Hey there!
The Stack setup of CloudEngine series switches just requires ordinary service cables instead of dedicated stack cables.
Optical ports can be connected using high-speed cables, AOC cables, or optical modules+fibers. Electrical ports can be connected using Category 6A or Category 7 cables.
So, you can use optical modules+fibers to set up a stack.
Note:
10GE optical ports can be used for stack connections only when they have 10GE optical modules installed. They cannot be used for stack connections when having GE optical modules or GE copper modules installed.