DP83867IR: Dose it support fiber i/f?

Hey John,

You are correct in that it isn't supposed to support fiber since the most reduced output it has for GigE is RGMII and then the flip side is MDI. Although far reduced from the 24 of GMII, it would be hard to put that over fiber without multiplexing.

I am going to guess that literature is wrong with two caveats: You can get fiber at GigE speeds if you use two PHYs and a different DP83867 series device.

So in order to even consider optical communication at GigE speed with this chip you will need to use the MII interface of SGMII, specifically the "4-wire" version where the clock is embedded so you only have one diff pair for Tx and another for Rx. Devices in the DP83867 family that support this mode end with CS, IS, and E - they can be found here.  

Now once you have two PHYs you will need to connect one to your MAC using whatever protocol you originally had in mind. Then connect the two PHYs together via the MDI interface so that they can bridge. Now with the bridge made, on the other side you will have a usable 1GigE signal in SGMII (assuming you've enabled it :/ ). This SGMII signal is just two high speed SERDES diff pairs so you can connect whatever you want to it, assuming sufficient drive. In this case it is a laser diode and photo diode. It is worth noting that you don't need to bother with magnetics for this MDI to MDI connection since they can both be on an impedance controlled board and you don't need surge protection.

Now you might be thinking, "I don't need gigabit operation, Nick". Well that's ok too! The DP83867 devices that support SGMII will actually transmit 100Mbps Ethernet too, it will just repeat each bit 10 times to compensate and will continue the 1Gig data rate.

If this answered you question please hit the green "Verify Answer" button below, I would really appreciate knowing I helped! If you still have questions just let me know and I'll  try to answer them for you.

Best Regards,

Nick