to traditional data communication mediums, such as copper wire and coaxial cables. As new technologies are developed, these avenues will become even more efficient, securing there place in the future of telecommunication, television, and data network industries.

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Optical Fiber Fusion Splicing and Its Applications

What is optical fiber fusion splicing?

optical fiber fusion splicing is a welded seam between two optical format. This is a permanent loss, high strength together with other joint venture as a mechanical connection. Joints in optical fiber fusion play a crucial role in the optical network.

The ideal fusion splicing process

The goal is to create a joint with minimum insertion loss with the mechanical strength and long-term reliability,Games of the fiber itself

The ideal process should be quick, inexpensive and requires no expensive equipment. But in reality the process needs to compromise between different applications and requirements. For example, submarine telecommunications, the long-term reliability is the most important goal for fusion splicing.

Benefits

There are other approaches for interconnecting fibers such as fiber optic connectors and mechanical splices. Respectthese two fusion splicing has many advantages as explained below.

Before Very compact

According Low insertion loss

Third lowest back reflection (optical return loss ENT)

Fourth Highest mechanical strength

Fifth Permanent

Sixth Supports up to extreme temperature changes high

Seventh Prevents dust and other contaminants from entering the optical path

Many types of splicing

Fusion splicing environment and applications can be divided into three groupsTypes: a second field splicing Factory Labor splicing and 3-splicing.

An important example of field assembly of splicing fiber optic submarine on board ships is to build fiber optic networks. The example of factory splicing could be the installation of fiber optic passive devices such as a WDM. An example of laboratory-splicing is made from the latest fiber fusion splicing researchers developed their compatibility with current industry standard test fiber.

Fiber fusion splicingincludes concepts from many areas, including fiber optics theory, heat transfer, materials science, mechanical engineering, aerodynamics and more.

Introduction to the process of splicing

The main steps can be summarized as follows.

1.Optical fiber stripping

The jacket is removed and the polymer coating of optical fiber cable fiber optic fiber is stripped strippers.

2.Fiber attachment

The fiber is cleaved withspecialized tool called Fiber Cleaver. Two types of fibers exist Cleaver: Cleaver Fiber High precision single-mode applications and the cleaver field for multimodal applications. A mirror, as almost perfect face is obtained from the fission process.

3.Fiber Guidance

The fibers are laterally approximated by step motor in a fusion splicer. This may mean turning the polarization maintaining fiber-fiber joints.

4.Fiber welding

The fibers are thenheated by electric arc or other methods to increase softening point of the fiber and then the two fibers together, pressed to form a solid joint.

5.Insertion loss estimation

The insertion loss estimate based on fusion of quality and / or weight.

tensile tests 6.Pull

The merger is intended to cover the opening of the head pull test fusion splicer.

7.Splice splice protection sleeve

The articulation joint fusion is then protected with shrink tubingwith a member strength steel in forming a solid and reliable fiber common.

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HDMI Cables - How Can I Boost the Signal So it Travels Further?

HDMI offers home entertainment enthusiasts unparalleled digital audio and picture quality and is practically the de facto standard connection type across the globe as more and more manufactures are now replacing outdated connections with HDMI; however, there are some limitations to the platform. HDMI cables were never designed to perform over long distances, so this article will look at how you can boost the signal strength when using long runs of cable.

As with practically any other type of cable, the further the signal has to travel, the weaker is gets. Therefore the majority of HDMI cables offer the highest levels of performance over relatively short runs of about 15 feet or so. Once you start using longer runs the signal starts to become noticeably degraded, and if you run your HDMI cable over 40 or 50 feet then you will undoubtedly run into problems.

If HDMI Is So Good, Why Can't It Handle Long Distances?

HDMI cables are made using twisted pairs of copper wires, and over long distances the signal can actually start being reflected along the cable, which in turn can cause interference resulting in poor quality output. The maximum run length that a cable is effective over is different for each cable and is dependant on the quality of the raw materials used in the manufacturing process, and the standard to which the cable was made. Generally speaking, higher quality cables use thicker copper wire in the twisted pairs and while this increases the cost to the consumer, it does mean that the signal is able to be effective over a longer run.

Even the best quality HDMI cables struggle to transfer strong signals over distances of 50 feet; so if you need your HDMI cable to be effective over long distances then you will have to invest in some additional devices to help boost the signal.

What Are The Options?

Fortunately there are many different devices out there to help your HDMI signal travel long distances; the most common include signal boosters and restorers, extenders and even fibre optic cables. Choosing the right option for you can be hard, as the cost and effectiveness of the solution can vary widely, so here is a brief overview of each one.

Signal Boosters - as the name suggests, these devices boost the strength of the signal so that it remains strong even after traveling long distances. Signal boosters also allow you to 'daisy chain' shorter cables together, which may be a cheaper option than buying one long run of cable.

Signal Restorers - these are small devices that re-synchronize a weak signal back up to full HDMI quality. The device is placed at the end of the HDMI cable, and can help to extend the distance the signal can travel by over 100 feet.

Signal Extenders - are very similar to signal boosters and allow you to daisy chain multiple HDMI cables together in order to extend the effective distance the signal can travel.

Fibre Optic Cable - is the most expensive option and is used when the HDMI signal needs to cover very long distances. By using fibre optic cable it is possible for a HDMI signal to travel over 1,500 feet.

Conclusion

As you can see there are several different methods you can use in order to extend the distance that your HDMI signal can travel without degradation. Each has its benefits and drawbacks, so take some time to research each option in order to choose the solution that is most suited to your personal needs.

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A Brief Introduction to Communication Systems

The original telecommunication system was developed for PSTN (Public Switch Telephone Network) for voice communications. But now communication networks include all types of voice, video and data communication over copper wire, optical fibers and wireless medium.

With the inception of Internet, increasingly numbers of computer networks are now connected via the Internet. So now the concept of telecommunication system has increased complexity significantly. These systems can be divided into different types by the information they carry. With this kind of categorization, communication systems can be categorized as long-haul point-to-point links, distribution networks, MAN (metro area network) and WAN (wide area network).

Now let's examine them one by one.

