¶ STN-DRAFT - Structured Cabling Standard
Summary: Defines the minimum requirements for copper Ethernet cabling and the selection criteria for single-mode and multimode fibre in new and upgraded installations.
| Field |
Value |
| Author |
Mike |
| Owner |
Infrastructure |
| Status |
Draft |
| Version |
0.1 |
| Last Reviewed |
2026-05-05 |
| Review Due |
2026-08-05 |
| Approver |
— |
| Approved Date |
— |
| Version |
Date |
Author |
Description |
| 0.1 |
2026-05-05 |
Mike |
Initial draft |
⚠️ Draft
This standard is a draft and has not been reviewed or approved. Do not apply it until it has been signed off.
This standard defines the minimum specification for structured cabling in new installations and upgrades. It covers copper Ethernet horizontal cabling, and the selection criteria and use cases for single-mode fibre (SMF) and multimode fibre (MMF). Its purpose is to ensure all cabling infrastructure is consistent, documented, tested, and capable of supporting current and near-future bandwidth requirements without re-cabling.
This standard applies to all new cabling installations and any upgrade or replacement of existing cabling across all sites. It covers:
- Horizontal copper cabling from patch panels to outlet plates
- Patch cables used in MDFs, IDFs, and at the desktop
- Fibre backbone runs between MDFs and IDFs, between buildings, and within data centre environments
Out of scope: wireless infrastructure, coaxial cabling, and existing cabling not subject to fault repair or upgrade. Existing compliant installations are not required to be upgraded solely to meet this standard.
- All new horizontal copper runs shall use Cat6A (10GBASE-T rated) as the minimum specification. Cat6 and Cat5e are not permitted for new horizontal runs.
- The maximum permanent link length (patch panel to outlet plate, excluding patch cables) shall not exceed 90 metres. The maximum channel length (end-to-end including all patch cables) shall not exceed 100 metres.
- All copper runs shall be terminated to the T568B wiring standard at both ends.
- Patch cables shall be Cat6A stranded-conductor with snag-proof boots. Solid-core cable shall not be used as patch cable.
- Copper data cables running parallel to AC power cables shall maintain a minimum physical separation of 150 mm. Where cables must cross, they shall do so at 90 degrees.
- Every installed run shall be tested end-to-end with a certified cable tester capable of Cat6A validation (e.g. Fluke DSX series). Test results shall be retained for the life of the installation.
- All cable runs shall be labelled at both ends with a unique identifier. Labels shall correspond to the patch panel port documentation.
- SMF shall be OS2 specification, compliant with ITU-T G.657.A2 (low-bend-loss). Standard G.652.D is acceptable for long straight runs where bend radius is not a concern.
- SMF shall be the required medium for:
- All inter-building runs regardless of distance
- Any intra-building run exceeding 300 metres
- All campus backbone and dark fibre connections
- All carrier or WAN hand-off connections
- LC duplex connectors shall be used for all equipment connections. MPO/MTP connectors shall be used for high-density pre-terminated trunk systems.
- APC (Angled Physical Contact, 8° polish) patch leads shall be used on SMF links where the connected equipment supports APC connectors. UPC connectors are acceptable where APC is not supported, but shall not be mixed with APC on the same link.
- Every SMF run shall be documented with a bi-directional OTDR trace at both 1310 nm and 1550 nm. Traces shall be retained for the life of the installation.
- End-to-end insertion loss on SMF links shall not exceed 3.0 dB, including connectors and splices.
- MMF shall be OM4 (50/125 µm, laser-optimised) as the minimum specification for all new installations. OM3 is not permitted for new work. OM5 shall be used where SWDM (Short Wavelength Division Multiplexing) or wavelength reuse is a current or planned requirement.
- MMF shall be used for intra-building backbone runs where the distance is within the following limits:
| Speed |
OM4 Max Distance |
OM5 Max Distance |
| 10 Gbps |
400 m |
400 m |
| 40 Gbps |
150 m |
150 m |
| 100 Gbps |
100 m |
150 m |
- MMF shall not be used for inter-building or campus backbone runs — SMF is required for all such links (see requirement 9).
- LC duplex connectors shall be used for all MMF equipment connections. MPO/MTP connectors shall be used for high-density trunk systems.
- End-to-end insertion loss on MMF links shall not exceed 3.5 dB, including connectors and splices.
- Every MMF run shall be tested with an optical power meter and light source. An OTDR trace is recommended but not mandatory for runs under 100 metres.
- All fibre connectors shall use UPC polish as a minimum. APC is required on SMF per requirement 11.
- All fibre runs shall be labelled at both ends with a unique identifier. Labels shall indicate fibre type (OS2, OM4, or OM5), the connector polish (APC or UPC), and the number of cores.
- Bend radius shall not be violated during installation. Minimum recommended bend radius is 30 mm for OS2 low-bend fibre and 50 mm for OM4/OM5.
Cat6A is specified in preference to Cat6 because Cat6 achieves 10GBASE-T only up to 55 metres, making it unsuitable for full-length horizontal runs without performance risk. Cat6A provides 10GBASE-T to the full 100-metre channel and is now cost-competitive with Cat6 in volume.
T568B is the prevailing commercial wiring standard in the UK and Europe and ensures consistency across patch panels and outlets from different vendors and installers.
OS2 fibre is specified for all SMF work because its low-bend-loss characteristic (G.657.A2) accommodates tight routing in conduit and trunking without signal degradation, and it supports wavelengths from 1260 nm to 1625 nm — making it compatible with any current or future transceiver technology including CWDM and DWDM, without requiring re-cabling.
OM4 is specified as the minimum MMF grade because OM3 limits 40G to 100 metres and 100G to 70 metres — insufficient for many IDF-to-MDF runs. OM4 extends these distances to 150 m and 100 m respectively and is widely available at comparable cost. OM5 is called out specifically for SWDM use cases, which use four wavelengths in the 850–950 nm range to multiply capacity over a single OM5 fibre pair.
The separation of SMF and MMF into distinct use cases (inter-building vs. intra-building) reflects both the cost of SMF transceivers and the fact that short-reach VCSEL-based transceivers used with MMF are significantly cheaper than SMF equivalents. This standard preserves the cost benefit of MMF for short in-building runs while mandating SMF where longevity and distance demand it.
Exceptions to this standard require written approval from the Infrastructure Owner before work begins. The following scenarios are pre-approved without individual sign-off:
- Existing Cat6 or Cat5e horizontal runs may remain in service where they demonstrably meet the performance requirements of the connected equipment. Replacement is required on fault or when the connected equipment is upgraded to 10GBASE-T.
- Existing OM3 fibre may remain in service in locations where it meets the current link speed and distance requirements. Replacement is required on fault or when link speed requirements exceed OM3 capability.
- Where a third-party contractor or building landlord provides cabling infrastructure that does not meet this standard, the deviation shall be documented and the Infrastructure Owner notified. Remediation shall be scoped at the next available opportunity.