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FTN design & development specification (D&D)

SP FTN (D&D) 008

Network Design Manual for Optical Fibre

Issue 4.2, Feb 2009 · FTN D&D specs & typical drawings

The core fibre design manual for the FTN: how Core and Access Nodes connect, where joints and spurs go, which fibres and tubes are allocated to what, resilience rules and how to work out the loss budget. Essential for anyone producing a detailed fibre design.

Clause map — what each clause deals with

1IntroductionWhy the manual exists: consistent fibre design principles for designers producing the detailed FTN fibre design.
2AbbreviationsAcronym list (ADM, BTS, DBS, DI-SAC, HLD, PMux, REB, STM-1, STM-16, UTX etc.).
3GlossaryDefinitions of key terms: Access Node SR/DR, Core Node, fibre section and sub-section, spliceless joint, green zone, touch potential, Network End/User End.
4ScopeWho must follow the manual, mandatory status, and the Technical Clarification and Design Concession routes for departures.
5SafetyDesigner's duty not to introduce new hazards when applying the manual.
6Connectivity & InterfacesInterfaces with other rail projects and PTOs needed to close transmission rings; info supplied by Network Rail.
7FTN ArchitectureOverview of the SDH ring-based FTN and its node types.
7.1General PrinciplesRing topology, the 17 node types grouped into Core and Access, and dedicating tubes in a 24-fibre cable to core or access traffic.
7.2Core NodesRole of Core Nodes as the key interfacing points between transmission rings.
7.3Access NodesWhat Access Nodes do and the split into SR (single route, one ADM) and DR (diverse routes, multiple ADMs), with the node Types each covers.
7.4GSM-R RepeatersHow tunnel and in-fill repeaters link to a hub over fibre: single-fibre working, back-up fibre, pulled bundled fibre, FC/APC pigtails, green patchcords, dedicated cables.
8Surveying RequirementsWhat the fibre survey must capture in addition to SP/FTN(SU)/001: lengths, joint positions, crossing joints, sheath gaps, spurs, terminations, route separation, building entries.
8.1Centre to centre cable lengthsHow cable lengths between joints are measured and the allowances added for deviation, jointing and termination; rule that cables terminate at nodes not joints.
8.2Joint LocationsNominal joint spacing and concession limit, green zone siting, joint bays, tunnel mouth joints, spliceless joints near stations and level crossings for CCTV, DI-SAC differences.
8.3Sheath GapsWhy metallic sheaths are gapped to control traction voltages; points to SP/FTN(D&D)/005 for the detail.
8.4Core Node SitesCore Nodes need physically diverse cables into buildings or REBs, meeting the resilience rules in section 14.
8.5Access Node SitesSpur cable arrangements for SR and DR Access Nodes, the Stakka box and temporary closure arrangement where the node is not yet built, survey allowances.
8.6Choice of Cable TypeThe four cable types (duct, armoured, ZHLS, DI-SAC), what each is for, and the environment-to-cable-type selection table including subsurface stations and building entries.
9Fibre Cabling ArrangementsHow fibre cables are arranged at joints, terminations and node sites.
9.1GeneralUse the same Network Rail nominated components everywhere; arrangements vary with node type and resilience.
9.2Optical Joint ClosuresThe free-issued joint closure kit (FIST GCO2 with SOSA2 trays) and where closures are housed.
9.3Optical TerminationsThe free-issued termination kit (Splice UK, to 011), its pigtails to 012, and the housings terminations go in.
9.4Core NodesCore Node purpose, separate building entries per cable, dedicated tube per Core-to-Core link with spare pair retained, minimum splices.
9.5Access NodesAccess Node functions, daisy-chaining between Core Nodes, when a second fibre pair or tube is needed (Figures 1 to 3), spur splicing and spliceless joints.
9.6Connection of Transmission Nodes After Cable CommissioningConnecting a node whose position moved after cable installation: extended spur up to a limit, or inserting a new cable length with two joints.