1. Public Switched Telephone Network (PSTN)

This network connects billions of users by switches, routers or other dedicated connections. It was designed to carry voice only at first, but with enhanced services, they can carry digital data information as well.

Computers with modems can transmit and receive digital data via the PSTN network with enhanced data services such as DSL.

2. Cable TV systems

CATV is still the biggest player for television broadcasting. But now they are facing competitions from Satellite, DSL video on demand. CATV providers also entered into data communication market and VoIP services.

3. Data Networks

With modern telecommunication systems, all information are transmitted in digital form. These digital networks can be categorized based on network topology, switching technology and the communication protocols.

The switching technologies used in modern networks can be categorized as circuit switching and packet switching. Circuit switching is used mostly for voice networks but not very efficient. Packet switching can route data packet according to the least busy path and it provides a virtual connection.

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How Does Fibre Optic Technology Work?

In recent times fibre optic technology has become increasingly evident in all types of technology. Gone are the conventional methods of sending data through copper wires, as well as slow data transfer speed. In this article I will explain the technology behind optic technology and what is involved.

How are fibre optics constructed?

Fibre optic cables are made up of minuscule strands of glass and plastic. In a lot of cases these filaments are purely glass such as those used to transfer cable broadband. The reason for this is that glass reduces signal loss over long distances while plastic is commonly used for short distances.

These filaments are interwoven on top of a core known as cladding. Cladding is what keeps the signal within the centre core, as the cladding is reflective light is directed to stream through the centre core while also preventing loss of signal which could be lost.

Types of optic

Multimode fibres

Multimode fibre optics are commonly used for short distance transfer where high power output is needed. These type of fibres come with a larger core to deal with the extra power output.

Singlemode Fibres

These fibres allow only one single at a time and are commonly used for long distances that multimode is not suitable for.

How is data transmitted via fibre optics using light

Many people assume the light transmitted through optics is one single strong beam of light. In fact the light passed through a fibre optic cable is regulated in short bursts of various lengths and timing. This could be compared to technology and data transmission such as morse code for example.

Optical connections provide many benefits over the standard copper wire transfer including faster and higher data transfer as well as being more reliable than copper transmission. You would think a technology like this would be expensive, but in fact optics is cheaper and more cost efficient than copper transfer methods.

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Universal Conduit Elbow

In most applications, the LU can replace the LL, LR, LB and C conduit bodies. The patent-pending, unique and innovative design of the Universal Conduit Elbow provides an angled covered port, allowing it to be flipped over and used as an LL, LR or LB, while providing easy access against walls and ceilings. The LU was specifically designed to have more volume, allowing a 40 percent wire fill and preventing the conduit system from being de-rated, a problem common with other conduit bodies. The LU can be used to replace the C conduit body when code requires an inspection port after a 90-degree bend. Simply use the LU to replace the 90 and the C and it will provide the bend and inspection port all in one part. Aside from its universality, the LU Elbow offers additional benefits. The LU enables electricians to run fiber optic cable in a 3⁄4-inch system—and maintain cable bend radius—instead of in a 2-inch system, and it is resistant to both internal and external corrosion with quality BlueKote® four-layer protection. Look for it soon in stainless steel and aluminum. Because the radius of the LU Elbow is the same as the bent conduit, it makes pulling wires hassle-free.

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MaximsNewsNetwork: AFRICA - WORLD ECONOMIC FORUM (IFAD)

MaximsNewsNetwork: 04 May 2010 - IFAD: Tanzania - As Tanzania gears up to host the 2010 World Economic Forum on Africa, the UN International Fund for Agricultural Development reports that the country's recent technological developments in communications could revolutionize the lives of Tanzanians. The growth in mobile phone use as a powerful economic indicator will be one of the key issues influential business leaders, government officials and members of the civil society gathering at the Forum will discuss. In Africa, mobile use soared by 550 percent in the last five years according to a report by the United Nations (UN) Conference on Trade and Development (IFAD) published in October 2009. Mobile subscriptions rose from 54 million to almost 350 million between 2003 and 2008. IFAD in partnership with the Tanzanian Government has helped to develop Mobilinfo, a software platform which is the hub of an information network. From its base in Dar-es-Salaam, it reaches past Lake Victoria into Uganda and across the Massai Mara into Kenya, linking up poor farmers into a marketing network that aims to help increase incomes, reduce waste and reform markets across the region. The network is made up of hundreds of entrepreneurs who collect information from markets and exchange it on the Mobilinfo platform. That information might be about the price of a commodity at a certain market or about a buyer looking for a specific product. SOUNDBITE (English) Jakaya Mrisho Kikwete, President ...

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Saudi Telecom Company, STC (Arabic: شركة الاتصالات السعودية‎) is a Saudi Arabia-based telecommunications company that offers landline, mobile and Internet services. STC (Saudi Telecom) is the nati... Saudi Telecom Company, STC (Arabic: شركة الاتصالات السعودية‎) is a Saudi Arabia-based telecommunications company that offers landline, mobile and Internet services. STC (Saudi Telecom) is the national telecommunications services provider in the Kingdom of Saudi Arabia with a workforce of more than 21000 employees servicing their customers. Supported by the largest infrastructure in the Middle East. STC provides four key services: (A) Home services, which includes PSTN, broadband DSL; (B) Personal services, which includes mobile telephone services, and value added services; (C) Enterprise, which provides advanced business data solutions provider; (D) Wholesale, provides network services to other local operators. In the recent years STC grew beyond its local borders and went global forming a network of business and investments in various Gulf countries, Asia, and Africa. The Company is present in Kuwait, Bahrain, India, Indonesia, Malaysia, Turkey, and South Africa enabling it to provide services to a bigger customer base and increasing its total number of customers externally by studying and evaluating investment opportunities. Reflecting its strong financial position, Saudi Telecom Company was rated for the first time by Standard & Poor's Ratings Service and Moody's Investors ...

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Installing a Fibre Optic Network - Understanding the Basics

We will try to give a basic overview of fibre optic systems and how to avoid any problems when installing a fibre optic cable. Also addresses are some serious safety procedures to be aware of. 

Safety first.

When installed on a live system, do not stare down the connector as invisible laser radiation will be present and can seriously damage your eyesight. 

