CHAPTER 1INTRODUCTION 1.1 Optical fiberFiber optics (optical fibers) are long, thin strands of very pure glass about the diameter of a human hair. They are arranged in bundles called optical cables and used to transmit light signals over long distances. Fiber-optic communicationis a method of transmitting information from one place to another by sending pulses oflightthrough an optical fiber. The light forms anelectromagneticcarrier wavethat ismodulatedto carry information. First developed in the 1970s, fiber-opticcommunication systemshave revolutionized thetelecommunicationsindustry and have played a major role in the advent of the Information Age. Because of itsadvantages over electrical transmission, optical fibers have largely replaced copper wire communications in core networksin thedeveloped world. Optical fiber is used by many telecommunications companies to transmit telephone signals, Internet communication, and cable television signals. Researchers atBell Labshave reached internet speeds of over 100petabitsper second using fiber-optic communication.The process of communicating using fiber-optics involves the following basic steps: Creating the optical signal involving the use of a transmitter, relaying the signal along the fiber, ensuring that the signal does not become too distorted or weak, receiving the optical signal, and converting it into anelectrical signal.

Fig.1.1.Optical fiber

1.2 History of optical fiberPrior to the introduction of optical fiber the information was transmitted through electromagnetic wavesFiber optics really developed in 1950s with the work of Hopkins and Narendra Singh Kapany in UK and Van Heel in HollandActual invention took place in 1960 after the development of semiconductor laser and LED.In 1880Alexander Graham Belland his assistantCharles Sumner Taintercreated a very early precursor to fiber-optic communications, thePhotophone, at Bell's newly establishedVolta LaboratoryinWashington, D.C.Bell considered it his most important invention. The device allowed for thetransmissionof sound on a beam of light. On June 3, 1880, Bell conducted the world's first wirelesstelephonetransmission between two buildings, some 213 meters apart.[2][3]Due to its use of an atmospheric transmission medium, the Photophone would not prove practical until advances in laser and optical fiber technologies permitted the secure transport of light. The Photophone's first practical use came in military communication systems many decades later.In 1966Charles K. KaoandGeorge Hockhamproposed optical fibers at STC Laboratories (STL) atHarlow, England, when they showed that the losses of 1000 dB/km in existing glass (compared to 5-10 dB/km in coaxial cable) was due to contaminants, which could potentially be removed.Optical fiber was successfully developed in 1970 byCorning Glass Works, with attenuation low enough for communication purposes (about 20dB/km), and at the same time GaAssemiconductor laserswere developed that were compact and therefore suitable for transmitting light through fiber optic cables for long distances.After a period of research starting from 1975, the first commercial fiber-optic communications system was developed, which operated at a wavelength around 0.8m and used GaAs semiconductor lasers. This first-generation system operated at a bit rate of 45Mbpswith repeater spacing of up to 10km. Soon on 22 April 1977, General Telephone and Electronics sent the first live telephone traffic through fiber optics at a 6 Mbit/s throughput in Long Beach, California.The first wide area network fibre optic cable system in the world seems to have been installed by Rediffusion in Hastings, East Sussex, UK in 1978. The cables were placed in ducting throughout the town, and had over 1000 subscribers. They were used at that time for the transmission of television channels,not available because of local reception problems. The system is still in place, but disused. The second generation of fiber-optic communication was developed for commercial use in the early 1980s, operated at 1.3m, and used InGaAsP semiconductor lasers. These early systems were initially limited by multimode fiber dispersion, and in 1981 thesingle-mode fiberwas revealed to greatly improve system performance, however practical connectors capable of working with single mode fiber proved difficult to develop. By 1987, these systems were operating at bit rates of up to 1.7Gb/s with repeater spacing up to 50km.The firsttransatlantic telephone cableto use optical fiber wasTAT-8, based on Desurvire optimized laser amplification technology. It went into operation in 1988.Third-generation fiber-optic systems operated at 1.55m and had losses of about 0.2dB/km. This development was spurred by the discovery ofIndium gallium arsenideand the development of the Indium Gallium Arsenide photodiode by Pearsall. Engineers overcame earlier difficulties withpulse-spreadingat that wavelength using conventional InGaAsP semiconductor lasers. Scientists overcame this difficulty by usingdispersion-shifted fibersdesigned to have minimal dispersion at 1.55m or by limiting the laser spectrum to a singlelongitudinal mode. These developments eventually allowed third-generation systems to operate commercially at 2.5 Gbit/s with repeater spacing in excess of 100km.The fourth generation of fiber-optic communication systems usedoptical amplificationto reduce the need for repeaters andwavelength-division multiplexingto increasedata capacity. These two improvements caused a revolution that resulted in the doubling of system capacity every 6 months starting in 1992 until a bit rate of 10Tb/s was reached by 2001. In 2006 a bit-rate of 14 Tbit/s was reached over a single 160km line using optical amplifiers.[4]The focus of development for the fifth generation of fiber-optic communications is on extending the wavelength range over which aWDMsystem can operate. The conventional wavelength window, known as the C band, covers the wavelength range 1.53-1.57m, anddry fiberhas a low-loss window promising an extension of that range to 1.30-1.65m. Other developments include the concept of "optical solitons, " pulses that preserve their shape by counteracting the effects of dispersion with thenonlinear effectsof the fiber by using pulses of a specific shape.In the late 1990s through 2000, industry promoters, and research companies such as KMI, and RHK predicted massive increases in demand for communications bandwidth due to increased use of theInternet, and commercialization of various bandwidth-intensive consumer services, such asvideo on demand.Internet protocoldata traffic was increasing exponentially, at a faster rate than integrated circuit complexity had increased underMoore's Law. From the bust of the dot-com bubble through 2006, however, the main trend in the industry has beenconsolidationof firms andoffshoringof manufacturing to reduce costs. Companies such asVerizonandAT&Thave taken advantage of fiber-optic communications to deliver a variety of high-throughput data and broadband services to consumers' homes.

