The best replacement for gpon is epon.

The best alternatives to gpon are rated as following:
★★★★★  epon
★★★★  gepon
★★★  active ethernet
★★★  bpon
★★  p2p
★  metro ethernet
★  hfc
  docsis 3.0
  rfog
  fttc
  docsis

Your alternative for gpon is not listed? Suggest!
Speaking about gpon, one probably shouldn't forget about mobile backhaul.

Other search terms related to gpon and their ratings are:
★★★★★ mobile backhaul
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Google Trends

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