OPTICAL FIBER COMMUNICATION

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Transcript of OPTICAL FIBER COMMUNICATION

OPTICAL FIBER COMMUNICATION

OPTICAL FIBER COMMUNICATIONSubmitted By:Umang BhatiaRoll No: 12450

OUTLINESummer Training at Signal and Telecommunication Department North Eastern Railways, Izatnagar, Bareilly from 15th June, 2015 to 11th July, 2015.An amazing experience as I got to see, how exactly the communication system works for Indian Railways.Main Objective was to learn Optical Fiber Communication In Railways.

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OPTIC FIBER An optical fiber is a cylindrical dielectric waveguide made of low-loss materials such as silica glass. It has two main component layers: A Core & A Cladding.It has a central core in which the light is guided, embedded in an outer cladding of slightly lower refractive index.It works on the principle of total internal reflection

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INSIDE OPTICAL FIBER CABLE4

Core thin glass center of the fiber where light travels.Cladding outer optical material surrounding the coreBuffer Coating plastic coating that protects the fiber.

TYPES OF OPTICAL FIBER5

TYPES OF OPTICAL FIBER(conti) SINGLE MODE FIBERUsed to transmit one signal per fiber.Used in telephone and cable TV.They have small cores(9 microns in diameter) .Transmit infra-red light from laser.

MULTI MODE STEP INDEX FIBER Used to transmit many signals per fiber.Used in computer networks. They have larger cores(62.5/50 microns in diameter) Transmit infra-red light from LED.6 MULTI MODE GRADED INDEX FIBER Core diameter : 50/62.5 microns.Cladding size: 125-140 microns.Refractive index changes continuously.Low dispersion.Core refractive index is made to vary as a function of the radial distance from the center of the fiberOM1: refer to the commonly used 62.5/125 multimode fiber.OM2: refer to the commonly used 50/125 cable.Both OM1 and OM2 easily supports applications ranging from Ethernet to gigabit Ethernet.OM3: Typically this fiber optic patch cable is with 50/125 multimode fiber, with aqua jacket.They support bandwidth up to 10GB upto 300 meters.

PROPAGATION IN OPTICAL FIBER7

COLOR COATING8

Fiber geometry parametersThe three fiber geometry parameters that have the greatest impact on splicing performance include the following:Cladding diameterCore/clad concentricity (or core-to- cladding offset)Fiber curl9

LOSS MECHANISMS10

24 fiber cable used in Indian Railways11

COMPARATIVE STATEMENTADVANTAGESWide bandwidthLight weight and small sizeImmunity to electromagnetic interferenceLack of EMI cross talk between channelsLack of sparkingCompatibility with solid state sourcesNo emission licensesDISADVANTAGESHigh investment costNeed for more expensive transmitters and receiversFragility OpaquenessRequires special skills12

AREAS WHERE WE CAN USE ITMedicalUsed as light guides, imaging tools and also as lasers for surgeries Defence/GovernmentUsed as hydrophones for seismic and SONAR uses, as wiring in aircraft, submarines and other vehicles and also for field networking Data StorageUsed for data transmission TelecommunicationsFiber is laid and used for transmitting and receiving purposes NetworkingUsed to connect users and servers in a variety of network settings and help increase the speed and accuracy of data transmission Industrial/CommercialUsed for imaging in hard to reach areas, as wiring where EMI is an issue, as sensory devices to make temperature, pressure and other measurements, and as wiring in automobiles and in industrial settings 13

JOINING OF FIBER- SPLICING14

Mechanical splicingFusion splicingReflection losses(-45 db to -55 db)No reflection lossesInsertion loss(0.2 db)Very low insertion loss(0.1 db to .15 db)cost highComparatively less

Possible Alignment Error During Splicing15

OPTICAL COMMUNICATION SYSTEM16

PULSE CODE MODULATION17

TIME DIVISION MULTIPLEXINGTime on the information channel, or fiber, is shared among the many data sourcesThe multiplexer MUX can be described as a type of rotary switch, which rotates at a very high speed, individually connecting each input to the communication channel for a fixed period of timeThe process is reversed on the output with a device known as a demultiplexer, or DEMUX18

WAVELENGTH DIVISION MULTIPLEXINGData from each TDM channel is loaded on one optical frequency (or wavelength, ) of a particular wavelength bandThese wavelengths are then multiplexed onto one fiber with the help of WDM multiplexersOther side of the network these wavelengths are demultiplexed by using either optical filters, gratings or WDM demultiplexer

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PLESIOCHRONOUS DIGITAL HIERARCHY (PDH)In Europe a standard was adopted where thirty-two, 64kbit/s channels were combined to produce a structure with a bit rate of 2.048 Mbit/s (usually referred to as 2 Mbit/s) Four, 2 Mbit/s signals were combined together to form an 8 Mbit/s signal (actually 8.448 Mbit/s).As the need arose further levels of multiplexing structure were added to include rates of 34 Mbit/s (34.368), 140 Mbit/s (139.264) and 565 Mbit/s (564.992). These transmission speeds are called Plesiochronous Digital Hierarchy or PDH ratesAlthough each of the systems works fine as a stand-alone hierarchy, it does make international inter-connection very difficult and costly This was the major reason for the development of a new internationally agreed standard

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PDH (conti..)21

DEMISE OF PDHBit interleaving multiplexing Lack of Flexibility Lack of consensus on standardsLimited Network Management/debugging Defined for selected topologiesMode of TransmissionLess bandwidth compared to SDH

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SYNCHRONOUS DIGITAL HIERARCHY (SDH)SYNCHRONOUS :ONE MASTER CLOCK & ALL ELEMENTS SYNCHRONISE WITH IT.DIGITAL: INFORMATION IN BINARY.HIERARCHY: SET OF BIT RATES IN A HIERARCHIAL ORDERAt each hierarchical level, synchronous transport module is formed with information pay-load and overhead bits and a synchronizing mechanism is in-built to ensure all network elements work to a master clock referenceAll the limitations of PDH are removed in SDH High transmission ratesSimplified add & drop functionHigh availability and capacity matchingReliabilityFuture-proof platform for new servicesInterconnection

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Building Block of SDH24

SDH Transport Rates25

Signal LevelSTM-1STM-4STM-16STM-64

Rate (Mbps)155.52622.082488.329953.28

CapacityVoices63 E13 E31 E4252 E112 E3 4 E41008 E148 E316 E44032 E1192 E364 E418901440192075605760768030240230403072012096092160122880

ADVANTAGES OF SDH SDH permits the mixing of the existing European and North American PDH bit ratesAll SDH equipment is based on the use of a single master reference clock source & hence SDH is synchronousCompatible with the majority of existing PDH bit ratesSDH provides for extraction/insertion, of a lower order bit rate from a higher order aggregate stream, without the need to de-multiplex in stages.SDH provides for a standard optical interface thus allowing the inter-working of different manufacturers equipment26

Any Questions or Comments?27

28THANK YOU