1.3 Parts of Optical Fiber Core Cladding Buffer Coating

Fig.1.2.Parts of optical fiber

CHAPTER 2How Does an Optical Fiber Transmit Light?

Fig.2.1 Transmission of light in O.F.C.

2.1 Physics of total internal reflection The angle of the light is always greater than the critical angle Cladding does not absorb any light from the core The extent that the signal degrades depends upon the purity of the glass and the wavelength of the transmitted light

Fig.2.2 Total internal reflection in OFC

2.2 Fiber Optics Data Links

Fig.2.3 Fiber Optic Link

CHAPTER 3SPLICING

3.1 Introduction to SplicingSplices are permanent connection between two fibres. The splicing involves cutting of the edges of the two fibres to be spliced. This cut has to be carefully made to have a smooth surface and is generally achieved by a special cutting tool. The two ends, thus, prepared are then brought together and made to butt against each other. The fibres are then fixed permanently and reinforced. The fixing process can be achieved in a number of ways. It could be mechanically fixed permanently through uses of epoxies or through fusion. There are two types of fiber splicing Mechanical splicing and Fusion splicing.

Mechanical splicing doesnt physically fuse two optical fibers together, rather two fibers are held butt-to-butt inside a sleeve with some mechanical mechanism. You will get worse insertion loss and back reflection in mechanical splices than in fusion splices (the second type we are introducing below).Mechanical splicing is mostly used for emergency repairs and fiber testing. You can check out some mechanical splice products here.

Figure 3.1: Mechanical splice

The second type splicing is called fusion splicing. In fusion splicing, two fibers are literally welded (fused) together by an electric arc. Fusion splicing is the most widely used method of splicing as it provides for the lowest insertion loss and virtually no back reflection.

Fusion splicing provides the most reliable joint between two fibers. Fusion splicing is done by an automatic machine called fusion splicer (fusion splicing machines).

Figure 3.2: Fusion splice

3.2 Splice LossesSplice losses can be divided into two categories as shown in Table. Extrinsic and intrinsic splice loss factors

3.3 Splicing Methods The following three types are widely used: 1. Adhesive bonding or Glue splicing. 2. Mechanical splicing. 3. Fusion splicing. 1. Adhesive Bonding or Glue Splicing

This is the oldest splicing technique used in fibre splicing. After fibre end preparation, it is axially aligned in a precision Vgroove. Cylindrical rods or other kind of reference surfaces are used for alignment. During the alignment of fibre end, a small amount of adhesive or glue of same refractive index as the core material is set between and around the fibre ends. A two component epoxy or an UV curable adhesive is used as the bonding agent.The splice loss of this type of joint is same or less than fusion splices. But fusion splicing technique is more reliable, so at present this technique is very rarely used.

