99% of the time, the problem is fiber polarity — specifically, Transmit (Tx) talking to Transmit and Receive (Rx) talking to Receive instead of Tx ↔ Rx. Good news: it's incredibly easy to understand and fix once you know the “two-lane highway” rule. In addition, fiber cables can transmit data over several kilometers without signal degradation, making them ideal for connecting switches in large campus networks and between different buildings. There are no specific requirements for this document. This includes Doppler. Fiber optic networks are celebrated for their speed and reliability, but even the best systems can encounter problems. Switch A is on the router end, devices connected to this switch get DHCP leases and can browse the internet without issue.