Hi, I have an SFP fibre-optic tranceiver at 1.25gbit (Ethernet) and the receive output is connected directly to a SN65LVCP204 crosspoint. A crosspoint output goes to a Xilinx FPGA with PCs/PMA & MAC etc. If I loop back the FPGA output in the crosspoint it all works. UDP data packets are seen at the other end of the fibre using Wireshark OK. In other words, the Tx path is fine. The receive path, however, doesn't work. If I loop back the Tx fibre to the Rx input, the FPGA sees garbage. The Rx outputs at the crosspoint sit at the correct dc level ~1.5V and the signal seems to be OK but I haven't got any 1.25GHz 'scope probes to be sure.
The traces from SFP to crosspoint are about 2" and on impedance controlled inner signal layers with approximately equal lengths. The EQ pin is pulled up. What could be causing the problem? HELP! thanks
Dave