You must also wear safety glasses when working with fibre optics, as the tiny glass tubes can shatter and particles of glass can go in your eyes and hands. 

For a proper fibre optic cable installation, it is vital to understand the cable specifications, the two most important specifications are the tensile loading and bend radius, it is paramount that these are adhered to. 

Tensile loading.

The maximum load installation is one of the two different types of tension fibre comes under. It is sometimes referred to as the dynamic load, short term tension and installation tension. 

This tension should be monitored with either a pulling wheel or a dynamometer and is measured in Newton and pounds. Breakaway eyes are available that separate when a preset load is reached. 

When pulling cable vertically, make sure you are aware of the cable weight and install cables in a sequence that applies the least amount of strain on any cable. For example most building chasers are congested at lower levels, instead start the installation at the top of the building and work down, this way you are less likely to encounter previous cable installations. 

Bend Radius.

Two types of bend radii exist, so we will try to explain them. 

Short term minimum bend radii

This is the tightest recommended bend type while installing cable at the maximum rated tension. And a rough guide is 15 times the cable diameter. 

Long term bend radii.

Sometimes referred to as a static bend type is the tightest recommended bend radius while installing cable at the minimum rated tension. It is the small of the two bend radii. A comparable guide is 10 times the cable diameter.

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Broadband - Fibre Technology in the UK

When it comes to broadband technology, consumers will ultimately ask for their connections to eventually be faster and more reliable.

As more of us are turning towards high-definition television and more advanced video games consoles, our need for a faster connection in order to make the most of their systems is paramount to our digital experience.

Indeed, consumers are making use of broadband speed tests to check if they are getting the connections speeds promised when initially signing up for plans.

Popularity of broadband technology has increased over the years - as has the popularity of online services such as social networking, peer-to-peer networks and online video sharing websites such as YouTube.

As services such as online gaming, online video messaging and DVD-quality downloads help to fuel demand for super-fast, cheap broadband connections, providers find themselves having to think of new ways to upgrade their networks and increase connectivity for their customers.

One such idea is to thread a new network of cables through the sewers beneath our feet. With over 360,000 miles of pipeline beneath our feet, the possibilities for deploying cables that contain fibre networking seem endless.

As fibre optic wires are made of glass, electrical signals travel faster than a copper wire system, and the wires themselves are less prone to corrosion when immersed in water.

Even the installation process could save time and ease congestion, as there would most likely be no need to dig up the road in order to lay the cable, they could simply be threaded through the vast network of pipeline already laid.

And the south-west coastal town of Bournemouth in Dorset has recently been selected to become the first town in the UK to provide consumers with high-speed broadband access, with work scheduled to begin 'within the next six months'

Businesses and universities around the country have already seen the benefits of such schemes, and now it appears that the idea is being rolled out to include members of the general public, with further projects to deliver fibre networking to more consumers planned for the future.

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Chuck Hughes: Buy Google

There is a major technology shift occurring that will bring an end to the PC as we know it. Gone will be the days when we would go out to the local computer store and buy application or operating system software and install it on our PC. In the not too distant future your monitor will be connected to what is called the cloud database that contains all of the applications and operating systems you need making the PC obsolete. The first stage of the cloud database is already a reality. When you find driving directions on Map Quest, watch a video on YouTube, conduct a data search on Google or sell your car on Craigslist all you need is a monitor with an Internet connection. Although these activities require you to use your PC, none of the content you are accessing or the applications you are using are actually stored on your PC hard drive. Instead they are stored in a giant data network or cloud. This technology shift will forever change the way we get information and do business. Due to the thousands of miles of fiber-optic cable installed during the last 10 years, the speed of computer networks has finally exceeded the speed of computer processors. Computers that were once incompatible and isolated are now linked in a giant network, or cloud that contains a database of applications and operating systems that only require a monitor and Internet connection. The management team at Google has positioned the company to be the leader in the technology shift to cloud databases ...

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How To Install Outdoor Fiber Optic Cables In Underground Ducts And Innerducts

:: Duct/Innerduct materials and colors:

Fiber ducts are usually made from HDPE (high-density polyethylene), PVC or other compound. They are usually in black or gray. Fiber innerduct is usually orange or yellow.

:: Why usually fiber ducts and innerducts are corrugated?

Fiber ducts and innerducts are corrugated to provide the following benefits:

1. Decreasing pulling tensions during installation

2. Very flexible and can be used in installation locations where many turns are involved

3. After installation, corrugated innerduct should be left for a day to allow the innerduct to retreat back into the duct through its corrugated spring action

:: The use of pulling tape

Fiber optic cable pulling tape is preinstalled in fiber duct and innerduct in the factory. This saves significant time during the installation process. Duct and innerduct can also be pre-lubricated in the factory, thus significantly reduces pulling tensions.

:: Never bend over its minimum bend radius

Just like fiber optic cable, fiber duct and innerduct also have a minimum bend radius spec. Never ever should the duct or innerduct be bent tighter than its minimum bend radius.

:: What is supported radius?

The supported radius is the minimum bend radius when the duct is bent around a supporting structure such as in another duct or on a reel.

:: What is unsupported radius?

The unsupported radius is the minimum bend radius when the duct has no supporting structure in the bend.

:: Benefits of using fiber duct

Fiber duct protects the fiber cable and also provides an opportunity for future cable access and expansion. Fiber optic cable can be pulling into existing duct. The duct should usually be oversized to allow future cables be pulled in.

:: Benefits of using fiber innerduct

Fiber innerduct provides protection for the fiber cable from being disturbed by other companies' cable installation operation. It also provides extra protection from the environment. Or fiber innerduct can be used in old duct installation.

:: Things to keep in mind

1. Install end plugs

After the fiber optic cable is installed into a duct or innerduct, end plugs should be installed to provide a water seal. No debris should be able to enter the duct or innerduct, and watertight should always be maintained for the duct or innerduct.

2. Duct and innerduct should be properly sized for future expansion possibility

As always, planning for future expansion is crucial for real successful projects. A maximum of 40% fill ratio is a good practice to follow. The duct size should be increased for long installation lengths with many turns. A larger duct can help to reduce cable-pulling tensions. Standard duct sizes vary from 3 to 8 inch ID and innerduct sizes vary from 0.75 to 2 inch.

