We specify the channel conditions allowed on a GMSL link between the SER and DES pair in the Channel Specifications document. The maximum length of COAX or STP cable that can be used determines on the RF characteristics of the PCB design, cables, connectors, and the temperature of operation. For automotive temperatures with Leoni Dacar cables and FAKRA connectors, we worked out an example on the first page of the datasheet for 15m. You may get longer distances if using lower loss cables/connectors, and operating to a lower temperature.
