Tertiary copper & fiber cabling

Tertiary VDI cabling complies with 3 structuring standards: the reference standard for generic copper and fiber networks in tertiary environments, ISO/IEC 11801 (application classes) and NF C 15-100 for the associated high-voltage currents. Category 6a is becoming the minimum standard on new floors: it supports 10 GbE up to 100 meters, compared with 55 meters for classic category 6 (classes EA and E). The widespread shift to cloud very significantly increases internal bandwidth consumption over five years, which makes class EA (Cat 6a) unavoidable.

On the optical fiber side, two media coexist in tertiary offices:

• OM4 multimode: 40 Gb/s over 150 meters, floor-to-floor distribution from a main server room on an intermediate level (3rd to 5th floor).
• OS2 single-mode: 100 Gb/s beyond one kilometer, essential for multi-building sites or campus links.

Our reading diverges from the dominant installer discourse on all-Cat 6a. On a standard tertiary floor operated at 1 Gb/s per workstation, Cat 6a brings no immediate throughput benefit: its value lies exclusively in PoE++ (IEEE 802.3bt, 90 W), which powers LED lighting, screens and Wi-Fi 6E access points, i.e. a significant share of the sockets on a modern floor. The justification is energy-related and functional, not network-related. On the tertiary sites we audit, a majority retain Cat 5e or Cat 6 cabling more than 12 years old, incompatible with these new uses.

Kytom’s 5-step method aligned with the 12-week project timeline

The Kytom process is structured around 5 milestones synchronized with the standard 12-week timeline.

1. Audit of the existing setup (weeks 1-2): inventory of the 180 to 220 typical sockets of an 850 m² floor, testing of in-place links, mapping of racks and cable trays.
2. Design (weeks 3-4): sizing at 2 RJ45 sockets per workstation, plus 1 socket per 10 m² in shared areas, and 4 to 8 fiber strands per floor.
3. Procurement (week 5): selection of manufacturers with 25-year warranties and validation of technical references based on the normative framework applicable to tertiary cabling.
4. Deployment (weeks 6-10): U/FTP category 6a pulling under trunking or false ceilings, patching in 42U racks, standardized labeling.
5. Acceptance and certification (weeks 11-12): Fluke DSX-8000 tests on all copper links, OTDR on fiber, delivery of the as-built documentation.

The teams mobilized are B1V/H1V qualified and manufacturer-certified. The scope of works remains compliant, with a single technical referent throughout the project duration.

For the CIO: availability, TCO control and traceable audit

VDI cabling is not a layout matter, it is an SLA and network OPEX matter over 15 years. Well-sized Cat 6a + OS2 fiber cabling supports high network availability, helps control TCO over 15 years and extends the service life of the infrastructure. For a CIO, improving availability dramatically reduces annual network downtime, turning hundreds of hours of potential outage into just a few hours.

Fluke DSX-8000 certification across all links provides an auditable file enforceable against the manufacturer over 25 years: each port has its report, each report has its ID.

Copper-fiber-PoE pooling removes a significant portion of specialized cabling (telephony, alarm, access control), which explains the drop in total cost of ownership. PoE avoids a significant share of dedicated power supplies, in direct alignment with the objectives of the tertiary decree published on the ADEME platform.

When the VDI overhaul is not justified. On a floor of less than 300 m² retaining Cat 6 cabling less than 8 years old and operated at less than 1 Gb/s per workstation, a Cat 6a + OS2 overhaul rarely offers a satisfactory return on investment: it is generally more appropriate to keep the existing setup, occasionally add fiber links and postpone the overhaul. Likewise, on sites with short leases (less than 4 years remaining) without landlord agreement, full Cat 6a pre-cabling cannot be amortized on the tenant side; targeted Cat 6 cabling is sufficient.

Points of attention: EMC 30 cm, TSB-184-A thermal derating, occupied sites

3 constraints deserve particular attention during the execution phase.

• High-voltage/low-voltage coexistence: NF C 15-100 requires a minimum 30 cm parallel separation, failing which electromagnetic interference may occur on the links concerned.
• Cable tray saturation: existing trunking is frequently close to its maximum capacity on the tertiary sites audited, requiring replacement or doubling and potentially extending the schedule by several weeks.
• PoE++ heating: a bundle of 24 Cat 6a cables under 90 W can reach 60 °C in a closed conduit, requiring thermal derating compliant with TSB-184-A (TIA TSB-184-A, 2017).

The subscribed power of a 500 to 1,000 m² floor accommodating 70 to 100 workstations is generally between 50 and 100 kVA, with reserve to be provided for event uses and the upcoming IoT deployment.

On occupied sites, noisy phases (slab drilling, ceiling removal) are scheduled outside the 9am-6pm window, which extends the project duration but preserves business continuity.

Application limits: these constraints apply to a standard tertiary office. In industrial environments (reinforced EMC, IP54+), data centers (density above 500 W/m²) or U/J-type public-access buildings (hospitals, nursing homes), the thresholds and methods differ and require specific studies.