:: The benefit of using duct lubricant

Duct lubricant can significantly reduce the cable's coefficient of friction, thus lessening the pulling tension during cable pulling process. This is especially important in long cable duct pulls and pulls with many turns.

Duct lubricant spillage should be cleaned up as soon as possible to prevent accident since it is very slippery. Manufactures' recommended procedure for cleaning lubricant provides good instruction on how to do the cleaning.

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Advantages of Fiber Optic Cable Over Copper Wire

When dealing with data transmission you have two basic options: fiber or copper. The final choice depends on a wide variety of variables but ultimately fiber optic cable will be the data transmission of choice for your new network as well as the replacement of old configurations. Fiber optic cable is becoming one of the fastest growing transmission mediums for a variety of applications. Some of the more favorable applications include high band width, long distances and complete immunity to electrical interference. One of the most common applications is as a network backbone, where large amounts of data are transferred.

Other features include the use of singlemode and multimode cables. One singlemode fiber can replace a metal cable that is a thousand times larger and heavier. Multimode cables on the other hand have a larger diameter and are used to carry signals over shorter distances. Other advantages of fiber optic cable include a longer life expectancy, low system cost, no shock hazard, no sparks if cut and low attenuation. Fibers are also used for illumination and are wrapped in bundles so they can be used to carry images, thus allowing viewing in tight spaces.

To make a long story short, fiber optic cable is the future and copper wiring is one of the oldest transmission channels in use today. Some of the main disadvantages of copper are the high costs and the susceptibility to corrosion and rain. Due to the advantages of fiber and the disadvantages of copper, telecommunication companies around the world are using nothing but fiber optic cables and are replacing all of their older cable systems with fiber.

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SC Connector How-To Video

Step by Step how-to video on assembling an SC connector on a pre-terminated ferrule connection on a fiber optic spool

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FAQ On Fiber Optic Cable Handling And Installation

1. What is the difference between copper cable and fiber optic cable?

Even though fiber optic cables may look like traditional copper cables, we should always keep in mind that inside fiber cables are fragile glass fibers which can be broken easily if not properly handled.

2. What are the most important things to obey in fiber cable installation?

During any fiber optic cable installation project, we must keep two very important things in mind: First, never over-bend the fiber cable over its minimum bend radius. Second, never pull over the cable manufacturer's cable pulling tension specification.

3. What is Minimum Bend Radius (MBR)?

Fiber cables all have a minimum bend radius specification by the manufacturers. This the minimum curve radius while bending the fiber cable in either installation process or after the installation in its final resting position. You can make larger curves but never smaller than specified.

4. What is Loaded MBR?

It is the fiber cable bend radius specification during a cable pull as in the installation process. The cable must not bend tighter than its loaded MBR at any time during the installation process. Loaded MBR is larger than unloaded MBR as explained below.

5. What is Unloaded MBR?

It is the fiber bending radius specification in the cable's final resting position after installation. That is when the cable is not under any tension. Often, this spec is determined by a simple multiplication such as 15~25 X OD (fiber cable outside diameter).

6. What is Fiber's MBR?

Fiber optic cables are composed of individual fibers (strands). Individual fibers also have a minimum bend radius specification, which is usually 2~3 cm and is much smaller than jacket cables.

7. What will happen if a fiber cable is bent smaller than its minimum bend radius?

Bending a fiber cable over its MBR is one of biggest factors in fiber damaging in fiber cable installation projects. This practice can either break the inside fibers or increase fiber attenuation (fiber power loss) over the manufacturer's specification. Even if the inside fibers are already broken, you may not see any physical damage to the outside jacket at all. The consequence is, you have to replace the whole section or even the entire length of cable. As a good practice, all fibers need to be thoroughly tested after cable installation.

8. What is Pulling Tension?

Pulling tension is the force placed on per square unit of fiber cable cross section. Maximum pulling tensions during fiber cable installation are specified by cable manufacturers and should not be exceeded at any time. Most tensile load on a cable will occur in a vertical installation and is caused by the cable's own weight.

9. Other Fiber Optic Cable Installation Tips

a. The cable should be pulled by hand as much as possible

b. Pulling tension should always be monitored when using mechanical pulling techniques

c. Cable should be pulled in a steady, continuous motion and never jerked

d. Never push a fiber optic cable

e. Using the minimum possible tension while pulling fiber cables

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Introduction To IP Addressing And Networking

NETWORKING BASICS

A network can be defined as the interconnection of autonomous computers linked together to facilitate communication while networking is the simple concept of connected computers.

Networks and networking have grown exponentially over the last 15years; they have evolved at light speed just to keep up with huge increases in basic critical user needs such as sharing data and printers, as well as more advanced demands such as video conferencing.

TYPES OF NETWORKS

LOCAL AREA NETWORK (LAN)

A LAN (Local Area Network) is a group of computers and network devices connected together, usually within the same building. A Local Area Network (LAN) is a high-speed communication system designed to link computers and other data processing devices together within a small geographical area, such as a workgroup, department, or building. Local Area Networks implement shared access technology. This means that all the devices attached to the LAN share a single communications medium, usually a coaxial, twisted pair or fibre optic cable.

METROPOLITAN AREA NETWORK (MAN)

Metropolitan area networks or MANs are large computer networks usually spanning a city or a town. They typically use wireless infrastructure or optical fibre connections to link their sites.

The IEEE 802-2001 standard describes a MAN as being: "A MAN is optimized for a larger geographical area than is a LAN, ranging from several blocks of buildings to entire cities. MANs can also depend on communications channels of moderate to high data rates. A MAN might be owned and operated by a single organization, but it usually will be used by many individuals and organizations. MANs might also be owned and operated as public utilities. They will often provide means for internetworking of local networks. Metropolitan area networks can span up to 50km."

WIDE AREA NETWORK (WAN)

Wide Area Network (WAN) is a computer network that covers a broad area. A WAN in compares to a MAN, is not restricted to a geographical location, although it might be restricted to a geographical locations, it might also be confined within the bounds of a state or country. A WAN connects several LANs, and may be limited to an enterprise (a corporation or organization) or accessible to the public.

