Beyond a Threshold: Diminishing Resilience Gains from Additional Fiber Exit Paths Under Correlated Weather Disturbances

Telecommunication network resilience strategies frequently assume that increasing the number of geographically diverse terrestrial fiber exit paths proportionally improves availability and survivability. This assumption breaks down under correlated weather disturbances such as basin-wide floods, cloudbursts, landslides, cyclonic envelopes, and heat-driven failures, which can impair multiple routes simultaneously and constrain restoration access. This paper introduces an orthogonal risk-domain framing: resilience gains depend less on the number of terrestrial paths and more on the number of decorrelated Orthogonal Spatial Risk Zones (OSRZ) a geography can realistically support. Once OSRZ saturates—often around 4 in mountainous regions and 5 in well-connected central regions—additional terrestrial exits largely replicate existing risk domains and provide negligible improvement under widespread events. We conclude that seamless continuity of globally distributed Internet services requires a layered approach: (i) adding orthogonal risk domains such as OPGW/power corridors and satellite as an emergency layer, and (ii) weather hardening (“bulletproofing”) of both terrestrial and OPGW routes, since redundancy alone is limited by common-cause failures and correlated regional hazards.