Differential
Group
Delay
Fibercore
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Delay per kilometer of fiber optic cable
792 meters per microsecond (µs) or 3. In fiber optics, the latency of the fiber is the time it takes for light to travel a specified distance through the glass core of the fiber. 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. This reduction in speed is determined by the material's Group Refractive Index (n). When transmitting over. Light signals transmitted through fiber optics travel at approximately 200,000 km/s, which is slower than the speed of light in a vacuum (300,000 km/s) due to refraction in the glass material.