For many years people have talked about the wonders of optical fibers. Yet the dream of an all-optical network is far away from materializing. Fiber-to-the-Home (FTTH) is a reality in very few places around the world, in 2005 it represented less than 1% of total internet connections. The vast majority of people around the world is still using dial-up analogic connections, and the broadband users connect mainly through cable or xDSL (read copper). Below I investigate the Pros and Cons of Fiber Optics, trying to clarify why the technology is seen as the future of telecommunications and why, despite the advantages it offers, optical networks will require many years to develop completely.
- Bandwidth Capacity: optical signals can carry much more information than electrical ones. The most advanced copper cables can theoretically carry 1 Gigabit/second. Optical fibers, on the other hand, have a theoretical capacity of 350 Terabits/second or 350.000 Gigabits/second. Now that is the theory, what happens in practice? Current optical core networks (the backbone of telecom carriers) can already pack over 1 Terabit/second into a single optical fiber. The twisted copper pair (the cable that arrives to your telephone plug), instead, can transmit a maximum of 50 Megabits/second using the latest DSL technologies.
- Signal reliability: optical signals do not suffer electromagnetic interference and present a much smaller bit error rate compared to electrical systems. The signal loss (the amount of energy lost as the signal travels a medium) is also much lower in optical systems, meaning they can travel longer distances. DSL technology over the copper cable can cover up to 5 kilometers (18000 feet) before it needs a regeneration while an optical network can reach over 200 kilometers.
- Size and weight: the core of an optical fiber goes from 10 to 50 micrometers (1/5 the diameter of a human hair) while some coaxial cables have diameters of half an inch. The weight of 1 kilometer of optical fiber is about 6 kilograms while the same length of coaxial cable could weight as much as 1000 kilograms. When you need to roll-out networks long hundreds of kilometers having something light and thin can help.
- Cost per user: optical networks are the rule for carrier’s backbone because the huge amount of traffic justify the economic investments. Deploying fiber to the home, however, is a different story. Telecom operators spend around $ 1000 per fiber subscriber. If you then consider that DSL technology offers up to 50 Megabits/second (a reasonable bandwidth even for coming years) at a fraction of that cost you get the reason why FTTH is advancing slowly.
- Physical Constraints: optical fibers can not be bended too much or they lose some light reflecting properties. Additionally optical fibers can be damaged much more easily than copper cables, and the cost and complexity of the repair is significantly higher.
- Switching: current optical technology is very efficient for point-to-point data transmission. Unfortunately the same can not be said for traffic switching. Optical switching technology is advancing fast but it still can not match the flexibility and cost-efficiency of electrical switching solutions (read routers).
Summing up you can see that optical systems offer many advantages over traditional electrical networks and there is no doubt they represent the future technology for telecommunications. On the short term, however, optical networks will expand mostly into backbones and wide area networks. The last mile will continue to be dominated by xDSL technologies because they can leverage the wide installed base of copper cables, offering a reasonable bandwidth at much lower costs.