Intrusion Detection Systems (IDS) may have an option to use a feature known as “Active Response” when malicious traffic is detected. If an attacker uses TCP sessions, they can be reset by RST (Reset) packets that are sent to reset one or both hosts in a session from the IDS. In the case of UDP, a session can be broken by sending various ICMP packets to the host from the IDS box.
In some cases the IDS may need to use the monitoring NIC for  this purpose. Enabling a Bi-directional traffic path in the tap allows the RST packets to renter the network through a tapped  copper link.  In the case of a tapped fiber link the directional characteristics of fiber taps will not allow this.  The “any-to-any” feature of Datacom Systems configurable taps allows the RST packets to be sent out any available extra Monitor  port of the tap and enter the network via a local network switch.
Traffic injection is only done on copper based inline taps or bypass switches.  Fiber taps do not allow traffic injection, based on their directional nature, they simply make a one way copy of traffic used for analysis.