The FIB2-Serial operate in pairs with a fiber link between them. When they are is set to RS-232 5-Wire mode, the pair provides transparent signal and flow control between the two units and can act as DTE or DCE depending on the direction of the data and flow control. The following should give a better idea of the way the link works.

                   +----------+        +----------+
RS-232 data(IN) -->|          |        |          |--> RS-232 data(OUT)
                   |          |        |          |
RS-232 data(out)<--|          |--------|          |<-- RS-232 data(IN)
                   | FIB2     | fiber  | FIB2     |
Flow Ctrl(IN)----->|          |--------|          |--> Flow Ctrl(OUT)
                   |          |        |          |
Flow Ctrl(OUT)<----|          |        |          |<-- Flow Ctrl(IN)
                   +----------+        +----------+

The flow control signals can be of your own choosing. For example, send a RTS signal at a flow control in and on the other side out of the fiber link take the resultant flow control and send to CTS. Using the above scheme, you can provide one hardware flow control signal in each direction.