Why don t optical cables have electromagnetic interference devices

Fibre optic cables are immune to electromagnetic interference because they use light pulses to transmit data instead of electrical signals. Can someone go deeper into the subject? Optical communication are actually affected by strong EM fields, see. In this article, I explain how optical fiber is immune to EMI (electromagnetic interference) and how this impacts installations and networks located in areas of high electromagnetic interference and Radio Frequency Interference (RFI). The interference happens with coaxial cables but not with fiber optic cables as the signal. [pdf]