Temporal delays or latency in optical fiber refer to the time it takes for a light signal to travel a certain distance from the source to the receiver. Despite the high data transmission speed, the signal does not propagate instantly and requires time to cover the distance. This. Latency is a term that is used to describe a time delay in a transmission medium such as a vacuum, air, or a fiber optic waveguide. 792 meters per microsecond (µs) or 3. In fiber optics, the. Subsea fiber optic links carry most intercontinental internet traffic, so even small changes in route length or signal speed can matter.