FTN design & development specification (D&D)

SP FTN (D&D) 010

Telecommunications Optical Fibre Cables

Issue 1, Feb 2002 · FTN D&D specs & typical drawings

Procurement spec for the FTN's standard 24-fibre singlemode cables (armoured, duct and ZHLS). Designers use it to check cable construction, tube and fibre colour codes, bend radius, attenuation figures, supply lengths and what the product acceptance tests prove.

Clause map — what each clause deals with

1	Introduction	Purpose, scope and definitions for the cable spec.
1.1	Purpose	Procurement spec for PE and ZHLS sheathed fibre trunk cables, built on RT/E/PS/00014.
1.2	Scope	External singlemode G.652 cables; armoured, duct and ZHLS versions, fibre count by order.
1.3	Definitions	Definitions taken from BS 4727-3 Group 13.
2	Optical Fibres	Requirements on the fibre itself before cabling.
2.1	General	Step-index G.652 fibre, continuous with no splices, single source per contract.
2.2	Refractive Index Profile	Core/cladding make-up and the need to state group refractive index at both windows.
2.3	Coating Materials	Coating durability over 30 years, bond strength, strippability force limit, cure, hydrogen evolution, MSDS.
2.4	Proof Test	Proof strain level for 30-year life and the n-value to be stated.
2.5	Fibre Colour Coding	Table of fibre colours per tube (blue, orange, green, brown) and fibre numbering for up to 24 fibres.
2.6	Geometric Requirements	Limits on core/cladding non-circularity, concentricity, cladding and coating diameters.
2.7	Singlemode Waveguide Requirements	Mode field diameter, cut-off wavelength range, chromatic dispersion limits and PMD limits.
2.8	Attenuation Requirements	OTDR trace quality limits (steps, slope changes) and mandrel bend excess loss check.
3	Polyethylene Sheathed Armoured Cable	Construction of the standard armoured cable used in troughing, ducts and direct burial.
3.1	Service Life	Design life in troughing, duct or direct buried.
3.2	Strength Member	Non-metallic continuous central strength member and single-layer tube lay-up.
3.3	Tubes	Tube diameter, tube 1 red and last tube green, gel filling, no water-swellable tapes.
3.4	Fillers	Yellow fillers of tube size with fixed positions.
3.5	Core Binder	Core binder over tubes and fillers.
3.6	Inner Sheath	PE inner sheath material, minimum thickness and thickness ratio.
3.7	Armouring	Longitudinal steel/polymer laminate tape (may be corrugated), tape thickness, oversheath thickness, alternatives.
3.8	Sheath Marking	Legend content, repeat interval and optional sequential length marking.
4	Polyethylene Sheathed Duct Cable	Construction of the lighter single-sheath cable for buried ducts.
4.1	Service Life	Design life in buried duct.
4.2	Strength Member	Polymer-coated metallic central strength member.
4.3	Tubes	Same tube size, colours and filling rules as armoured cable.
4.4	Fillers	Yellow fillers.
4.5	Core Binder	Core binder.
4.6	Moisture Barrier	Longitudinal aluminium/polymer laminate with overlap and thickness requirements.
4.7	Oversheath	PE oversheath material and minimum thickness.
4.8	Sheath Marking	Duct cable legend and optional length marking.
5	ZHLS Sheathed Armoured Cable	Construction of the zero halogen low smoke armoured cable for stations and tunnels.
5.1	Service Life	Design life in troughing or duct.
5.2	Strength Member	Metallic or non-metallic CSM, coated if metallic.
5.3	Tubes	Tube size, colours and filling.
5.4	Fillers	Yellow fillers.
5.5	Core Binder	Core binder.
5.6	Moisture Barrier	Optional aluminium/polymer laminate moisture barrier.
5.7	Inner Sheath	ZHLS inner sheath bonded to the moisture barrier coating, thickness.
5.8	Armouring	Steel/polymer laminate tape with ZHLS oversheath.
5.9	Sheath Marking	ZHLS cable legend and length marking.
6	Product Acceptance Requirements: All Cable Types	The type tests a cable must pass for Product Acceptance.
6.1	Tensile Strength	Tensile test method, load related to cable weight, fibre strain limit.
6.2	Crush Strength	Crush test loads for armoured and duct cable with attenuation monitored.
6.3	Cable Bend	Bend cycling test and the maximum dynamic and static minimum bending radii as multiples of diameter.
6.4	Tube Kinking Test	Tube kink test cycles and statement of tube bend radius.
6.5	Resistance to Water Penetration	Water penetration test (not for ZHLS) with dye check.
6.6	Spark Test on the Oversheath	Spark test voltage and standard.
6.7	Sheath Thickness	How sheath thickness is measured on cut rings.
6.8	Ability to Strip Oversheath of Armoured Cables	Proving armour tape can be removed by hand without damaging the inner sheath.
6.9	Sheath Marking Abrasion Test	Abrasion test force and passes for legend legibility.
6.10	Peel Strength	Peel tests for polymer coating on tapes and sheath-to-tape adhesion.
6.11	Torsion	Torsion test for steel tape armoured cables, seam and sheath checks.
6.12	Impact Test	Impact test energy, impacts and checks for armoured cables.
6.13	Temperature Cycling Test	Full temperature cycling procedure: sample length, looped fibres on OTDR and power meter, cycle temperatures, allowed loss change and component movement limits.
6.14	Optical Attenuation	Attenuation measurement methods and the maximum dB/km in the 1310 and 1550 windows.
6.15	Cable Cut-off Wavelength	Cut-off wavelength test method.
7	Extra Acceptance Requirements for ZHLS Cables	Additional material and fire tests for ZHLS sheathed cable.
7.1	Insulation Resistance	Insulation resistance of ZHLS sheath material after water immersion.
7.2	Water Absorption	Water absorption limit for ZHLS compound.
7.3	Chemical Function Groups	Chemical groups (halogens, phosphorus, sulphur, nitrogen) excluded beyond trace level.
7.4	Smoke Emission	Smoke density test set-up and acceptance against GE/RC8505, flame spread and self-extinguishing.
7.5	Flammability	Bunched cable flame test and char height limit.
8	Production Tests	Routine tests on every production length and the certificates to accompany them.
8.1	All Cable Types	Which section 6 tests are run on all product and which need a stated frequency in the Quality Plan.
8.2	ZHLS Cables	Smoke and flammability tests run during ZHLS production.
8.3	Test Results	What the Certificate of Conformity must list per cable length (drum, type, length, refractive index, attenuation per fibre).
9	Miscellaneous	End sealing, drums, supply lengths and drum labels.
9.1	Sealing and Marking of Ends	Cable ends capped after test.
9.2	Drumming	Drum sizes to Def Stan 81-20, rolling direction arrow, outdoor storage period, battens, non-returnable drums.
9.3	Supply Lengths	Maximum and default supply lengths for duct and ZHLS cables versus armoured.
9.4	Labelling	Information required on the drum label.
10	Approvals	Product Acceptance and OFTEL approval requirements.
10.1	Product Acceptance	Product Acceptance route (RT/LS/P/029), test evidence and notification of design changes.
10.2	OFTEL Approval	Telecommunications Act approval and drum label statement.
11	Safety	Handling, preparation and testing to comply with HSWA 1974.
12	References	Railway and international standards referenced.
12.1	Railway Standards	RT/LS/P/029 and GE/RC8505.
12.2	International Standards	BS, BS EN, IEC, ITU-T and legislation referenced.