FireRepeater Converters are intended to convert between differnt transport media.
In DapTechnology's definition "Converters" are devices that change the tranport media (e.g. copper <-> copper) and the connectors can be either IEEE1394, LEMO, D38999, LC, ...
Be aware that DapTechnology refers to "Repeaters" (for same connector types) and "Adapters" (for different connector types) if the transport media remain unchanged.
Converters are very useful when the required distance exceeds the length that can be covered with copper-based wiring. Then the conversion into optical makes sense.
An example is shown below. Here a device-under-test (DUT) has to be connected to a FireMatrix system (9 bus) with the DUT located within an EMI Testing Chamber. The distance was too much to be covered with copper wiring. Additionally, a quite typical requirement is that the media converter needs to be very close to the DUT and is physically located within the test chamber, requiring the Converter to leave no EMI footprint and be battery powered.