Multirate transceiver
Multirate transceiver in this case means the transceiver can support some bandwidth not only one bandwith. For easy to remember the keyword of multirate transceiver is the transceiver support from their bandwidth itself and below. Lets see the example :
SFP 1.25G (support multirate) = The SFP can support Bandwidth ? 1.25G
So this SFP can support bandwidth 1.25G (1G), 622Mbps (STM-4), 155Mbps (STM-1)
We make a list below so we can more understand :
SFP 1.25G can support SFP 1.25G (1G), SFP 622Mbps (STM-4), SFP 155Mbps (STM-1)
SFP+ 10G can support SFP+ 10G, SFP+ 8.5G, SFP+ 6.25G, SFP 4.25G, SFP 2.5G (STM-16), SFP 1.25G (1G)
QSFP28 100G can support QSFP28 100G and QSFP+ 40G
So if we have urgent situation we can use this scheme. Don't forget to check your equipment or ask your vendor, do they support flexible transceiver? (example use SFP 1G on 10G port or QSFP+ 40G on 100G port).
Please remember that we can't do opposite, like we use QSFP+ 40G to get 100G bandwidth or SFP 1G to get 10G Bandwidth. It can't work, since the chipset (machine) already build for only for 1G and 40G.
Last but not least, QoniTech transceiver 100% support multirate mechanism.