The technology is high speed and relatively expensive. The INTERNET is an example of a worldwide public WAN.

NETWORKING DEVICES

ROUTERS

Routers are used to connect networks together and route packets of data from one network to another. Routers, by default break up a broadcast domain, which is the set of all devices on a network segment that hear all broadcasts sent on that segment.

Routers also break up collision domains. This is an Ethernet term used to describe a network scenario where one particular device sends a packet on a network segment, forcing every other device on that segment to pay attention to it. At the same time, a different device tries to transmit, leading to a collision, after which both devices must retransmit one at a time.

Routers run on the layer 3 of the OSI (Open System Interconnection) reference model.

SWITCHES

Switches are used for network segmentation based on the MAC addresses. Switches look at the incoming frame's hardware addresses before deciding to either forward the frame or drop it.

Switches break up collision domains but the hosts on the switch are still members of one big broadcast domain.

HUB

A hub is really a multiple port repeater. A repeater receives a digital signal and re-amplifies or regenerates that signal, and then forwards the digital signal out all active ports without looking at any data. An active hub does the same thing. This means all devices plugged into a hub are in the same collision domain as well as in the same broadcast domain, which means that devices share the same bandwidth. Hubs operate at the physical layer of the OSI model.

IP ADDRESSING

An IP address is a numeric identifier assigned to each machine on an IP network. It designates the specific location of a device on the network. An IP address is a software address and designed to allow host on one network to communicate with a host on a different network regardless of the type of LANs the hosts are participating in.

IP TERMINOLOGIES

Bit: A bit is one digit, either a 1 or a 0.

Byte: A byte is 7 or 8 bits, depending on whether parity is used.

Octet: An octet, made up of 8 bits is just an ordinary 8 bit binary number. In most cases byte and octet are completely interchangeable.

Network address: This is the designation used in routing to send packets to a remote network. For example 10.0.0.0, 172.16.0.0, and 192.168.10.0 are network addresses.

Broadcast address: The address used by applications and hosts to send information to all nodes on a network is called the broadcast address. Examples include 255.255.255.255 which is all networks, all nodes; 172.16.255.255, which is all subnets and hosts on network 172.16.0.0.

HEIRARCHICAL IP ADDRESSING SCHEME

An IP address consists of 32 bits of information (IPV4). IPV6, a new version of IP consists of 128 bits of information. The 32 bits IP is divided into four sections referred to as octet or bytes each containing 1 byte (8bits).

An IP address is depicted using any of these 3 methods.

Dotted decimal, as in 172.16.30.56

Binary, as in 10101100.00010000.00011110.00111000

Hexadecimal, as in AC.10.1E.38

All this examples represent the same IP address. But the most commonly used is the dotted decimal. The Windows Registry stores a machine's IP address in hex.

The 32 bit IP address is a structured or hierarchical address, as opposed to a flat non hierarchical address. Although either type of addressing scheme could have been used, hierarchical addressing was chosen for a good reason. The advantage of this scheme is that it can handle a large number of addresses, namely 4.3 billion (a 32 bit address space with two possible values for each position that is either 1 or 0 gives 237, or 4,294,967,296).

The disadvantage of the flat addressing scheme relates to routing. If every address were unique, all routers on the internet would need to store the address of each and every machine on the internet. This would make efficient routing impossible.

NETWORK ADDRESS RANGE

The network address uniquely identifies each network. Every machine on the same network shares that network address as part of its IP address. In the IP address of 172.16.30.56, 172.16 is the network address.

The node address is assigned to and uniquely identifies each machine on a network. This number can also be referred to as host address. In 172.16.30.56, 30.56 is the node address. Class A network is used when a small number of networks possessing a very large number of nodes are needed. Class C network is used when numerous networks with a small number of node is needed.

CLASS A ADDRESSES

The first bit of the first byte in a class A network address must always be off or 0. This means a class A address must be between 0 and 127, inclusive.

0xxxxxxx.hhhhhhhh.hhhhhhhh.hhhhhhhh

If we turn the other 7 bits all off and then turn them all on, we'll find the class A range of network addresses.

00000000 = 0

01111111 = 127

Class A format is network.node.node.node, so for example in the IP address 49.22.102.70, the 49 is the network address and 22.102.70 is the node address. Every machine on this particular network would have the distinctive network address of 49.

CLASS B ADDRESSES

The first bit of the first byte must always be turned on, but the second bit must always be turned off.

01xxxxxx.xxxxxxxx.hhhhhhhh.hhhhhhhh

If we can turn the first bit on and the second bit off and if the other 6 bits all off and then all on, we'll find the class B range of network addresses.

10000000 = 128

10111111 = 191

Class B format is network.network.node.node, so far in the IP address 132.163.40.57, the 132.163 is the network address and 40.57 is the node address.

CLASS C ADDRESSES

The first and second bit of the first byte must always be turned on, but the third bit can never be on.

110xxxxx.xxxxxxxx.xxxxxxxx.hhhhhhhh

If we turn the first and second bit on and the third bit off and then all other 5 bits all off and all on, we'll find the class C range of network address.

11000000 = 192

11011111 = 223

Class C format is network.network.network.node, for example in the IP address 195.166.231.75, the 195.166.231 is the network address and 75 is the node address.

CLASS D AND CLASS E ADDRESSES

The address between 224 and 255 are reserved for class D and E networks. Class D (224-239) is used for multicast addresses and class E (240-255) for scientific purposes.

PRIVATE IP ADDRESSES

Private IP addresses are those that can be used on a private network, but they're not routable through the internet. This is designed for the purpose of creating a measure of well-needed security, but it also conveniently saves valuable IP address space. If every host on every network had to have real routable IP addresses, we would have run out of IP addresses to hand out years ago.

Class A 10.0.0.0 through 10.255.255.255

Class B 172.16.0.0 through 172.31.255.255

Class C 192.168.0.0 through 192.168.255.255

TROUBLESHOOTING IP ADDRESSING

Here are the troubleshooting steps in resolving a problem on an IP network.

