Hi Sulaiman,
The exact coding choice you want to use will change the gratings used, for example the Hadamard or Walsh code which is what I am most familiar with has codewords of length 2^k, so 4, 8 etc. The number of users that it is optimized for is one less than the codeword length, so 3 and 7. I don’t believe a 5 User FE-OCDMA Hadamard is a common system, but you could make it by simply removing two users from our 7 User example we have.
If you have a different code word scheme just let me know the code words and I can make it quite simply.
Regards