Dark fiber gets sold on one number. Dollars per strand mile. That number is the one everybody argues about. It is also the least important line on the quote.
The real cost hides in three places. The O&M fee. The lateral build. The term structure. Most buyers negotiate the strand-mile rate hard and sign the rest as written. That is backwards. A buyer who cuts the strand rate 20 percent but accepts standard O&M and relocation language usually pays more over the term than one who paid list and fixed the other terms.
Here is how to read the whole quote.
Three ways to price it, and why quotes don't line up
Dark fiber comes three ways. A 20 year IRU with a big upfront charge. A monthly lease, usually 5 to 10 years. Or a hybrid, lower upfront plus a monthly fee. You cannot compare a Zayo IRU to a Crown Castle lease until you convert both to a 20 year all-in cost per strand mile. Do that first. Then line up Lumen, Uniti, and your local muni or electric utility on the same sheet.
The 2026 ranges by market
These are list bands before you negotiate. Route and strand count move them a lot. Confirm against live quotes.
- Dense tier-1 metro (NYC, Chicago, Dallas, Bay Area): roughly $1,500 to $3,500 per strand mile on a 20 year IRU. $150 to $400 per strand mile a month on lease.
- Tier-2 and tier-3 metro (Kansas City, Nashville, Columbus): roughly $800 to $2,000 IRU. $75 to $200 a month lease.
- Long-haul between cities: roughly $300 to $900 IRU. $20 to $75 a month lease, with volume breaks past 100 miles.
- Rural or single-provider routes: often higher per mile than tier-1 metro. No competing route means no pressure on price.
What drives the spread? Existing route versus new build. Aerial versus underground. How many carriers run the same path. Strand count. And whether you buy as a carrier or an enterprise. Carriers routinely pay 30 to 50 percent less than enterprises on the exact same route.
The line items that aren't on the strand-mile number
Now walk past the headline.
O&M, the yearly maintenance fee, runs about $50 to $150 per strand mile per year on an IRU. It usually escalates 2 to 3 percent a year. Over 20 years that can equal 10 to 20 percent of the IRU price. This is the most negotiable recurring fee in the deal, and most people never touch it.
The lateral is the last few hundred feet from the carrier's route into your building. It runs $25,000 to over $150,000 depending on aerial, bore, or trench. On a short metro pair, this is often the single largest number on the quote. Splicing runs $1,500 to $5,000 per splice point. Then colo, cross-connects, meet-me-room fees, and right-of-way pass-throughs.
And relocation. When a DOT or utility forces a route move years in, who pays? Standard carrier paper puts it on you.
On a 15 mile metro pair, the non-strand-mile costs often total more than the IRU itself.
The terms that change the 20 year math
Fix these before you sign. An IRU survives carrier bankruptcy in a way a lease may not. Make the renewal an option at a nominal fee, not a renegotiation. Pin the restoration SLA, 4 hours or 8, and ask about credits (most dark fiber paper has none). Get the fiber spec in writing, G.652D with a dB/km attenuation guarantee, or your 100G optics may not light the route. Get the no common conduit rep in the contract, not just on the call. Keep assignment rights so the strands have value if you move or get acquired. And cap the O&M escalator with a right to self-maintain after year 10.
When a lit wave wins
Dark fiber only wins when you need multiple 100G waves on the same route, you have a 10 year horizon, you have engineers to run optics, and the lateral is cheap or already built. Otherwise, buy a wave. In 2026 a 100G wave on a metro route commonly runs $1,500 to $4,000 a month. A 10G wave runs $600 to $1,500. A 10G Ethernet transport circuit often lands under $1,000.
The common failure: a company buys dark fiber for a single 10G need. Then it spends more on optics, O&M, and staff time than a wave would have cost in a decade.
How to run the quote
Pull three quotes on the exact same A and Z addresses and strand count. Require each to itemize NRC, O&M, lateral, splice, colo, and relocation separately. Ask for the carrier rate card as a reference. And call the muni or electric utility. They often own the cheapest route and never show up in a search.
Then make three asks. O&M capped at a fixed dollar figure, no percentage escalator. Lateral amortized into the term or waived for a 20 year IRU. Relocation capped or carrier-borne for the first 10 years.
Build a single sheet. Every line, 20 years, all in. Run the same math on a lit wave for the same route. Most readers find they should buy a wave. The ones who should buy dark will save more on O&M and relocation than they ever would on the headline rate.