1. Open a DOS window and ping 127.0.0.1. This is the diagnostic or loopback address, and if you get a successful ping, your IP stack is considered to be initialized. If it fails, then you have an IP stack failure and need to reinstall TCP/IP on the host.

2. From the DOS window, ping the IP addresses of the local host. If that's successful, then your Network Interface Card (NIC) card is functioning. If it fails, then there is a problem with the NIC card. This doesn't mean that a cable is plugged into the NIC, only that the IP protocol stack on the host can communicate to the NIC.

3. From the DOS window, ping the default gateway. If the ping works, it means that the NIC is plugged into the network and can communicate on the local network. If it fails, then you have a local physical network problem that could be happening anywhere from the NIC to the gateway.

4. If steps 1 through 3 were successful, try to ping the remote server. If that works then you have IP communication between then local host and the remote server, you also know that the remote physical network is working.

5. If the user still can't communicate with the server after steps 1 through 4 were successful, then there's probably a resolution problem and there is need to check the Domain Name Server (DNS) settings.

NETWORK ADDRESS TRANSLATION

Network Address Translation (NAT) is used mainly to translate private inside addresses on a network to a global outside address. The main idea is to conserve internet global address space, but it also increases network security by hiding internal IP addresses from external networks.

TABLE 3: NAT ADVANTAGES AND DISADVANTAGES

ADVANTAGES

Conserves legally registered addresses.

Reduces address overlap occurrence.

Increases flexibility when connecting to internet.

Eliminates address renumbering as network changes.

Translation introduces switching path delays

DISADVANTAGES

Loss of end-to-end traceability

Certain applications will not function with NAT enabled.

TYPES OF NAT

Static NAT: This type of NAT is designed to allow one-to-one mapping between local and global addresses. Static NAT requires that there is one real internet IP address for every host on your network.

Dynamic NAT: This version gives one the ability to map an unregistered IP address to a registered IP address from out of a pool of registered IP addresses.

Overloading: This is also known as Port Address Translation (PAT). It is the most popular type of NAT configuration. Overloading is a form of dynamic NAT that maps multiple unregistered IP address to a single registered IP address by using different ports. With overloading thousands of users can connect to the internet using only one real global IP address.

NAT TERMINOLOGIES
Local addresses: Name of local hosts before translation.

Global addresses: Name of addresses after translation.

Inside local: Name of inside source address before translation.

Outside local: Name of destination host before translation.

Inside global: Name of inside hosts after translation

Outside global: Name of outside destination host after translation.

LAYER2 SWITCHING

Layer2 switching is the process of using the hardware address of devices on a LAN to segment a network. The term layer2 switching is used because switches operate on the data-link layer which is the second layer of the OSI reference model.

Layer2 switching is considered hardware-based bridging because it uses specialized hardware called an application-specific integrated circuit (ASIC). ASICs can run up to gigabit speeds with very low latency rates.

Switches read each frame as it passes through the network, the layer2 device then puts the source hardware address in a filter table and keeps track of which port the frame was received on. The information (logged in the switch's filter table) is what helps the machine determine the location of a specific sending device. After a filter table is built on the layer2 device, it will only forward frames to the segment where the destination hardware is located. If the destination device is on the same segment as the frame, the layer2 device will block the frame from going to any other segments. If the destination is on a different segment, the frame can only be transmitted to that segment. This is called TRANSPARENT BRIDGING.

When a switch interface receives a frame with a destination hardware address that isn't found in the device filter table, it will forward the frame to all connected segments. If the unknown device that was sent the frame replies to this forwarding action, the switch updates its filter table regarding that device's location.

ADVANTAGES OF LAYER2 SWITCHING

The biggest benefit of LAN switching over hub-centred implementations is that each device on every segment plugged into a switch can transmit silmatenously whereas hubs only allow one device per network segment to communicate at a time.

Switches are faster than routers because they don't take time looking at the Network layer header information. Instead, they look at the frame's hardware address before deciding to either forward the frame or drop it.

Switches create private dedicated collision domains and provide independent bandwidth on each port unlike hubs. The figure below shows five hosts connected to a switch, all running 10Mbps half-duplex to the server. Unlike the hub, each host has 10Mbps dedicated communication to the server.

LIMITATIONS OF LAYER2 SWITCHING

Switched networks break up collision domains but the network is still one large broadcast domain. This does not only limits your network's size and growth potential, but can also reduce its overall performance.

FUNCTIONS OF LAYER2 SWITCHING

There are three distinct functions of layer2 switching, these are

Address learning.

Forward/filter decision

Loop avoidance.

ADDRESS LEARNING

When a switch is first powered on, the MAC forward/filter table is empty. When a device transmits and an interface receives the frame, the switch places the frame source address in the MAC forward/filter table, allowing it to remember which interface the sending device is located on. The switch then has no choice but to flood the network with this frame out of every port except the source port because it has no idea where the destination device is actually located.

If a device answers the flooded frame and sends a frame back, then the switch will take source address from that frame and place that MAC address in its database as well, associating this address with the interface that received the frame. Since the switch now has both of the relevant MAC addresses in its filtering table, the two devices can now make a point to point connection. The switch doesn't need to flood the frame as it did the first time.

If there is no communication to a particular address within a certain amount of time, the switch will flush the entry from the database to keep it as current as possible.

FORWARD/FILTER DECISIONS

When a frame arrives at a switch interface, the destination hardware address is compared to the forward/filter MAC database. If the destination hardware address is known and listed in the database, the frame is sent out only the correct exit interface.

The switch doesn't transmit the frame out any interface except for the destination interface. This preserves bandwidth on the other network segments and is called FRAME FILTERING.

LOOP AVOIDANCE

When two switches are connected together, redundant links between the switches are a good idea because they help prevent complete network failures in the event one link stops working.

Redundant links are extremely helpful but they often cause more problems than they solve, this is because frames can be flooded down all redundant links silmatenously creating network loops.

Switches use a protocol called STP (Spanning Tree Protocol) created by Digital Equipment Corporation (DEC) now Compaq to avoid network loops by shutting down redundant links. With STP running, frames will be forwarded only on the premium STP-picked link.

CONFIGURING THE CISCO 2950 CATALYST SWITCH FAMILY.

