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Introduction to Telecommunication. Dr. Adeel Akram Telecom Engineering Department, UET Taxila. THE PRESENTATION. What this presentation is about?
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Introduction to Telecommunication Dr. Adeel Akram Telecom Engineering Department, UET Taxila
THE PRESENTATION What this presentation is about? This presentation is about giving a broad idea about the concepts of Optical Communication and Optical Fiber (OF) Cables, (OPGW, Lashed cables, ADSS, Under Ground & Duct Cables ) without going into the deep technicalities. So that as and when OF is being discussed the person who has attended this presentation is able to understand and follow the discussion. • Brief Flow of the Presentation. • What are Optical Fibers? • Advantages / Disadvantages of OF…. • Various Types of OF Cables. Their Construction , Specifications etc… • Some Test Equipments & Instruments used in OF Communications.
Need for Fiber Optical Communication • Increase of the bandwidth and decreases of the cost per transmitted bit for optical communication systems during the 1990‘s. Ref.: S. Kartalopoulos, WDWM Netorsk, Devices and Technology
Need for Fiber Optical Communication Bit-rate distance product (BL) for different generations of optical communication systems. Ref.: G.P. Agrawal, Fiber-optic Communication systems The increase of the capacity-distance product can be explained by the four major innovations.
Evolution of Light wave systems 1st Generation: The development of low-loss fibers and semiconductor lasers (GaAs) in the 1970‘s. A Gallium Aresenide (GaAs) laser operates at a wavelength of 0.8μm. The optical communication systems allowed a bit rate of 45Mbit/s and repeater spacing of 10km. Example of a laser diode. (Ref.: Infineon)
Evolution of Lightwave systems 2nd Generation: The repeater spacing could be increased by operating the lightwave system at 1.3μm. The attenuation of the optical fiber drops from 2-3dB/km at 0.8μm down to 0.4dB/km at 1.3μm. Silica fibers have a local minima at 1.3μm.
2nd Generation: The transition from 0.8μm to 1.3μm lead to the 2nd Generation of lightwave systems. The bit rate-distance product can be further increased by using single mode fibers instead of multi-mode fibers. Single mode fibers have a distinctly lower dispersion than multi mode fibers. Lasers are needed which emit light at 1.3 μm.
3rd Generation: Silica fibers have an absolute minima at 1.55μm. The attenuation of a fiber is reduced to 0.2dB/km. Dispersion at a wavelength of 1.55μm complicates the realization of lightwave systems. The dispersion could be overcome by a dispersion-shifted fibers and by the use of lasers, which operate only at single longitudinal modes. A bit rate of 4Gbit/s over a distance of 100km was transmitted in the mid 1980‘s. Traditional long distance single channel fiber transmission system. Ref.: H. J.R. Dutton, Understanding optical communications
3rd Generation: The major disadvantage of the 3rd Generation optical communication system is the fact that the signals are regenerated by electrical means. The optical signal is transferred to an electrical signal, the signal is regenerated and amplified before the signal is again transferred to an optical fiber. 4thGeneration: The development of the optical amplifier lead to the 4th Generation of optical communication systems. Schematic sketch of an erbium-doped fiber amplifier (EDFA). Ref.: S.V. Kartalopoulos, Introduction to DWDM Technology
Evolution of Lightwave systems State of the Art optical communication system: Dense Wavelength Division Multiplex (DWDM) in combination of optical amplifiers. The capacity of optical communication systems doubles every 6 months. Bit rates of 10Tbit/s were realized by 2001. Ref.: S. Kartalopoulos, WDWM Networks, Devices and Technology
Optical Fiber & OF Cables
WHAT ARE OPTICAL FIBERS ? Optical Fibers are thins long (km) strands of ultra pure glass (silica) or plastic that can to transmit light from one end to another without much attenuation or loss. The glass used to make Optical Fibers is so pure that if the Pacific Ocean was filled with this glass then we would be able to see the ocean bottom form the surface….!!!! This is to be believed as repeater distances on long haul routes for optical fibers vary from 50 to 150 km. Q.) And how deep is the Pacific ocean? Ans) At the deepest point called the Marina Trench, The pacific ocean is all of just 13km deep…..!!!!!
