which fiber-optic cable mode is used for long distances?

Provided that cables are installed correctly and kept protected from the elements, they should easily last for multiple decades . However, in practice, fiber optic networks are not always located in an ideal environment. A fiber optic cable’s actual lifespan should be at least ten years, but they will often last longer.27 Eki 2020

In general, these models give a probability of failure for any given fiber km over a chosen lifetime, of somewhere between 20 and 40 years . For correctly installed tier 1 fiber, the failure probability over such a timeframe is of the order of 1 in 100,000.

Fiber optic connections don’t degrade over distance , unlike cable broadband and DSL, allowing for consistent premium data transfer speeds. However, fiber optic connections also come with some limitations. Their high performance is pricey, cost of such service does limit range.