2. Mechanical Splicing

This splicing is mainly used for temporary splicing in case of emergency repairing. This method is also convenient to connect measuring instruments to bare fibres for taking various measurements. The mechanical splices consists of 4 basic components : (i) An alignment surface for mating fibre ends. (ii) A retainer. (iii) An index matching material. (i) A protective housing.

A very good mechanical splice for M.M. fibres can have an optical performance good as fusion spliced fibre or glue spliced. But in case of single mode fibre, this type of splice cannot have stability of loss.

3. Fusion Splicing

The fusion splicing technique is the most popular technique used for achieving low splice losses. The fusion can be achieved either through electrical arc or through gas flame. The process involves cutting of the fibres and fixing them in micropositioners the fusion splicing machine. The fibres are then aligned either manually or automatically core aligning (in case of S.M. fibre) process. Afterwards, the operation that takes place involve withdrawal of the fibres to a specified distance, preheating the fibre ends through electric arc and bringing together of the fibre ends in a position and splicing through high temperature fusion. If proper care is taken and splicing is done strictly as per schedule, then the splicing loss can be minimized as low as 0.01 dB/joint. After fusion splicing, the splicing joint should be provided with a proper protector to have following protections: (a) Mechanical protection (b) Protection from moisture. Sometimes the two types of protection are combined. Coating with Epoxy resins protects against moisture and also provides mechanical strength at the joint. Nowadays the heat shrinkable tubes are most widely used, which are fixed on the joints by the fusion tools.3.4 Principle of fusion splice technique : It is most widely used method for splicing optical fiber. There are a number of fusion welding machines manufactured by different companies, some of them are fully automatic and controlled by a microprocessor and some are partly automatic and manually controlled. In some cases, the fiber ends & the fusion process can be seen on a TV-monitor screen.

The process can be sub-divided into the following three steps :(a) Axial alignment. (b) Perfusion & (c) Actual fusion welding.

In case of the old machines the axial alignment is done manually by manipulating a number of knobs and is observed with the help of a high power microscope. This is normally followed in case of multimode fiber. In case of modern machines, pre-aligned, V-grooves are provided a finer adjustment is done, if necessary. For single mode fiber, other techniques are followed. The best one is fully automatic core alignment method which is now days used. After alignment is done, the ends of the fiber are fire polished by an electric arc and this method is called pre-fusion. During this process, the fiber ends are kept separated at a distance, after this they are brought closer and the process is called as fiber end feedings. This feeding process is continued during actual fusion by electric arc to prevent a reduced section at the point of welding. The process of perfusion, fiber ends feed and actual fusion are critical to a good weld and are frequently automatically controlled by the fusion machine. The fusion time of single mode fiber is less than that the multimode fiber. The Introduction of single mode fiber for use in long haul network, brought with it different fiber construction and cable design, from that of multimode cables. The design of the cable, the brittleness of the fiber and the requirement of accurately aligning the single mode fiber cores, required splicing techniques different to those used for multimode fiber, where aligning of the cladding is done. Due to this sophisticated splicing machines were developed.

The main functions of the above are: (1) Auto active alignment of the core. (2) Auto arc fusion. (3) Video display of the entire process.(4) Indication of the estimated loss at the slice. In this core profile alignment system (CPA), the two fiber ends to be spliced are cleaved and then clamped in accurately machined V- grooves. A video image proceeding technique is used to detect the boundary between the core and cladding glasses in the fibers on each side of the splice point. The core boundaries in the fibers and aligned in the horizontal and vertical plane by microprocessor controlled micropositioners. When the optimum alignment is achieved, the fibers are automatically fused under the micro-processor control. The machine then measures the radial and angular offsets of the fibers and uses these figures to calculate a splice loss estimated, which is used only as a guidance. The operator of the machine observes the alignment and fusion processes on a video screen showing horizontal and vertical projection of the fibres and then decides the quality of the splice.

3.5 Requirement of a good spliceFollowing are the requirements of a good splice. (i) Low loss. (ii) Stability of loss (iii) Reliability. (iv) Ease of reopening. (v) Low cost. Considering all the above facts, suitable methods of splicing should be selected. The Following are the common steps in every splicing method. (A) Fibre and preparation: (I) Fibre stripping. (II) Fibre cleaning. (III) Fibre cutting

(B) Axial alignment.

