Unfortunately it would appear the closest you are going to get is in the ifDescr MIB, but that will not give you serial numbers. It is not clear that serial numbers are even encoded in all SFPs; it depends on what the manufacturer puts in them. There are only a few actual optic manufacturers out there that sell SFPs. They sell to "manufacturers" who encode with whatever they want. Hence Cisco will sell you "cisco optics", HP "HP optics" etc but in reality, the underlying hardware is identical, just the extra "stuff" to make it unique. Serial numbers would need to be encoded by the "manufacturer" which most don't seem to do.
At least one manufacturer has digital diagnostics encoded in the SFPs which allow you to actually read things like receive & transmit power, temperatures, electrical power draws and even the serial number. Really useful information if you can see it and you are having issues. Unfortunately Extreme Networks is not one of them that does. It would really neat if they did however!
