Failsafe in passive fiber TAPs

Passive fiber TAPs accomplish failsafe in a truly passive manner: no power is needed to pass traffic. Since fiber cables transmit light signals instead of electrical current, optical splitters are used instead of relays.

Diagram 7. Fiber breakout mode network flow

With a splitter, light coming in will travel through a prism and be split into two separate signals that are exact copies of each other. When light is split in this way, the signal will be reduced due to insertion loss. This loss of signal strength can be mitigated by selecting the appropriate split-ratio for the environment. Since splitters are only passing light, power is not required for the network ports to be directly connected to each other, effectively keeping the network links up, like there is not a device there.