A Tutorial on Centralized Optical Fiber Cabling Networks Part III

A Tutorial on Centralized Optical Fiber Cabling Networks Part III


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A Tutorial on Centralized Optical Fiber Cabling NetworksPart IIIby Douglas E. Harshbarger and George Sellardhe centralized optical fiber and their multiple termination and cable trays. Now we don’t runnetwork design provides points, installation crews must carry the innerduct. This cuts down onT direct connections between equipment and cable reels to several time and expense.”hundreds, even thousands, of work- locations. With a centralized design, For those responsible for con-stations and a single main cross- cable reels are set up at one point, necting, activating and managingconnect (MC) by using the main cross-connect. Termina- the network, centralized designFIBERpull-through optical fiber cables, or tions are performed at one location. brings many benefits, according toOPTICSa splice or interconnect in the Darryl Wolford,president of Com- Charles B. Orr, of Sellard Communi-telecommunications closet (TC). munication Design Specialists cations.With all network electronics con- (CDS), of Weedsport, N.Y., has over- “It’s much easier to make thesolidated in the main cross-con- seen numerous centralized installa- cross-connects and keep track ofnect, the centralized design will tions, and he sees many benefits to them,” Orr said. “It allows you toreduce the number of telecommu- the design. “Everything coming activate everything from one pointnications closets, eliminate the back to one point cuts down on rather than tracing lines to telecom-need for ...



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A Tutorial on Centralized by Douglas E. HarshbargerPand GeorgeaSellardrt III Optical Fiber Cabling Networks he centralized optical fiberand their multiple terminationand cable trays.Now we don’t run network design providespoints, installation crews must carrythe innerduct.This cuts down on huTlocations. With a centralized design,ndreds, even thousands, of work-For those responsible for con-direct connections betweenequipment and cable reels to severaltime and expense.” stations and a single main cross-cable reels are set up at one point,necting, activating and managing connect (MC) by using themain cross-connect.Termina- thenetwork, centralized design FIBER pull-through optical fiber cables, ortions are performed at one location.brings many benefits, according to OPTICS a splice or interconnect in theDarryl Wolford, president of Com-Charles B. Orr, of Sellard Communi-telecommunications closet (TC).munication Design Specialistscations. With all network electronics con-(CDS), of Weedsport, N.Y., has over-“It’s much easier to make the solidated in the main cross-con-seen numerous centralized installa-cross-connects and keep track of nect, the centralized design willtions, and he sees many benefits tothem,” Orrsaid. “Itallows you to reduce the number of telecommu-the design.“Everything comingactivate everything from one point nications closets, eliminate theback to one point cuts down onrather than tracing lines to telecom-need for costly HVAC (heating ven-labor,” hesaid. “Having multiple ter-munications closets and desktops.” tilation and air-conditioning) equip-mination points is difficult becauseOrr currently is helping to com-ment in the eliminated closets andyou have so many points to go to.I pletework installing a centralized more efficiently use multiuser elec-find it difficult to direct people tooptical fiber network on a high tronics. Thefiber-to-the-desk infra-different places.With the central-school BOCES (Board of Coopera-structure also future proofs theized network, you don’t have totive Educational Services) campus. network against tomorrow’s band-direct your crew so much.This “Disruptionis a big thing during width requirements.minimizes time and cuts down onany installation,”Orr said. However, The centralized optical fiberlabor costs.the centralized design allows Orr to design provides a stable building“Everything comes back to onedo virtually all his work from a sin-cabling infrastructure.This is cru-hub room,”Wolford continued. “Wegle location, the main cross-con-cial in an era when informationmight have a few splices, but that’snect. “Inever have to go in a technology is continually improv-all.” InWolford’s experience, splicesclassroom, where the computers ing, placing ever greater demandsare more common than intercon-are,” hesaid. “I don’t have to disturb on the information-carrying capaci-nects at the telecommunicationsstudents to activate a port.” ty of networks.The centralizedclosets. “Splices eliminate points ofFor Orr, the centralized network design also facilitates the constantfailure,” hesaid. “Oncethese aredesign “isa dream, because the MC moves, adds and changes so com-done, we never go back to them.”houses are all active electronics.” mon in today’s businesses. More-Wolford emphasized that even Standards over, a centralized design greatlywithout a centralized design, intra-eases installation.building fiber installations areInstalling a centralized fiber net-becoming increasingly easier andwork is made easier by the fact that Installation SimplifiedInstandards are well developed.practically routine. “We don’t treat For the installer, the centralizedthe fiber as anything specialSeptember 1995, the TR-41.8.1 cabling design simplifies logisticsbecause it doesn’t require specialcommittee of TIA approved publi-and reduces installation time andtreatment,”Wolford said. “For exam-cation of Telecommunications Sys-labor. Withdecentralized networksple, we used to put in innerducttems Bulletin (TSB) 72, Centralized
Optical Fiber Cabling Guidelines to sup-Figure 1Centralized Cabling from TS B72 Horizontal Cable plement the Commercial Building Telecommunications Cabling Standard Interconnect Term. Pos. ANSI/TIA/EIA 568A regarding the design or Splice and installation of centralized opticalPathway Telecommunications WorkArea fiber cabling.(See Figure 1.)Backbone Cable Closets The TSB72 purpose and scope consists of “implementationguidelines and con-Pull-through Term. Pos. Cable necting hardware requirements when implementing centralized optical fiber Backbone PathwayWork Area cabling systems.” TSB72 specifies the use lized of pull-through cables, interconnects orTerm. Pos.Centra Cross-connect splices in the telecommunications closet. It also notes that interconnection offers Equipment Room increased flexibility. Term. Closely following these guidelines Hardware ensures the flexibility and easy manage-Equipment ment of optical fiber links as well as the ability to migrate to an active horizontalpull-through, interconnect or splicelowers overall expenses.Furthermore, cross-connect (HC) at the telecommuni-implementation to cross-connect imple-due to the design’s simplicity and to the cations closet if this is required.For mentation.It also offers specifications foravailability of standards, installation is sim-example, TSB72, followingANSI/TIA/EIA theaddition and removal of cables, label-plified and initial costs are reduced.For 568A, limits the combined length of theing and other key installation parameters.these and many other reasons, the optical backbone and horizontal cabling betweenTSB72 also lists connecting hardwarefiber centralized design is quickly becom-the centralized cross-connect and therequirements for joining the fibers froming a popular alternative for network telecommunications outlet to 300 m.the backbone and horizontal cables.It designers.CBM Strict adherence to this specification willrecommends that either re-mateable con-Harshbarger is marketDouglas E. assure the performance of the installednectors or splices be used, but not both atdevelopment engineering manager, multimode optical fiber at multi-gigabita single facility.premises systems, for Corning Inc. speeds. Thecentralized optical fiber cablingGeorge Sellard is president of Sellard In addition,TSB72 covers the maximumdesign provides a cost-effective alterna-thanks toCommunications. Special length of pull-through cables and pro-tive to the traditional, distributed designPatrick Scanlon of Rochester Institute of vides guidelines for the migration frombecause using fewer active componentsTechnology for his assistance.