(C) Actual splicing of two fibre ends.

Figure 3.3: Arc Method in Fusion Splice

3.6 FIBER OPTIC CABLE SPLICING PROCEDURE (HOW TO SPLICE FIBER OPTIC CABLE)

1. Strip fiber cable jacket. Strip back about 1 meters of fiber cable jacket to expose the fiber loose tubes or tight buffered fibers. Use cable rip cord to cut through the fiber jacket. Then carefully peel back the jacket and expose the insides. Cut off the excess jacket. Clean off all cable gel with cable gel remover. Separate the fiber loose tubes and buffers by carefully cutting away any yarn or sheath. Leave enough of the strength member to properly secure the cable in the splice enclose. 2. Strip fiber tubes. For a loose tube fiber cable, strip away about 0.9 meters of fiber tube using a buffer tube stripper and expose the individual fibers. 3. Clean cable gel. Carefully clean all fibers in the loose tube of any filling gel with cable gel remover. 4. Secure cable tubes. Secure the end of the loose tube to the splice tray and lay out cleaned and separated fibers on the table. Strip and clean the other cable tubes fiber that is to be spliced, and secure to the splice tray. 5. Strip first splicing fiber. Hold the first splicing fiber and remove the 250um fiber coating to expose 5cm of 125um bare fiber cladding with fiber coating stripper tool. For tight buffered fibers, remove 5cm of 900um tight buffer first with a buffer stripping tool, and then remove the 5cm of 250um coating.

6. Place the fusion splice protection sleeve. Put a fusion splice protection sleeve onto the fiber being spliced. 7. Clean the bare fiber. Carefully clean the stripped bare fiber with lint-free wipes soaked in isopropyl alcohol. After cleaning, prevent the fiber from touching anything. 8. Fiber cleaving. With a high precision fiber cleaver, cleave the fiber to a specified length according to your fusion splicers manual. 9. Prepare second fiber being spliced. Strip, clean and cleave the other fiber to be spliced. 10. Fusion splicing. Place both fibers in the fusion splicer and do the fusion splice according to its manual. 11. Heat shrinks the fusion splice protection sleeve. Slide the fusion splice protection sleeve on the joint and put it into the heat shrink oven, and press the heat button. 12. Place splice into splice tray. Carefully place the finished splice into the splice tray and loop excess fiber around its guides. Ensure that the fibers minimum bending radius is not compromised. 13. Perform OTDR test. Perform a OTDR test of the splice and redo the splice if necessary. 14. Close the splice tray. After all fibers have been spliced, carefully close the splice tray and place it into the splice enclosure. 15. Bidirectional OTDR test (or power meter test). Test the splices with an OTDR or power meter from both directions. 16. Mount the splice enclosure. Close and mount the splice enclosure if all splices meet the specifications. CAUTIONAvoid places with too much dust or dirt. Dirt or dust that can accumulate in the fusion splicer causing short circuits or insufficient cooling, which may lead to splicer malfunction or deterioration, resulting in fire or electric shock. To reduce the risk of electric shock, do not plug/unplug the power cord or remove the battery with wet hands. Disconnect the power cord by grasping the plug, not the cord. The battery's optimum charging temperature range is 0 to 45C. Whenever possible, place the charger in a location that is within this temperature range. Do not charge the battery at extremely low temperature (below 0C). Doing so may lead to deterioration in performance and battery leakage. If you are not going to use the splicer for a while, remove the battery before storing it. Not doing so will shorten a battery life. Only use 99% pure alcohol to clean the splicer. To prevent malfunction and damage, do not use any other kind of chemicals. The heating plate of the heat shrink oven may be hot during and after heating. Do not touch it directly. Do not operate the splicer in rain. Doing so may cause the battery or AC power supply to be short-circuited.

