Hi,
I have links which help you get more ideas about TWDM POn:
http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6289432
https://www.researchgate.net/publication/257774133_Key_technologies_and_system_proposals_of_TWDM-PON
https://www.osapublishing.org/jlt/abstract.cfm?uri=jlt-31-4-587
https://advanceseng.com/electrical-engineering/flexible-twdm-pon-wdm-overlay-converged-services/
http://www.journals.elsevier.com/optical-fiber-technology/most-downloaded-articles/
Thanks