ELLIOT, B. (2002). Fiber Optic Cabling (2nd ed.)

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.It isalso a spring-loaded connector which means that the ferrule end-faceseparation is not governed by the adaptor but rather the separation tendsto zero due to the spring action within the mated ferrules.As with all technical advances there are some disadvantages, and thespring-loaded connector is no exception:Springing methodsThere are two methods which can be adopted to produce spring actionwithin the ferrule of a fiber optic connector.The first is sprung body, thesecond sprung ferrule." Sprung body designs (see Figure 6.2).When connected into the appro-priate adaptor and the cable pulled a spring loaded connector canrespond in one of two ways: if the ferrule springing tends to bereleased (i.e.the ferrule ends separate) then the design features asprung body.This simply means that the cable is directly linked to theferrule and the rear body of the connector is spring loaded againstthe ferrule.This type of springing prevents any stress within theconnector but certain users are concerned about interruption of trafficduring the application of pull to the terminated cable and prefer touse sprung ferrule designs.114 Fiber Optic Cabling" Sprung ferrule designs (see Figure 6.3).The alternative to a sprung bodyis a sprung ferrule.In this case there is no movement when the cableis subjected to a pull because the rear body, attached to the adaptor,is directly linked to the cable.The ferrule is therefore spring loadedagainst the body.The disadvantage to this approach is that the terminated fiber within theferrule comes under significant compressive force as the connector istightened or clipped into place within the adaptor.This compressive forcecan, under certain conditions, result in large amounts of optical attenua-tion due to microbending.It is therefore necessary to ensure that thecabling components are relatively free to move and that there are noFigure 6.2 Sprung body connector designFigure 6.3 Sprung ferrule connector designConnectors and joints, alternatives and applications 115constrictions (due to tight fitting of cable to connector, for instance).Thisputs increased responsibility upon the installer in a technical area wellbeyond the expectations of the average contractor.The ST connector is also capable of high performance on single modefiber geometries.The design and manufacturing quality of the adaptors issuch that by the use of tight tolerance ferrules (sized ferrule components)a single mode performance equivalent to the best single mode connec-tors can be achieved.Other connector designsThe SC and ST dominate the world markets; however, there are a numberof other multimode connectors worthy of mention due either to theirhistoric importance or growing influence." SMA.The first mass produced multimode optical connector for thedata communications industry; now obsolete." Biconic.A sprung connector that was favoured by IBM in the early1990s, but offered little in the way of price or performance benefits.Now obsolete." FDDI or MIC connector.A duplex connector in a large body shelldesigned specifically for the FDDI LAN interface.Now obsolete." IBM ESCON�.A duplex connector very similar in appearance to theFDDI MIC connector.Only found on particular IBM mainframes,ESCON Directors and look-alikes from other manufacturers.Onlyapplicable now to IBM mainframe installations." MT.A ribbon or mass termination ferrule developed by NTT specif-ically for optical ribbon cables.It featured one small rectangular ferrulewith 4, 8, 12 or even 16 holes drilled in it.Two alignment pins wereresponsible for the principal alignment and a spring clip held the twoidentical halves together.An index matching gel was usually usedbetween the end-faces to improve performance.The MT becamepopular with PTTs who used high fiber-count ribbon cables." MPO.The MPO uses the MT ferrule inside a larger, spring-loadedplastic housing.It makes the MPO an easy-to-handle connector forregular patching and cross-connect activity.The MT on its own isseen as a demountable splice and too small for patching duties outsideof a patch panel or enclosure." MU.The MU was introduced by NTT in 1995 as a high densitymultiway connector (2, 8 and 16) for transmission systems, opticalswitching and optical backplanes.It is selected for the IEEE P1355FutureBus Architecture." ST.The most commonly used connector for data communica-tions throughout the 1990s.Recognized as an alternative to the SC116 Fiber Optic CablingSC duplex opticalconnectorMT-RJ opticalconnectorFigure 6.4 SC duplex and MT-RJ optical connectorsconnector in structured cabling standards ISO 11801 1st edition,EN 50173 1st edition and TIA/EIA 568A.The ST is no longermentioned in ISO 11801 2nd edition." SC.(Figure 6.4).Originally the Subscriber Connector from Japan.The SC is a push-fit connector in both multimode and single modeversions.It is the first connector of choice in both editions of ISO11801 and EN 50173.It can be supplied in simplex (i.e.one connec-tor) or duplex (i.e.two connectors next to each other) format.Theinternational standards refer mainly to the duplex version." FC.The FC, also from NTT in Japan, has become the industry leadingsingle mode connector.It is more commonly known, however, as theFC-PC, where PC stands for physical contact." Optijack.The first of the new generation SFF or small form factorconnectors.The Fiberjack was introduced by Panduit in 1996.TheFiberjack uses two 2.5 mm ferrules in one single RJ-45 type housing." LC.(Figure 6.5).A duplex SFF connector from Lucent which usedtwo 1.25 mm ferrules.The LC can be split into two simplex connec-tors." VF-45.A ferrule-less duplex connector introduced by 3M, also knowngenerically as the SG or as Volition, when part of 3M s optical cablingsystem, aimed at lowering cost in the fiber-to-the-desk market." MT-RJ.(Figure 6.4).Probably the leading contender in the SFFconnector market and supported by many manufacturers such as AMP(Tyco), Siecor (Corning) and Fujikura.It is based on the original MTferrule design.Connectors and joints, alternatives and applications 117Figure 6.5 LC optical connectorApart from specialist optical connectors for the military and industrialmarkets there are still more optical connectors around for the data andtelecommunications market.There are the D3 and D4 connectors, theE2000, the LX5, the Mini-Mac from Berg handling up to 18 fibers, andthe Mini-MT and SCDC/SCQC both from Siecor (Corning), where DCmeans duplex and QC means quadruplex, or four, fiber terminations.Single mode connectorsSingle mode connectors have to be made to a higher manufacturing toler-ance than multimode connectors, and the use of high-powered commu-nications lasers makes return loss more of an issue within the laser-basedtelecoms market compared to data communications.The connector designs that have been more widely adopted than anyother are the ceramic-based styles originating from the Japanese, normallyunder licence from Nippon Telephone and Telegraph (NTT).TheJapanese dominate the high-quality ceramic industry so it is no surprisethat the connectors using the material as an alignment technique alsocame from that nation [ Pobierz całość w formacie PDF ]

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