CHAPTER 4Fiber-Optic ApplicationsThe use and demand for optical fiber has grown tremendously and optical-fiber applications are numerous. Telecommunication applications are widespread, ranging from global networks to desktop computers. These involve the transmission of voice, data, or video over distances of less than a meter to hundreds of kilometers, using one of a few standard fiber designs in one of several cable designs. Fiber Optic Interconnects Interconnections are one of the largest and most widely used areas for fiber optic cables and assemblies. An interconnect is defined as the physical connection of two or more fixtures through which communication is possible. Interconnects range from simple, simplex patch cords to multi-channel distribution and backbone cables and virtually everything in between. Most interconnects are used for smaller, localized network or system structures, linking similar machines, complimentary devices, and/or data communications from one system to another. Fiber Optic Networking With the increasing bandwidth requirements associated with broadband services, service providers and network operators are expanding and extending fiber optics further down line to accommodate present and future requirements. This network extension and expansion requires multiple fiber optic connectivity products in a myriad of forms. Trunk cables, distribution cables, high-density interconnect cables, and standard patch cords are just a few of the many types of products.

Gigabit Ethernet Gigabit Ethernet solutions have become a necessity with the accelerating growth of LAN traffic, pushing network administrators to look for higher speed network technologies to meet the demand for more bandwidth. While most copper systems will support Gigabit Ethernet, fiber optics provide a much higher degree of flexibly and future bandwidth/speed expansion as opposed to its copper counterparts. Generally, copper will support Gigabit and multi-gig transmission rates, but only for very short distances. Copper is affected by EMI (electromagnetic interference) and RFI (radio frequency interference). Fiber opics will support Gigabit and multi-gig transmission for both short and long distances, with immunity to EMI and RFI, making fiber a more suitable solution for a number of applications. Gigabit Ethernet applications supported by fiber optics are now transmitting signal reliably at 10Gbps, up to 10,000 meters using single mode systems, and well over that for Gigabit and multi-gig transmission rates. With multimode systems, fiber optics will push 10Gbps transmission between 26 and 300 meters, depending on the fiber type and core size. Data Transfer Tests For testing applications, optical or electrical loopbacks are used to verify the operational reliability of the device under test. With both optical and electrical loopbacks, the signal generated by the device under test is looped from the transmit (Tx) side of an active component back to the receive (Rx) port of the same component. Fiber Optics for Data Storage EquipmentFiber optic connectivity offers very high bandwidth over extended distances making optical communication an ideal conduit for device-to-device connections, enabling faster, simultaneous information access from across the room or across the country. While some data storage devices use copper connections and cabling for device-to-device connections, more data storage administrators are replacing copper ports with optical ports to improve performance and ensure these devices can support ever increasing bandwidth requirements now and in the future. Premise Networks Premise network is defined as the transmission network (LAN) inside the users' building or group of buildings that connects the various types of voice and data communications devices to each other and to the outside world. Carrier Networks Carrier networks are defined as a network, or series of networks, providing connectivity to cities, towns, or other entities on a large scale. Communications service providers utilize these networks to distribute very large amounts of bandwidth over long distances, providing the communication necessary to support premise networks and central office, and all other communications and broadband services offered at the end. Outside Plant Outside plant is defined as all the cables, conduits, ducts, poles, towers, repeaters, repeater huts, and other equipment located between a demarcation point in a switching facility and a demarcation point in another switching facility or customer premises. Simply put, this is the portion of your network that resides outside your facilities, connecting you with the outside world. Most outside plant applications require cabling, enclosures, optical nodes, or distribution points to withstand any number of adverse circumstances directly related to its surroundings. Outside plant products are designed to perform the same functionality as their industry standard counterparts, with additional protection or ruggedization, greatly reducing the opportunity for failure while in service. Typically these products are designed using specialized jacketing, cases, and/or distribution methods to ensure durability. Generally, companies use these products for direct burial cabling and enclosures, aerial cabling, water and chemical proof environmental connections, and crush-resistant/proof connectivity requirements. Broadcast Fiber Optics The broadcast fiber optics are designed to provide multiple channel, high-bandwidth links and, in some cases, power (electrical) connections to and from cameras, trucks, and satellite links. With the increasing demand for HDTV programming, broadcasters are implementing more fiber to support HDTV signal capture and transport at live sports, music, and entertainment events. Fiber is also rapidly becoming the data transmission method of choice for stadiums, arenas, and venues allowing these facilities to supply high-definition content for HDTV, video-on-demand, and broadband networks. Automotive Fiber OpticsFiber optic technology is becoming the medium of choice for a variety of automotive applications. With its unique characteristics, fiber optics are a naturally ideal choice for lighting, communications, and sensing requirements. Automobile manufacturers are using fiber for lighting applications for several reasons. First and foremost, fiber transmits cold light, making it a safe alternative to traditional sealed beam or halogen lighting. Apart from the safety advantage, the light source is easily accessible and offers much more in creative freedom of design. Fiber also allows for light source and output location separation, creating high performance lighting options with reduced physical space requirements for difficult and restricted access locations.

