NAME : S.PRIYADHARSINIYEAR : III YEARSECTION : ECE –AREG NO : 1090110103283GAGET : OTDRDATE : 07-10-2011
OTDROptical Time-Domain Reflectometer Image from exfo.com
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 toanother without much attenuation or loss.The glass used to make Optical Fibers is so pure that if thePacific Ocean was filled with this glass then we would be ableto see the ocean bottom form the surface….!!!!This is to be believed as repeater distances on long haul routesfor optical fibers vary from 50 to 150 km.
Working of Optical fibers?The light source (LAZER) atthe transmitting (Tx) end ismodulated by the electricalsignal and this modulated lightenergy is fed into the OpticalFiber.At the receiving end (Rx) thislight energy is made incidenton photo-sensors whichconvert this light signal back toelectrical signal.
Why Optical Fibers ?As mans need and hunger for communication increased, the amount ofbandwidth required increased exponentially.Initially we used smoke signals, then horse riders for communicating. Butthese ways were way to slow and had very little bandwidth or data caringcapacity.Then came the telephone and telegraph that used copper wires forcommunication. But soon demand out striped the capacity and capability ofcopper wires and data transport got added to voice communication. Thencame Coaxial copper cables, VHF and UHF Radios, Satellite but demand stilloutstripped 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.
OTDR Uses Measure loss Locate breaks, splices, and connectors Produces graphic display of fiber status Can be stored for documentation and later reference Cable can be measured from one end
VARIOUS TYPES OF OPTICAL FIBER CABLES 1. OPGW Cable 2. ADSS type OF Cable 3. Self-Support AERIAL figure 8 type OF Cable 4. LASHED type OF Cable 5. UNDERGROUND / BURRIED type OF Cables 6. DUCT Type OF Cable
ADVANTAGES OF OPTICAL FIBERS1. VERY HIGH INFORMATION CARRING CAPACITY.2. LESS ATTENUATION (order of 0.2 db/km)3. SMALL IN DIAMETER AND SIZE & LIGHT WEIGHT4. LOW COST AS COMPARED TO COPPER (as glass is made from sand..the raw material used to make OF is free….)5. GREATER SAFETY AND IMMUNE TO EMI & RFI, MOISTURE & COROSSION6. FLEXIBLE AND EASY TO INSTALL IN TIGHT CONDUICTS7. ZERO RESALE VALUE (so theft is less)8. IS DILECTRIC IN NATURE SO CAN BE LAID IN ELECTICALLY SENSITIVE SURROUNDINGS9. DIFFICULT TO TAP FIBERS, SO SECURE10. NO CROSS TALK AND DISTURBANCES
DISADVANTAGES OF OPTICAL FIBERS…1. The terminating equipment is still costly as compared to copper equipment.2. Of is delicate so has to be handled carefully.3. Last mile is still not totally fiberised due to costly subscriber premises equipment.4. Communication is not totally in optical domain, so repeated electric – optical – electrical conversion is needed.5. Optical amplifiers, splitters, MUX-DEMUX are still in development stages.6. Tapping is not possible. Specialized equipment is needed to tap a fiber.7. Optical fiber splicing is a specialized technique and needs expertly trained manpower.8. The splicing and testing equipments are very expensive as compared to copper equipments.
APPLICATIONS OF OPTICAL FIBERS…1. LONG DISTANCE COMMUNICATION BACKBONES2. INTER-EXCHANGE JUNCTIONS3. VIDEO TRANSMISSION4. BROADBAND SERVICES5. COMPUTER DATA COMMUNICATION (LAN, WAN etc..)6. HIGHT EMI AREAS7. MILITARY APPLICATION8. NON-COMMUNICATION APPLICATIONS (sensors etc…)