Working of Optical fibers? The light source (LAZER) at the transmitting (Tx) end is modulated by the electrical signal and this modulated light energy is fed into the Optical Fiber. At the receiving end (Rx) this light energy is made incident on photo-sensors which convert this light signal back to electrical signal.
Why Optical Fibers ? As mans need and hunger for communication increased, the amount of bandwidth required increased exponentially. Initially we used smoke signals, then horse riders for communicating. But these ways were way to slow and had very little bandwidth or data caring capacity. Then came the telephone and telegraph that used copper wires for communication. But soon demand out striped the capacity and capability of copper wires and data transport got added to voice communication. Then came Coaxial copper cables, VHF and UHF Radios, Satellite but demand still outstripped the supply. It was not until Optical Fibers came on the scene that large amount of communication bandwidth became economically and easily available to everyone. As an example 50,000 voice / data circuit copper cable is massive in size and very expensive, while a single Optical Fiber, the diameter of human hair, can carry 5,00,000 circuits of voice and data. This capacity is increasing day by day as supporting electronics is developing. In itself the capacity of Optical Fibers is limitless.
ADVANTAGES OF OPTICAL FIBERS • VERY HIGH INFORMATION CARRING CAPACITY. • LESS ATTENUATION (order of 0.2 db/km) • SMALL IN DIAMETER AND SIZE & LIGHT WEIGHT • LOW COST AS COMPARED TO COPPER (as glass is made from sand..the raw material used to make OF is free….) • GREATER SAFETY AND IMMUNE TO EMI & RFI, MOISTURE & COROSSION • FLEXIBLE AND EASY TO INSTALL IN TIGHT CONDUICTS • ZERO RESALE VALUE (so theft is less) • IS DILECTRIC IN NATURE SO CAN BE LAID IN ELECTICALLY SENSITIVE SURROUNDINGS • DIFFICULT TO TAP FIBERS, SO SECURE • NO CROSS TALK AND DISTURBANCES
DISADVANTAGES OF OPTICAL FIBERS… • The terminating equipment is still costly as compared to copper equipment. • OF is delicate so has to be handled carefully. • Last mile is still not totally fiberised due to costly subscriber premises equipment. • Communication is not totally in optical domain, so repeated electric –optical – electrical conversion is needed. • Optical amplifiers, splitters, MUX-DEMUX are still in development stages. • Tapping is not possible. Specialized equipment is needed to tap a fiber. • Optical fiber splicing is a specialized technique and needs expertly trained manpower. • The splicing and testing equipments are very expensive as compared to copper equipments.
APPLICATIONS OF OPTICAL FIBERS… • LONG DISTANCE COMMUNICATION BACKBONES • INTER-EXCHANGE JUNCTIONS • VIDEO TRANSMISSION • BROADBAND SERVICES • COMPUTER DATA COMMUNICATION (LAN, WAN etc..) • HIGH EMI AREAS • MILITARY APPLICATION • NON-COMMUNICATION APPLICATIONS (sensors etc…)
SPECIFICATIONS OF OPTICAL FIBERS… MULTI MODE SINGLE MODE
VARIOUS TYPES OF OPTICAL FIBER CABLES • OPGW (Optical Pilot Ground Wire) Cable • ADSS (All-Dielectric Self-Supporting Aerial) type OF Cable • Self-Support AERIAL figure 8 type OF Cable • LASHED type OF Cable • UNDERGROUND / BURRIED type OF Cables • DUCT Type OF Cable
OVERHEAD FIBRE OPTIC CABLE INSTALLATION OPGW WRAP AROUND ADSS
TEST AND MEASUREMENT INSTRUMENTS OTDR SPLICING MACHINE OPTICAL TALK SETS POWER METER, LASER SOURCE, ATTENUATOR MECHANICAL SPLICE TOOL KIT
SOME MANUFACTURERS OF OPTICAL CABLES • Furukawa • Fujikura • LG Cables • Corning • Philips-Fitel • Pirelli • TTL • Sterlite Cables
Questions? Thank You
