# Fiber Route Diversity A campus needs more than a fiber connection; it needs two that do not share a trench. Route diversity is the discipline of proving that the second path is genuinely separate, because the characteristic cause of a total communications failure is a single backhoe finding a single conduit carrying both of a facility's supposedly independent circuits. > [!note] The one-sentence version > Two circuits that share one trench are one circuit with extra paperwork. ## Why it exists Fiber is cut regularly, by excavation, by road work, by storms, and by agricultural equipment. A facility whose work must continue needs an alternate path that survives the event that took the first. The difficulty is commercial rather than technical: carriers lease capacity across each other's infrastructure, so two circuits bought from two providers may traverse the same physical conduit for miles. Diversity is therefore something to be audited rather than purchased. ## Prerequisites - **Dark fiber and lit services:** leasing the physical strands and operating your own equipment, against buying a managed circuit with a bandwidth and availability commitment. - **Conduit and right-of-way:** the buried duct and the legal permission for its route; the scarce assets in the whole business. - **Meet-me room and carrier-neutral facility:** the location where networks interconnect; proximity to one widens the choice of carriers. - **Diverse path and diverse entry:** separate routes across the landscape, and separate penetrations into the building, ideally on opposite sides with independent entrance rooms. - **Shared risk link group:** the formal designation of circuits sharing a physical structure; the correct question to ask a carrier. - **Latency:** propagation delay, roughly five microseconds per kilometer of fiber, plus equipment delay; it sets the floor on response time to a distant user. ## How diversity is established The buyer requires route maps, in detail, and compares them; demands a shared risk link group declaration; specifies diverse building entry with separate entrance rooms and separate conduit paths from the property line; and includes contractual notification if a carrier later re-routes a circuit, which happens. Where genuine diversity is unavailable, the honest answer is to say so and plan for the correlated failure rather than to assume a map is accurate. Many facilities add a third path, or a route in a different direction entirely, because two paths that both run along the same highway corridor are diverse only until that corridor is the problem. ## What latency buys Training is largely indifferent to distance; the work is internal to the cluster. Interactive serving is not: a user's experience includes the round trip, and a few tens of milliseconds are perceptible in conversation. That difference explains the geography of the industry, in which training campuses are sited where power is cheap and abundant while serving capacity sits closer to population; see [[wiki/Edge Inference|Edge Inference]] and [[wiki/Inference Request Routing|Inference Request Routing]]. ## Relationships - **required by:** [[wiki/Data Center Siting|Data Center Siting]] - **parallel discipline to:** [[wiki/Redundant Power Feeds|Redundant Power Feeds]] · [[wiki/Failure Domain|Failure Domain]] - **serves:** [[wiki/Inference Endpoint|Inference Endpoint]] · [[wiki/Edge Inference|Edge Inference]] - **built by:** [[wiki/Construction Sequencing|Construction Sequencing]] - **source articles:** [[articles/Vertically Integrating an AI Superpower from AI Factory to Citizen|Vertically Integrating an AI Superpower from AI Factory to Citizen]] · [[articles/The Gigawatt Is the New Measure of War|The Gigawatt Is the New Measure of War]] - **collection route:** [[collections/American Infrastructure|American Infrastructure]] · [[collections/American|American Collection]] ## Evidence posture - **Established:** fiber cuts as a routine occurrence; carrier capacity sharing producing apparent diversity over common physical paths; shared risk link group declarations as the verification instrument; diverse building entry practice; propagation delay on the order of five microseconds per kilometer; the latency indifference of training against the latency sensitivity of interactive serving. ## Sources - Telecommunications infrastructure and data center connectivity design practice, as current October 2026.