In the near future, broadband access networks will be required with data rates of over 1Gbit/s per customer. Currently, time-division multiple access passive optical networks (TDMA-PONs) are deployed. However, TDMA-PONs cannot keep up with the requirements for the broadcasting of a great number of HDTV channels and the unicasting of several triple-play services (voice, data and video). In contrast, wavelength-division-multiplexed PONs (WDM PONs) will be able to provide these required high data rates per user causing higher costs than with TDM-PONs. The introduced paradigm shift, at least one wavelength per service and user, leads to the introduction of new aspects in the design of future WDM PON access networks. In techno-economic evaluations, new network architectures with the highest potential concerning economic considerations have been identified. Access to these newly identified network architectures will prompt market introduction as well as market penetration helping Fiber-tothe- Home (FTTH) to become reality.
TopIntroduction
Due to the enormous and still rocketing bandwidth demand, there is no doubt that the age of Fiber-to-the-Home (FTTH) has arrived. The landscape of telecommunications, especially in the field of access networks, is now undergoing a major change towards FTTH. This major change is accepted worldwide and is driven by cutting-edge countries like Sweden, Korea, California, Japan, and projects like the Utah Telecommunications Open Infrastructure Agency (UTOPIA) in the USA or the Multi-Service Access Everywhere (MUSE) in the Netherlands and many other projects (Maeda, 2004; Lin, 2006).
Today, most Passive Optical Networks (PONs) and Point-to-Point (P2P) networks are being deployed only on a limited scale. Mass deployment of PONs was in its early stages. In Japan, Korea, Sweden, Denmark and Norway there were high levels of activities, while in the US and in other European countries the penetration and growth was more modest (Figure 1 a)). The countries in Figure 1 a) are sorted in ascending order by the total of broadband subscribers. In this context it is important to define the terms DSL, cable and fibre. In the terminology of the OECD (OECD, 2008), DSL includes all DSL lines offering Internet connectivity which is capable of download speeds of at least 256kbit/s. Cable includes all subscribers with a download speed greater than 256kbit/s. Fiber includes all fiber-to-the-premises subscribers at download speeds greater than 256kbit/s. In summary, only 1.1 broadband subscribers per 100 inhabitants over all OECD countries use fiber connections with at least 256kbit/s.
Figure 1. a) Broadband subscribers per 100 inhabitants, by technology, December 2007; b) average advertised download speeds, October 2007; (OECD, 2008)
In Figure 1 b), the average advertised download speed sorted by the same countries as in Figure 1 a) is shown. The arithmetic mean value of 13.7Mbit/s over all countries shows the poor bitrate compared with high speed passive optical access networks. Unfortunately, only a few exceptions like Japan, France, Korea and Sweden show significantly higher download speeds.
Figure 1 shows the significant lack of high-speed optical access networks in the world.