SPF+ is fixed speed module and we cannot change it speed I agree.
What I want to know is data transfer rate on fiber link installed on SPF+ can be anything between 0 to 10Gb?
I mean in peak hours data transfer rate can go 8 or 9 Gb on the link and in out of office hours data rate even can go 1G or less than it
SPF+ module can support all data transfer Rate from 0 to 10Gb on the fiber link.