Exceeding the maximum transmission distances can result in significant signal loss, which causes unreliable transmission. An optical data link functions correctly provided that modulated light reaching the receiver has enough power to be demodulated correctly. The uses various types of network cables, including multimode and single-mode fiber-optic cable. It is the power attenuation of the signal after. To be able to judge whether a fiber optic cable plant is good, one does a insertion loss test with a light source and power meter and compares that to an estimate of what is a reasonable loss for that cable plant. It is a natural phenomenon that occurs for any type of transmission—whether it's electricity or data.
