I'm working on a project that involves transmitting data over very long distances (10-25km) where radio communication is unavailable, and I have been looking into the possibility of adding a fiber optic ethernet connection to the board.
The first issue I have run into is trying to figure out what specification I can or should be using. My first thought was to use
100BASE-FX sfp transceivers, and connect the other end to a TRENDnet TFC-110S60i which claims a maximum distance of 60km, however further investigation seems to suggest there is a 2km limit for
100BASE-FX connections. If my objective is to connect over these long distances, what specification should I follow?
The second issue I've run into is actually connecting a fiber optic transceiver, be it SFP or otherwise, to the controller. At this time no decision has been made for what controller will be used on the board, so I'm trying to select as generic an interface as possible. Unfortunately most chips I've found such as the Microchip KSZ8041 are only PHYs, or the Microchip KSZ8441 which uses a host bus that I am unfamiliar with how to implement. I've also found the Microchip LAN7500 which handles MAC and provides an SPI interface, but the documentation doesn't specifically say if
100BASE-FX/BX/LX/etc. is supported. Would I be able to connect this chip to an SPI socket on a circuit board, or do I need something that specifically says it supports a fiber ethernet format?