Ultimately, networks are no better than the access capacity that they provide to the end user, whether that customer is a business or a residence. Increasingly that access is through an optical link. The last decade has seen significant increase in the deployment of fiber in the access network, initially to the curb, but increasingly also directly to the business or home.
The United States is not a world leader in fiber to the home or business. It ranks roughly at number 11 among the countries in the world, with approximately 7 percent penetration. The penetration of fiber to the home in the United States is roughly 5 percent.4
Passive optical networks (PONs) are the primary broadband optical delivery architecture, providing the shared bandwidth of a fiber to multiple users (16 to 64 users). Initially, systems provided shared bandwidth of 2.5 Gb/s. New systems operating at a total bandwidth of 10 Gb/s are becoming available. Just as wavelength multiplexing has provided cost-effective bandwidth enhancement in long-haul and metropolitan networks, as capacity demand in the access network increases to enable new broadband services, it is expected that WDM will be employed for capacity expansion. A critical requirement will be robust, low-cost WDM optical components to operate in the outside plant. Research in this area at a somewhat modest level is ongoing; an example of U.S.-funded research in this area is the National Science Foundation (NSF) Engineering Research Center for Integrated Access Networks.5
In spite of the dramatic achievements that optics has brought to communication networks over the last decade (or, perhaps, because of them), the demand for higher bandwidth, both in the fixed and the mobile domains, continues to grow rapidly. Comparing projections from a number of sources, it seems conservative to suggest that network capacity demand will grow at the rate of at least a factor of 100 over the next 10 years, approximately following the recent historical trend shown in Figure 3.1.6 Ubiquitous video is the key driver. Increasingly that video is two-way as more end users upload video to sharing websites. Mobile video is also growing at an extremely rapid rate—92 percent compound annual growth rate according to a Cisco report7—that puts large bandwidth demand on the backhaul
4 Montagne, R. 2010. “Understanding the Digital World.” Presented at the FTTH Council Europe Conference. Available at http://www.ftthcouncil.eu/documents/Reports/Market_Data_December_2010.pdf. Accessed June 26, 2012.
6 Korotky, S.K., R.-J., Essiambre, and R.W. Tkach. 2010. Expectations of optical network traffic gain afforded by bit rate adaptive transmission. Bell Labs Technical Journal 1(4):285-296.
7 CISCO. 2012. “Cisco Visual Networking Index: Forecast and Methodology, 2010-2015.” White paper. Available at http://www.cisco.com/en/US/solutions/collateral/ns341/ns525/ns537/ns705/ns827/white_paper_c11-481360.pdf. Accessed June 26, 2012.