10Optical Fibre Splicing ArrangementsNetwork Rail's splicing requirements at joints and terminations, read with Appendix C drawings.
10.1GeneralScope of the splicing section and link to Appendix C.
10.2Through JointsLike-to-like splicing by colour and tube at straight joints; DI-SAC to standard cable follows the Appendix D schedule.
10.3Spur JointsDefinition of a spur joint, how many tubes are spliced for each Access Node type, and the tube 3 arrangement for tunnel repeater spurs.
10.4Terminations at Core NodesAll fibres spliced to tuned SC/APC pigtails at Core Nodes; drawing reference.
10.5Terminations at Access NodesOnly selected fibres terminated at Access Nodes, use of ODF Connectivity Drawings to place fibres on the right trays, and back-splicing in temporary closures.
11AccommodationWhere fibre cables, joints and terminations are housed.
11.1Optical Fibre CableCables (other than DI-SAC) go in the lineside route built or refurbished to 004 and 007.
11.2Optical Fibre JointsJoints in re-enterable dome closures in perpendicular joint bays per SU/001 and 004.
11.3Optical Fibre terminationsTermination kits, pigtails and the housings (trackside cabinets, REBs, buildings) used for terminations.
12Detailed Optical Fibre DesignsWhat a detailed fibre design must contain: all terminations, splices and cables on a line diagram with numbers, distances and losses; sample in App B.
12.1Controlling Undesirable Effects of Electrification CurrentsTouch potential control for fibre cables: keep metallic elements earth-free by gapping armour and isolating moisture barriers and strength members, per 005.
13Allocation of FibresThe standard fibre and tube allocation table for 24-fibre cables (access traffic, second ADM, repeaters, CCTV, core rings and spares); no departures without concession.
13.1Allocation of Fibres for GSM-R Tunnel and In-fill RepeatersWhich fibres and tubes feed each numbered repeater in main cable and DI-SAC, and allocations for a dedicated repeater cable.
14ResilienceRules to avoid common mode failures: separate building entries per cable, PTO entries, minimum separation between entries and between FTN cables, ducted alternative with concession.
15Loss BudgetHow to calculate and check optical loss on sections and sub-sections.
15.1GeneralWhat the loss budget is, factors affecting loss, and the maximum link loss at 1550 nm beyond which clarification is needed.
15.2Optical cable attenuationCable/fibre supplier, and the per-km attenuation figure to use in calculations.
15.3Splice LossDefinition of splice loss as a bidirectional mean; allowances and testing are in 005.
15.4Connector LossDefinition of connector loss and the design figure to use.
15.5Calculation of expected section lossFormula table for Core-to-Core section loss: fibre km, splices and connector pairs.
15.6Calculation of expected sub-section lossFormula table for Access Node sub-section loss.
15.7Calculation of expected section loss with temporary back splicesHow back-spliced spur cables add loss (double spur length, extra splices, Access Node connectors) and the formula table.
16Labelling, Numbering and As-Built RecordsLabel fibre elements to the FTN Numbering Plan (016) and compile as-builts to 017.
17StandardsList of referenced FTN specs and standards.
App ATypical Fibre Cabling ArrangementsDrawing list for typical cabling at Access Node, Core Node, MSC and Type 15 sites, including junctions and node-not-ready cases.
App BFibre Section Sample DrawingReference to the sample detailed design drawing DR/FTN(D&D)/013.
App CFibre Splicing DiagramsDrawing list for spur, back splice, termination, DI-SAC and GSM-R repeater splicing arrangements, plus generic ODF connectivity drawings.
App DDouble Insulated Super Armoured Cable (DI-SAC)DI-SAC construction, bend radius, joint spacing rules, sheath gap need, installation summary, two-tube fibre colour code, tube labelling and the cross-splicing schedule to standard cable.
App EGeneric ODF Connectivity DrawingsGeneric ODF connectivity drawings for Type 16 nodes (drawings only, no text).

Standards this one points to