The 2950 switch is one of the Cisco Catalyst switch family's high-end model. The 2950 comes in many flavours and run 10Mbps all the way up to 1Gbps switched ports with either twisted-pair or fibre. They can provide basic data, video and voice services.

2950 SWITCH STARTUP

When the 2950 switch is first powered on, it runs through a Power-on-Self-test (POST). At first all port LEDs are green, and if upon completion the post determines that all ports are in good shape, all the LEDs blink and then turn off. But if the POST finds a port that has failed both the system's LED and the port's LEDs turn amber.

However, unlike a router, the switch is actually usable in Fresh-out-of-the-box condition. You can just plug the switch into your network and connect network segment together without any configuration.

To connect to the Cisco switch, use a rolled Ethernet cable to connect a host to a switch console serial communication port. Once you have the correct cable connected from your PC to the Cisco switch, you can start HyperTerminal to create a console connection and configure the device as follows:

1. Open HyperTerminal by clicking on start button and then All programs, then Accessories, then Communication, then click on HyperTerminal. Enter a name for the connection. It is irrelevant what you name it. Then click OK.

2. Choose the communication port either COM1 or COM2, whichever is open on your PC.

3. Now at the port settings. The default values (2400bps and no flow control hardware) will not work, you must set the port settings as shown in the figure below.

Notice that the bit rate is set to 9600 and the flow control is set to none. At this point click OK and press the Enter key, and you should be connected to your Cisco switch console port.

Here's the 2950 switch's initial output:

--- System Configuration Dialog ---

Would you like to enter the initial configuration dialog? [Yes/no]: no

Press RETURN to get started!

00:04:53: %LINK-5-CHANGED: Interface Vlan1, changed state to administratively down

00:04:54: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down
Switch>

THE CONFIGURATION

The switch> prompt is called the user exec mode and it's mostly used to view statistics. You can only view and change configuration of a Cisco switch in privileged exec mode which you get into with the enable command.

Switch>

Switch> enable

Switch#

Switch# disable

Switch>

The global configuration mode can be entered from the privileged mode by using the configure terminal command or config t for short.
Switch# config t
Enter the configuration commands, one per line, End with CNTL/Z.
Switch(config)# hostname zenith
Zenith(config)#

The hostname command is used in naming the switch. The hostname of a switch is only locally significant but it's still helpful to set a hostname on a switch so that you can identify the switch when connecting to it.

SETTING THE ENABLE MODE PASSWORDS AND LINE PASSWORD.

Zenith> enable

Zenith# config t

Enter the configuration commands, one per line, End with CNTL/Z.

Zenith(config)# enable password bank

Zenith(config)# enable secret middle

The enable password bank command sets the enable password as bank and the enable secret middle command sets the enable secret password as middle. The enable secret password is more secure and it supersedes the enable password if it is set. The enable secret password and the enable password cannot be the same on the 2950 switch.

Zenith(config)# line ?

First line number

console Primary terminal line

vty Virtual terminal

Zenith(config)# line vty ?

First line number

Zenith(config)# line vty 0 15

Zenith(config-line)# login

Zenith(config-line)# password alex

Zenith(config-line)# line con 0

Zenith(config-line)# login

Zenith(config-line)# password malouda

Zenith(config-line)# exit

Zenith(config)# exit

Zenith#

The line vty 0 15, login and password alex commands set the telnet password to alex and the line con 0, login, and password malouda commands sets the console password to malouda.

SETTING IP INFORMATION

You don't have to set any IP configuration on the switch to make it work. You can just plug it in. But there are two reasons we set IP address information on the switch.

To manage the switch via Telnet or other management software.

To configure the switch with different VLANs and other network functions.

Zenith(config)# int vlan 1

Zenith(config-if)# ip address 172.16.10.17 255.255.255.0

Zenith(config-if)# no shutdown

Zenith(config-if)# exit

Zenith(config)# ip default-gateway 172.16.10.1

Zenith(config)#

The IP address is set to 172.16.10.17 and the no shutdown command must be applied to enable the interface.

CONFIGURING INTERFACE DESCRIPTIONS

You can administratively set a name for each interface on the switches with the description command.

Zenith(config)# int fastethernet 0/ ?

FastEthernet Interface number.

Zenith(config)# int fastethernet 0/1

Zenith(config-if)# description Sales LAN

Zenith(config-if)# int f0/12

Zenith(config-if)# description Connection to Mail server

Zenith(config-if)# CNTL/Z
Zenith#

You can look at the descriptions at any time with either the show interface command or the show running-config command from the global configuration mode.

ERASING AND SAVING THE SWITCH CONFIGURATION
Zenith# copy running-config startup-config
Zenith# erase startup-config

The first command copies the configuration into the NVRAM (Non-volatile RAM) while the erase startup-config command erases the switch configuration.

Zenith# erase startup-config

Erasing the nvram filesystem will remove all files! Continue? [confirm] [Enter]

[OK]

Erase of nvram: complete

Zenith#

VIRTUAL LAN (VLAN)

A Virtual LAN (VLAN) is a logical grouping of network users and resources connected to administratively defined ports on a switch. When one create VLANs, one creates smaller broadcast domains within a switched internetwork by assigning different ports on the switch to different subnetworks. A VLAN is treated like its own subnet or broadcast domain, which means that frames broadcast onto the network are only switched between ports logically grouped within the same VLAN.
By default, no hosts in a specific VLAN can communicate with any other hosts that are members of another VLAN.
5.1 ADVANTAGES OF VLAN

A group of users needing security can be put into a VLAN so that no user outside the VLAN can communicate with them.

As a logical grouping of users by function, VLANs can be considered independent from their physical or geographical locations.

VLANs can enhance network security.

It can block broadcast storms caused by a faulty NIC (Network Interface Card) card.

VLANs increase the number of broadcast domains while decreasing their sizes.

VLAN MEMBERSHIP

VLANs are usually created by the administrator, who then assigns switch ports to each VLAN. Such a VLAN is called a static VLAN. If the administrator wants to do a little more work up front and assign all the host devices hardware addresses into a database, then the switch can be configured to assign VLANs dynamically whenever a host is plugged into a switch. This is called dynamic VLAN.

