How we think about sustainability.
Dark fibre is, by category, one of the lower-carbon connectivity choices a UK business can make. Passive infrastructure in the ground. Long asset life. Lower power draw than active leased-line equipment that gets refreshed every few years. The fibre we put in for Ask4 in 2024 will still be the same fibre under the network in 2044.
We’ve published a longer version of this argument. The summary’s on this page.
Four structural reasons.
Passive in the ground
Once dark fibre is installed, the cable itself draws no power. The electronics light it at each end. So the route between sites — often the longest part of the network — has no active kit pulling current 24/7. Leased-line services route through powered carrier equipment along the way; dark fibre doesn’t.
Long asset life
Telecoms fibre has a working life measured in decades. Properly installed, it outlasts the equipment lighting it by a generation. The active equipment refreshes on a 5–8 year cycle. The fibre underneath stays put.
Bandwidth upgrade without civils
Moving from 10Gbps to 100Gbps to 400Gbps on the same dark fibre is a change of electronics, not a change of cable. So the carbon cost of upgrading is the kit at each end — not a new dig, new duct, new fibre.
Fewer redundant routes when diversity is real
A network that’s been properly route-audited at the design stage avoids the duplicate-build pattern (paying twice for “diverse” routes that share a duct, then paying a third time to separate them). Designed-in diversity costs less carbon than retrofit diversity.
Same fibre. Two jobs.
There’s a sustainability story that goes beyond the cable itself.
Dark fibre is increasingly used as the carrier for distributed fibre optic sensing — turning ordinary telecoms fibre into a sensor that can detect leaks, vibrations, intrusions, or temperature changes along its route. The cable doesn’t change. What changes is what we ask it to do.
On the OFWAT Dark Fibre 2 project, we provide the dark fibre that Focus Sensors’ IndusTM system uses to detect water leaks across networks operated by Severn Trent Water, Welsh Water, and Northumbrian Water. The wider goal of the OFWAT Water Breakthrough Challenge — what the £1.49m of funding is for — is a billion-litre-per-day reduction in UK water leakage by 2030.
Same fibre. Two jobs. That’s a different way to count the value of the asset.
Focus Sensors case studyAn honest list.
(This list is being confirmed with Richard at the post-build review. The Sustainability Guide PDF has the longer version.)
Designing for asset longevity — choosing routes and duct standards that extend the useful life of the cable
Designing diversity in at the start, not retrofitting it
Working with carriers and contractors who hold relevant environmental accreditations
Publishing the Sicom Guide to Sustainability — the longer version of the argument on this page
The current commitments list is illustrative — Richard will confirm the specifics at review.
A free download.
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