Fiber Optics for Sensing Fiber optics for sensing applications are used to communicate with a sensor device, or use a fiber as the sensor itself, to conduct continuous monitoring of physical, chemical, and biological changes in the subject or object of study. Fiber optic sensing is a key component to improving industrial processes, quality control systems, medical diagnostics, and preventing and controlling general process abnormalities. Fiber optics used for these applications provide very acute sensitivity and data collection versatility, while allowing for a wide range of specialized application uses. Fiber Optics for Oil & Gas Fiber optics are used for a number of applications in the oil and gas markets. These markets require very specific cabling and connectivity requirements to ensure the utmost in safety, productivity, and harsh environment durability. As producers of one of the most widely used consumables, oil and gas companies are rapidly expanding operations to support the increasing global demand for petroleum products. As part of this deployment, these companies are installing fiber optics to leverage the advantages offered by fiber, improving the overall performance and accuracy of their operations. HDTV HDTV (high definition television) is the broadcasting of a higher resolution format than possible with traditional analog television broadcasting. A form of digital television, HDTV is a very bandwidth intensive application requiring maximum allowable speed and data volume transfer. Originating with HD camera and video capture/processing equipment, television networks, service providers, and production companies are utilizing fiber optics as the support and distribution structure all the way to the subscriber premises. Data Transmission Fiber OpticsData transmission fiber optics, simply put, is the sending and receiving of data from point-to-point via a network, thus the fundamental function of all fiber systems from small to large. Data transmission requirements range from very simple cables connecting servers or storage arrays inside a network or telecommunications system, to large multi-fiber distribution cables supporting intra-building connectivity and beyond. Fiber Optic Imaging Imaging applications require individual fibers to be aligned, fused, and bundled to function correctly as an image guide. Bundling is necessary as a single fiber optic cable is only capable of reproducing a single color of varying intensity, based on what it received from the source or subject area. By bundling several, in some cases thousands of identical individual fibers, an image guide or coherent bundle relies on each fiber to focus on reproducing a single color, but collectively the bundle reproduces the target subject exactly.

4.1 ADVANTAGES OF OPTICAL FIBER COMMUNICATION Fiber Optics has the following advantages: Wider bandwidth: The information carrying capacity of a transmission system is directly proportional to the carrier frequency of the transmitted signals. The optical carrier frequency is in the range 1013 to 1015 Hz while the radio wave frequency is about 106 Hzand the microwave frequency is about 1010 Hz. Thus the optical fiber yields greater transmission bandwidth than the conventional communication systems and the data rate or number of bits per second is increased to a greater extent in the optical fiber communication system

Low transmission loss: Due to the usage of the ultra low loss fibers and the erbium doped silica fibers as optical amplifiers, one can achieve almost lossless transmission. In the modern optical fiber telecommunication systems, the fibers having a transmission loss of 0.002dB/km are used. Further, using erbium doped silica fibers over a short length in the transmission path at selective points; appropriate optical amplification can be achieved. Thus the repeater spacing is more than 100 km. Since the amplification is done in the optical domain itself, the distortion produced during the strengthening of the signal is almost negligible. Dielectric waveguide: Optical fibers are made from silica which is an electrical insulator. Therefore they do not pickup any electromagnetic wave or any high current lightning. It is also suitable in explosive environments. Further the optical fibers are not affected by any interference originating from power cables, railway power lines and radio waves. There is no cross talk between the fibers even though there are so many fibers in a cable because of the absence of optical interference between the fibers. Signal security: The transmitted signal through the fibers does not radiate. Further the signal cannot be tapped from a fiber in an easy manner. Therefore optical fiber communication provides hundred per cent signal security. Small size and weight:Fiber optic cables are developed with small radii, and they are flexible, compact and lightweight. The fiber cables can be bent or twisted without damage. Further, the optical fiber cables are superior to the copper cables in terms of storage, handling, installation and transportation, maintaining comparable strength and durability.

