Welcome lavayna,its great to help other members and share mutual knowledge.I would suggest you to go through paper i have attached in previous post.you will get to know basic idea and by reading system set part of these papers enable you to make HOA very easily in optisystem.All these paper implemented in optisystem and concentrate on Ranan and EDFa.Even then you will have any problem regarding these amplifier,we will help you for sure.
Cheers