The company Strukton has developed their own discrete transceiver circuit for a WorldFIP cable. This may be used instead of a FielDrive component. The FielDrive has other functions like error detection and timers that are not implemented in this circuit. The circuit, that is field proven since 2012, is made available as Open Hardware with the CERN-OHL-P v2 licence.
It has been designed for the 1 Mbps speed, and likely it will work with 2.5 Mbps.
Theoretically it should also work at a speed of 31.25kbps. The transformer could just about handle that with its volt-second specification (but still should be tested).
No other documentation of this circuit is available.
FIP-port, an alternative 1 Mbps WorldFIP transceiver circuit
Copyright Strukton 2023. This source describes Open Hardware and is licensed under the CERN-OHL-P v2.