Green field

Written on 2:32 PM by ooe

As mentioned in, green field (new-build) is a key problem area, which gives a focus to the problem of FTTH. New homes will incur the costs of civil works (digging) and outside plant anyway so the issue is which technology to install: twisted pair, coaxial cable or fibre, or a mixture of all three.

Green field fibre construction has been neglected because of the advance of broadband over DSL, cable modems and UMTS. Nevertheless, on a worldwide basis, there are significant volumes of new homes being built and even more homes requiring basic telecommunications services in developing nations.

The problem for system designers is to provide multiple-service capability: telephony, video and data. A rich service set allows a single fibre network to compete more effectively in economic terms with twisted pair and coaxial cable as the traditional means of delivering each of these services. None of these competes with fibre in terms of capacity and fibre offers more resistance to water ingress, lightning damage and electrical or RF interference. The opportunity for fibre systems vendors and operators is to make a single fibre more profitable than a bundle of wire pairs and coaxial cable for the delivery of multiple services. The full services access networks (FSAN) group was set up with this as the final goal. The activities of this and other standards bodies will be described later.

Providing traditional telephony services is troublesome over fibre because of the absence of wire for power feeding. Fibre is dependent upon the local electricity supply and batteries for back-up. Nevertheless, since this problem has been solved for cellular telephony, similar solutions can be used for fibre without incurring the additional cost of a copper access network.

There are numerous ways of providing video services. Both broadcast and switched are possible via PONs. The fibre infrastructure may carry broadcast services in all legacy modulation formats but time division multiplexing (TDM) offers opto-electonic simplicity and high power budgets. Pure TDM unfortunately is not a format used for video services in the mass market yet, although digitally encoded channels in TDM ‘bouquets’ are found in FDM broadcast systems. Such systems may come a close second best for transmission of broadcast video over fibre. Base-band switched video services direct to a PC are emerging via the Internet.

In the UK, although the franchises for cable operators expired in 2001, most green field build has remained a combination of twisted pair and cable. Twisted pair is provided to almost all locations, while cable is typically provided in the less rural areas. Fibre to the home has remained a niche application because of the continuing success of ADSL and the higher cost of fibre as explained earlier. Only in a few select trial areas has fibre to the home been deployed.

For BT, green field build has been a relatively low volume offering a limited opportunity for new infrastructure. However, there is expected to be a need for around 1 M new homes in the UK over the next decade with large developments in SE England.

A green field solution used by BT is TPON (telecommunications over a passive optical network) in remote cabinets or buildings. It has been narrowband only because of restrictions on cable TV services and an uncertain market for interactive broadband. In most cases the feeder to customers is copper pair rather than fibre.

So, despite the competitive environment that has been opened up since 2001, fibre to the home systems have remained difficult to justify, even in green field where the infrastructure costs are always encountered. This may change in the future as homes require data rates in excess of ADSL capabilities and more broadband services become available.

In the USA, the situation is similar; Telcos are beginning to compete with cable for multiple service provision. This competition is making incumbent operators think about radical restructuring of the access network to offer FTTH particularly in newbuild situations and there are a number of trial areas where FTTH has been used.

In mainland Europe and Japan cable operators and Telcos have followed separate evolution paths with separate licenses for cable TV and telecommunications and little competition between the two.