4.2 Disadvantages Optical Fibre cables are expensive to install. The termination of a fiber optics cable is complex and requires special tools. They are more fragile than coaxial cable.

Some manufacturers of optical fibers

Furukawa Fujikura LG Cables Corning Philips-Fitel Pirelli TTL Sterlite Cables

Fig 4.1 Some Manufacturers of optical Fiber cables

Chapter 5Innovations in Optical FiberCommunication5.1 Fiber Optics in Data TransmissionInnovations inoptical fiber technologyare revolutionizing world Communications. Newly developed fiber amplifiers allow for direct transmission of high-speed signals over transcontinental distances without the need for electronic regeneration. Optical fibers find new applications in data processing. The impact of fiber materials, devices, and systems on communications in the coming decades will create an abundance of primary literature and the need for up-to-date reviews.5.2 Fiber Optic Innovation Could Hold Key To Bandwidth BreakthroughA new design for fiber-optic cables puts a literal twist on data transmissions, an innovation that could lead to Internet connections with dramatically bigger bandwidth capacity.Cables might seem invisible in the age of Wi-Fi, but theyre still essential to communication. Even though your smartphone or laptop connects to the Internet wirelessly, it still relies on fiber optics to transmit your tweets and texts long distances. These fibers are, essentially, light pipes.Since the 1990s, weve increased our bandwidth capacity by encoding data in different colors of light, but now that strategy by itself is starting to reach the limit of its usefulness.What happened is that we ran out of colors to add, Boston University engineer Siddharth Ramachandran explained in a phone interview.Ramachandran, along with colleagues from the University of Southern California, describe a new dimension for fiber-optic transmission in a paper appearing in thejournal Science this week. Their new design can transmit data through a 1 kilometer (.62 mile) long cable at a rate of 1.6 terabits per second -- the equivalent of eight Blu-Ray DVDs every second.

Figure 5.1: High Data Transfer through OFC

5.3 Fiber optics for high data transferResearches has been done to create a fiber super cable that had the capacity to transmit seven separate light pulses at once.In March, Dayou Qian, of NEC, reported a run in which he was able to transmit data at an unprecedented rate of 101.7 terabits per second across a distance of 165 kilometers. This was achieved by sending the information along as 370 separate lasers that was received as one light pulse at the other end.While in Japan, Jun Sakaguchi of the National Institute of Information and Communications Technology in Tokyo one-upped that mark when his research team delivered data at 109 terabits per second.

5.4 ConclusionThe need for fast method of data transfer has become very important in thismodern world. Innovations inoptical fiber technologyare revolutionizing world Communications. The impact of fiber materials, devices, and systems on communications in the coming decades will create an abundance of primary literature and the need for up-to-date reviews.Through increased bandwidth we can transfer large amount of data in less time.Data clarity is another important aspect which is obtained in optical fibre cables.

APPENDICES: Fiber optic Connectors

Fig .a.1 D4 Connector

Connectors are vital elements in the Fiber Optics Technology. Connectors can be defined as a remittable means of arranging transfer of optical energy from one fiber optic component to another in an optical fiber system. SC Connector

Fig.a.2 A SC ConnectorAlthough the mechanical design varies a lot among different connector types, the most common elements in a fiber connector can be summarized in the following picture. The example shown is a SC connector which was developed by NTT (Nippon Telegraph and Telephone) of Japan.Optical Time Domain ReflectometerAn OTDR sends short pulses of light into a fiber. Light scattering occurs in the fiber due to discontinuities such as connectors, splices, bends, and faults. An OTDR then detects and analyzes the backscattered signals. The signal strength is measured for specific intervals of time and is used to characterize events.

REFERENCES 1] www.learntelecom.bsnl.co.in 2] www.wikipedia.org/wiki/opticalfibre3] Optical Fibre communication by Keiser4] Website of ITU-T5] An introduction to fiber optics - Ajoy K. Ghatak, K. Thyagarajan 6] http://www.fiber-optics.info 7] www.arcelect.com 8] http://www.flukenetworks.com/expertise/learn-about/otdr 9] www.fiberoptics4sale.com/Merchant2/fiber-optic-splicing-tutorial.php 10] www.advantra.net/sample1.pdf

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