As a proponent of evaluating FttH topologies (shared and point-to-point) on their path dependencies and option values I have been looking forward to see how the Australians would make their choices.
One of the factors that make their case interesting is the utility infrastructure approach. The Australian Government has decided that a country wide open FttH infrastructure is required and will be deployed. Deploying FttH in vast countries like the USA and Australia poses its own challenges compared with dense urban countries like the Netherlands. Often citied issues are the lower densities of housing so a shared fiber architecture must be unavoidable, and very low density rural areas which are deemed unaffordable.
The recently published architecture of the Australian FttH network show an intelligent and interesting approach (courtesy Peter Ferris for explaining some details) . The first observation is that even in a vast country like Australia people live closely huddled on a small part of the land.
67 % Of the population lives in the top 50 urban areas, if you include the major rural areas you can reach 85 % of the addresses in 1,5 % of the land. So it makes sense to provide 93 % of the addresses with FttH and the remaining with radio (5%) and satellite (2%).
For the 93% which will get FttH they have chosen for a surprising combination of options in their architecture. The next-best-thing to full point-to-point in my opinion, full with potential to support different kinds of technologies and future upgrades if and when needed.
Let me focus on the interesting choices: overprovisioning in a point-to-point topology in the deepest part of the last mile, underprovisioning in the concentrated parts of the outside plant.
The basic building block of their architecture is a group of up to 200 addresses. A fiber local loop is deployed with 3 (!) fibers per address. In an aerial deployment 12 local drop fibre connectors (preterminated drop line, no splice needed) are made available on the poles per 4 addresses and used when and how required. The same approach is used for underground cabling. This setup will allow for layer 1 unbundling future expansion, support of point-to-point Ethernet to businesses, multiple ISP’s to same address, support for 3G/wifi mobile broadband and so on.
All fibers for these 200 addresses concentrate in a Fiber Distribution Hub (FDH), a cabinet in the street or cleverly combined with other uses like a seat in the parc. In the FDH the connections are made to either a splitter (for PON) or a single fiber (point-to-point) in ducts leading toward higher layers of the network. It is even foreseen to change the splitters for filters if WDM becomes financially viable.
Up to 16 FDH’s are concentrated into a Fiber Serving Area Module (FSAM, max 3200 addresses). The capacity in the concentration cabling initially deployed is enough to support PON as a technology to each home, plus some extra for businesses and other uses. Some sort of redundancy is built in by an interesting “dual-loop” structure by geographical separate paths in the connection of FDH’s to FSAM location. If needed the capacity to one or more FDH’s can be increased by deploying more cables in that path.
The FSAM is a planning construct initially but it allows also for future expansion. The number of addresses is ideally suited to be served by a prefab active equipment cabinet (know as Controlled Environment Vaults, or APOP’s in the Netherlands), if needed.
(Controlled Environment Vault)
These CEV’s bear a lot of resemblance to the prefab APOP’s Reggefiber deploys outside city centres. They can be truckrolled to a given location, placed within a day.
(Reggefiber prefab APOP)
At the start FSAM’s are just a passive concentration point for cabling to the Fibre Acces Node (FAN). Again some redundancy is introduced by geographical different routes for the cabling to the FAN exchange / central office, maximum size 76,800 locations/adresses.
It makes a lot of sense for the geography with lots of suburbanity. The key is having space in the street for these FDH cabinets. Just install a lot of point-to-point fiber in the part where a lot of labor is required (you don’t want to redo that ever) and allow for all kinds of upgrades , options for expansion, unbundling locations, active equipment deeper into the network, as you see fit in the future.
Smart guys, down under.
