[amazon_not]

> Fiber like GPON is shared physically-ish, but DWDM isolates individual waves so thoroughly that it's hard to think of that as a shared physical medium unless you're thinking about backhoe fade and the like.

This is incorrect. GPON does not use DWDM, or any individual waves per subscriber. GPON is a shared medium with one wavelenght used in the upstream and one wavelenght used in the downstream direction. Each subscriber is allocated bandwidth on the shared medium.

Not even next generation PON uses DWDM. Next generation PON still uses on upstream and one downstream wavelenght per PON tree, but there can be multiple PON trees on the same backhaul fiber. It's more like a CWDM overlay of PON trees.

The only PON that uses DWDM is WDM-PON, but it isn't deployed commercially at scale yet.

[oasisbob]

Thanks for the correction - easy to forget that the P in PON is for passive.