As a common engineering estimate, 1 kilometer of fiber adds about 5 microseconds of one-way propagation delay, or about 10 microseconds round trip. 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. In free space, light travels at 299,792,458 meters per second. As a result, one-way delay increases linearly with distance, making total cable length the most. The fiber latency calculator helps determine the time it takes for data to travel through a fiber optic cable between two points. When transmitting over. In fiber optical networks latency consists of three main components which adds extra time delay: opto-electrical components.