Hello Durga,
Sam Sung gave a very important information about your question and, mostly, answered it. From my point of view, I would like to add that it is also good to check and follow the recommendations that has been issued for GPON. These recommendations are given by ITU-T as G.984-1,6. Please, see the following links for direct search:
https://www.itu.int/rec/T-REC-G.984.1/en
https://www.itu.int/rec/T-REC-G.984.1-200803-I/en