This is really not true in practice. 1:32 split gpon in theory can do upto 20KM but in practice with a typical number of splices, reasonable optical budget and

This is really not true in practice. 1:32 split gpon in theory can do upto 20KM but in practice with a typical number of splices, reasonable optical budget and so on you are looking at maybe 15KM. 1:64 xgspon is really only good for about 6km. Cost differences between PON and ptp are minimal in fibre plant typically £5-40; the money you save on spine fibre is mostly lost on splitters and space for them. The real savings in PON comes from head end kit (OLT) and resulting power and space savings. In practice with a mix of 32 and 64 splits port and power costs at the head end is about a tenth of p2p. Of course you make sacrifices in return for that. Regarding your point on DWDM, it's technically possible on good quality PONs with very high power optics but it would have to be with MACSec or similar as you are giving the signal to everyone on the PON to receive! The costs of this plus optics, dwdm mux/demux and so on makes this a frankly laughable proposition. This is fundamentally the point. You can't really provide business services such as leased lines or mobile tower backhaul over a PON. In this circumstance you'd have to give a PON to each service provider. This architecture doesn't really economically work for layer 1 fibre wholesale access, you'd realistically need to have the wholesale provider run the OLT and ONT and give each wholesaler layer 2 access to each customer. So for example you may be stuck with GPON (on openreach) like we are in the UK. This debate was had at the time between ofcom and Openreach here and layer 2 access was deemed acceptable. Several years later, they had to force them to provide duct and pole access and in some cases dark fibre (for business and backhaul use in areas with no competitors). The former was mostly because openreach were too slow to rollout even thier PON solution, so we now have a situation in some areas where as many as half a dozen ISPs have installed thier own fibre all the way into each persons flat/house. Would it have been better to let a contract for p2p fibre install in rural areas rather than subsidising openreach on a PON and then in some cases have a commercial fibre provider build over that unsubsidized. Yes, no doubt.