Are you sure you have the right interface (eth1-01)? That is the error that ethtool -m will return if you target a non-fiber/non-SFP interface.
If it is the right interface, what driver name and version does ethtool -i eth1-01 show? It is possible the underlying NIC driver simply does not support that operation, or ethtool itself does not know where to find that info for that particular driver.
If it is the latter cause, you can try manually reading the various files under /sys/class/net/eth1-01, one of them might contain the SFP information you seek.
New 2-day Live "Max Power" Series Course Now Available:
"Gateway Performance Optimization R81.20" at maxpowerfirewalls.com