STATIC VLANs

Static VLANs are the usual way of creating VLANs, and they're also the most secure. The switch port that you assign a VLAN association to always maintain that association until an administrator manually changes that port assignment.

DYNAMIC VLANs

A dynamic VLAN determines a node's VLAN assignment automatically. Using intelligent management software, you can base assignment on hardware addresses, protocols, or even applications to create dynamic VLANs.

An example is the VLAN Management Policy Server (VMPS) service used to set up a database of MAC addresses that can be used for dynamic addressing of VLANs. A VMPS database maps MAC addresses to VLANs.

FRAME TAGGING

As frames are switched through the network, switches must be able to keep track of all the frames. Frames are handled differently according to the type of link they are traversing. The frame identification method uniquely assigns user defined ID to each frame. This is sometimes referred to as the "VLAN ID".

Each switch that the frame reaches must first identify the VLAN ID from the frame tag, and then it finds out what to do with the frame by looking at the information in the filter table. If the frame reaches a switch that has another trunked link, the frame will be forwarded out the trunk-link port.

Once the frame reaches an exit to an access link matching the frame's VLAN ID, the switch removes the VLAN identifier. This is so the destination device can receive the frame without having to understand their VLAN identification.

There are two different types of links in a switched environment, they are:
Access links: This type of link is only part of one VLAN. Any device attached to an access link is unaware of a VLAN membership; the device just assumes its part of a broadcast domain. Access link devices cannot communicate with devices outside their VLAN unless the packet is routed.
Trunk links: Trunk links can carry multiple VLANs. A trunk link is a 100 or 1000Mbps point to point link between two switches, between a switch and server. These carry the traffic of multiple VLANs from 1 to 1005 at a time. Trunking allows you to make a single port part of multiple VLANS at the same time. It also allows VLANs to span across multiple switches.

VLAN IDENTIFICATION METHODS

There are basically two ways of frame tagging.

Inter-Switch Link (ISL)

IEEE 802.1Q

The main purpose of ISL and 802.1Q frame tagging methods is to provide interswitch VLAN communication.

Inter-switch Link (ISL) Protocol: This is proprietary to Cisco switches, and it is used for fast Ethernet and gigabit Ethernet links only. ISL routing can be used on a switch port, router interfaces and server interface cards to trunk a server.

IEEE 802.1Q: Created by the IEEE as a standard method of frame tagging, it isn't Cisco proprietary so if you're trunking between a Cisco switched link and a different brand of switch; you have to use 802.1Q for the trunk link to work.

VLAN TRUNKING PROTOCOL (VTP)

This protocol was created by Cisco but it is not proprietary. The basic goals of VLAN Trunking protocol (VTP) are to manage all configured VLANs across a switched internetwork and to maintain consistency through the network. VTP allows an administrator to add, delete and rename VLANs on a switch, information that is then propagated to all other switches in the VTP domain.

Before one can get VTP to manage VLANs across the network, one has to create a VTP server. All switches sharing the same VLAN information must be in the same VTP domain.

One can use a VTP domain if there is more than one switch connected in a network, but if all the switches are in only one VLAN, there is no need to use VTP. VTP information is set between switches via trunk port.

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What is a Fiber Optic Pulling Eye?

Fiber optic pulling eye is also called cable pulling eye. It is a device that is fastened to a fiber cable. The hook can then be attached to the fiber pulling eye to pull the fiber cable through a innerduct, duct or small space.

Alternatively, it is possible to simply tie the pulling rope to the strength member in a fiber cable. This is enough for very simple pulls with very low resistance. But for conduit runs, this is a dangerous practice since the knot may catch along the path and fiber may be broken.
 
The cable pulling eye approach is a common and recommended practice for most fiber pulling jobs. Here are the general steps with this method.
 
1. Strip the cable to expose about 15cm of cable strength member only
2. Cover the strength members with epoxy glue
3. Fill the pipe section of a pulling eye with epoxy glue and fit it to the strength member. Allow the epoxy to set before starting pulling
4. Cover the end of the fiber cable with tape to ease the transition between strength member and cable. This protects the fiber cable and also stops ingress of dirt or water
5. For long cable runs, use intermediate pulling points where the cable is pulled through and coiled up in a figure "8" pattern on the ground and then fed into the next conduit section
6. At intermediate pulling points, reapply cable pulling lubricant to the cable before pulling through the next conduit section
 
Another popular method of attaching a pulling rope to a fiber optic cable is the "Chinese Basket" or "Kellems Grip". This is most effective with larger diameter cables.

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The Importance of a Modem

Modem means modulator and demodulator. It is a gadget that you use to transmit date and to receive data as well via a channel for communication. These channels can be a cable, telephone line and an optic fiber.

1. The first answer to the question, why is a modem needed is because we need a converter so data can be transferred to the analog system of the telephone. Today we can also change data that is digital to analog mode. The signal is then changed into digital by the modem through demodulation. This is the simple explanation on the processes that takes place in a modem. Other processes that take place in a modem are error corrections, detection of errors, compressing data and encryption.

2. The second answer to the question, why is a modem needed is for giving higher quality and faster transfer of data. There are fast modems that will remove the problem of most companies about time delays. They also need this to give real-time customer support. It also gives fast communication which is needed by many people.

3. The third answer to the question, why is a modem needed is for giving good quality of graphics for bigger applications. This is especially needed for applications with programs like Java. A fast modem is also needed for creating applications for multimedia as well as games that are three dimensional.

4. The fourth answer to the question, why is a modem needed is for creating the local area network for homes or offices. Today this is one of the most inexpensive ways to connect one computer to the other. This facilitates faster communication like in a hospital where the patients and the medical staff would have quicker access on the health records. For the entertainment industry this is needed to provide clearer pictures and sounds like the HDTV.

5. A modem is also needed because there are still remote places in the world that doctors, lawyers and government officials do not frequently go to. They can only be reached by other people via telecommunications which can be facilitated by having a modem and a computer.

6. Another reason why a modem is needed is for facilitating the fast growth of the economy of a country. Most businesses today operate via online communication. You can easily close a business deal via the Internet. People can also do online shopping which became a trend these days because of the modem.

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