How Fiber Latency Is Calculated: Propagation, Equipment and Serialization Delays

This technical explainer breaks down how to estimate fiber-optic latency using a model that sums propagation time, equipment delay, and serialization delay. Route length is derived from a distance and a route factor of at least 1, then multiplied by the group index, which governs how fast a modulated pulse travels through glass. Equipment delay is a fixed per-device value multiplied by device count, while serialization delay is the time to clock a frame onto a link across a set number of hops. One-way delay is the sum of these terms, and round-trip time is twice that figure, with queuing and error correction deliberately excluded. A worked example of 100 km at the default group index of 1.468 yields a one-way propagation delay of about 489.67 microseconds and a round-trip time of about 979.34 microseconds.