3 ms·

Depends on the market. If you're in a high density area the cost of feeder fibres is inconsequential. If you're in a low density rural market, additional feed

by bcrl 3y ago

Depends on the market. If you're in a high density area the cost of feeder fibres is inconsequential. If you're in a low density rural market, additional feeder fibres are expensive. Smaller market players can't get the 30 year amortization that governments can which makes cost matter. The optical signal budget in a Passive Optical Network (PON) is a function of the split ratio (commonly 1:32 => 2^5 => 5 * 3dB = ~15dB) and distance involved (typically 0.35 dB/km), which both are a function of the network design. Passive optical networks are typically designed around a 20 km distance with a 1:32 (sometimes 1:64 for 10G PON variants) splitter ratio. You can trade splitter ratio for distance if needed. An 80km DWDM optic is tight at the extreme distance, but 120km is pretty close to the 1:32 / 20km link budget. My point is that it is viable to overlay DWDM on a network designed for PON.

midasuni 3y ago
Is the cost of a single core with a 32 way splitter really a lot cheaper than a 32 core cable?
- bcrl 3y ago
  A 1x32 splitter costs somewhere between $20-70 (unless you pay exorbitant Corning prices). 32 core (well, 36 core) cables are cheap enough, but that's not what you need for a pure point to point network. Let's say you've got a local convergence point with 576 fibres facing the distribution network. With 1x32 splitters you need 18 feeder fibres. You can get a 24 core cable for $350/km. Now, let's say you're building a fully point to point network. You now need a 576 core cable for your feeder in the access network. That's going to cost north of $6000/km (that's a wild guess -- sorry, I don't have accurate numbers for high count cables as I haven't bought any in the past few years). If your access network is 10 km, that's the difference between $3,500 in cables vs $60,000 in cables. Plus you're adding a good $1,500-3,000/km in cost for larger splice closures and increased splicing labour. Where it really hurts is when you start getting close to your Central Office (CO). With P2P networks, you need more larger cables in the first few kilometers closest to the CO, which is often the most congested part of a network. For brownfield builds, that might require directional boring to install new conduit in a town to bring the new cables into the CO. That can get really expensive. Designing fibre networks is a game of whack-a-mole. Spending less on one component drives up costs on other components. Sure a P2P network means you can use cheaper SFPs, but the outside plant is more expensive. There's good reason that most carriers are building Passive Optical Networks -- P2P just isn't economically viable in all scenarios.
  - matt-p 3y ago
    These maths are quite theoretical! In reality in a 1:32 PON you'll typically use somewhere between 14 and 30 ports (because typically you want to leave at least one spare port). In rural areas the lower side of that is more likely as your splitter placement will be governed by how far apart properties are. 864f cable which is the biggest you'd realistically blow is about 11mm diameter, and costs around £9/metre. If in the PON situation you're blowing say 72f for £1/metre then your costs are honestly not that much higher, considering you don't need to have lots of splitters all over the place (often you have actual passive splitter cabinets, as putting them in chambers is not always possible) you may need a bigger splice joint but not really much bigger because you're now using ribbon fibre. The number of splice operations would be similar too. Obviously this doesn't scale super well, but we are discussing rural subsidised fibre here, not low cost competitive urban deployments. The likelihood is 864f is more than enough for a whole village, or even several. If not add a second.
    - bcrl 3y ago
      Yes, but you don't plan your network based on actual capacity usage, you plan for a fully loaded network that can serve 100% of dwellings passed along with some spare capacity to serve additional buildings over the expected lifespan of the network (30+ years if you're building an expensive incumbent network, 5-10 years if you're trying to minimize cost). Anything else means you could end up turning customers (revenue) away.
- deleted 3y ago
  [deleted]
matt-p 3y ago
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.

by bcrl 3y ago

midasuni 3y ago

Is the cost of a single core with a 32 way splitter really a lot cheaper than a 32 core cable?

bcrl 3y ago
A 1x32 splitter costs somewhere between $20-70 (unless you pay exorbitant Corning prices). 32 core (well, 36 core) cables are cheap enough, but that's not what you need for a pure point to point network. Let's say you've got a local convergence point with 576 fibres facing the distribution network. With 1x32 splitters you need 18 feeder fibres. You can get a 24 core cable for $350/km. Now, let's say you're building a fully point to point network. You now need a 576 core cable for your feeder in the access network. That's going to cost north of $6000/km (that's a wild guess -- sorry, I don't have accurate numbers for high count cables as I haven't bought any in the past few years). If your access network is 10 km, that's the difference between $3,500 in cables vs $60,000 in cables. Plus you're adding a good $1,500-3,000/km in cost for larger splice closures and increased splicing labour. Where it really hurts is when you start getting close to your Central Office (CO). With P2P networks, you need more larger cables in the first few kilometers closest to the CO, which is often the most congested part of a network. For brownfield builds, that might require directional boring to install new conduit in a town to bring the new cables into the CO. That can get really expensive. Designing fibre networks is a game of whack-a-mole. Spending less on one component drives up costs on other components. Sure a P2P network means you can use cheaper SFPs, but the outside plant is more expensive. There's good reason that most carriers are building Passive Optical Networks -- P2P just isn't economically viable in all scenarios.
- matt-p 3y ago
  These maths are quite theoretical! In reality in a 1:32 PON you'll typically use somewhere between 14 and 30 ports (because typically you want to leave at least one spare port). In rural areas the lower side of that is more likely as your splitter placement will be governed by how far apart properties are. 864f cable which is the biggest you'd realistically blow is about 11mm diameter, and costs around £9/metre. If in the PON situation you're blowing say 72f for £1/metre then your costs are honestly not that much higher, considering you don't need to have lots of splitters all over the place (often you have actual passive splitter cabinets, as putting them in chambers is not always possible) you may need a bigger splice joint but not really much bigger because you're now using ribbon fibre. The number of splice operations would be similar too. Obviously this doesn't scale super well, but we are discussing rural subsidised fibre here, not low cost competitive urban deployments. The likelihood is 864f is more than enough for a whole village, or even several. If not add a second.
  - bcrl 3y ago
    Yes, but you don't plan your network based on actual capacity usage, you plan for a fully loaded network that can serve 100% of dwellings passed along with some spare capacity to serve additional buildings over the expected lifespan of the network (30+ years if you're building an expensive incumbent network, 5-10 years if you're trying to minimize cost). Anything else means you could end up turning customers (revenue) away.
deleted 3y ago
[deleted]

matt-p 3y ago

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.