FTTH Network

Fiber and Bandwidth


Q: What is bandwidth?
a: In a network, bandwidth (what engineers call bitrate) is the ability to carry information. The more bandwidth a network has, the more information it can carry in a given amount of time. Networks with high bandwidth also tend to be more reliable because fewer bottlenecks disturb the flow of information.

Q: How much bandwidth – or information delivered by bandwidth – do we need?
a: The amount of bandwidth we need grows every year. Worldwide bandwidth use roughly doubles every two years. The biggest growth has been for video – traditional pay TV, “over the top” or Internet-based video, and video communications. This trend is expected to continue; Cisco estimates that by 2017, consumer Internet video traffic will account for 69 percent of all consumer Internet traffic, up from 57 percent in 2012. Video requires not only extra bandwidth but also extra reliability. The smallest delay in data transmission can result in distorted views. More video is available than ever before, and people are watching video on more screens at once. In addition, video formats are becoming more bandwidth-intensive. HDTV can require 8 megabits per second (Mbps) or even more for fast action such as in sporting events, even with new MPEG-4 compression technology. So-called 3D immersive HDTV – already used in some academic and industrial settings for telepresence – requires between 50 Mbps and 300 Mbps, and 4K video, which has four times the pixels of today’s best-quality HDTV broadcasts, requires 16 to 32 Mbps, depending on how fast the screen action is and how much of the screen is taken up by fast-moving objects.

Q: What about other kinds of data?
a: Bandwidth requirements for many kinds of data are exploding. For example, new digital cameras can create larger and larger images; 30 megabytes is not uncommon.Amateur HD video cameras use about 10 gigabytes per hour of video – the equivalent of 300 of those 30 MB still images. In health care, the medical images produced by equipment such as CT scanners are a hundred times larger than camera images, and more. In the last few years, business and science both entered the era of “Big Data” applications that collect and analyze data on massive scales. Today’s Big Data applications range from consumer pricing models to DNA sequencing to particle physics to control of electrical grids. Big Data doesn’t work without Big Bandwidth. A DNA sequencer produces enough data to monopolize a 2.5 Gbps connection.

Q: Can’t copper carry high bandwidth?
a: Copper’s capacity is far less than fiber’s. It can support high bandwidth for only a few hundred yards. The longer a signal travels on copper, the lower the bandwidth.

Optical fiber is unique in that it can carry highbandwidth signals over enormous distances. Fiber uses laser light to carry signals. Under some circumstances, a signal can travel 60 kilometers (36 miles) without degrading enough to keep it from being received. The
international minimum standard is 20 kilometers (12 miles). Fiber is also far better able to support upstreambandwidth – that is, from a user to the network.

Q: What’s the difference between upstream and downstream bandwidth, and why is it important?
a: In the debate about FTTH versus copper-based broadband, people tend to argue in terms of downstream bandwidth because most users need more downstream bandwidth than upstream – especially for bringing video entertainment into the home. But emerging consumer uses such as home video uploads, computer games, distance learning, video communication and telemedicine may require as much upstream bandwidth as downstream. Small businesses, often home-based, may need upstream bandwidth as well – imagine a wedding photographer sending proofs by email to clients. Larger businesses may wish to copy all their working data files for safekeeping to a remote computer center.

Q: What about wireless? i hear 4G wireless can provide 54 Mbps.
a: That’s the potential bandwidth shared by all users connected to a cellular antenna. Wireless broadband depends on fiber to move information to and from cell towers. Even so, each antenna can support only a finite number of cellular signals. Cellular data traffic grew 200-fold from 2006 to 2012 and will grow another eightfold by 2016. Providers are now severely limiting wireless data, encouraging or forcing customers to use Wi-Fi connections instead of cellular networks for data. Those Wi-Fi connections, in turn, work best when they can quickly offload data to a fiber network. A typical cellular data plan allows 5 gigabytes per month. Use your phone to view video, and you quickly run over the limit.

Q: What exactly makes fiber “future proof”?
a: The equipment used to send light signals over glass fiber keeps getting better. So equipping an existing fiber network with new electronics and with lasers that pulse light faster, or lasers that use different wavelengths of light, can vastly increase available bandwidth without changing the fiber itself. New electronics are very cheap compared with the original cost of laying the fiber. At the customer end, the system can be designed so that customers themselves can simply pull the old unit out and plug the new one in. Therefore, once fiber has been deployed, network operators can keep increasing bandwidth as needed at very little cost.

Q: How long has fiber optic technology been in use?
a: Fiber optic cable is the foundation of the world’s telecommunications system. It has been used for more than 30 years to carry communications traffic from city to city and from country to country. Almost every country has some fiber optic cable, delivering services reliably and inexpensively. The first time fiber delivered a signal directly to a home (in Hunter’s Creek, Fla.) was more than 25 years ago. Today, more than 200 million homes worldwide have fiber connections available, and more than 100 million homes are connected to fiber.

Q: all providers seem to claim they have fiber networks. What’s different about fiber to the home?
a: Don’t be fooled! It is true that most cable and FTTN (DSL) networks use some fiber. In these networks, the fiber carries the signal close enough to homes so that copper can carry it the rest of the way. However, this approach requires expensive, difficult-to-maintain electronics at the point where fiber meets copper. (These electronic devices use a great deal of power and are quite sensitive to lightning strikes. Even the cost of bringing electric power to them can be huge, depending on where they are located.) The available bandwidth is far less than in an all-fiber network. And most of these halfway approaches do not allow symmetrical bandwidth – cableand DSL systems generally can’t upload information asfast as they can download it.

Q: isn’t a network with some fiber good enough?
a: It may be fine to send emails, download songs or share family photos. If you want to log on to the corporate LAN from home and work effectively, or run a homebased usiness, you’ll need more. And what about uploading a high-def video of your child’s football game, or sitting down to dinner virtually with family members a thousand miles away?

Q: Why does it matter how close to the home fiber comes?
a: With copper cable, bandwidth drops precipitously with distance. The most recent expedient, vectored DSL, allows 50 Mbps downstream signals for as far as 1,800 feet under ideal conditions. It won’t work on very old copper wiring, its upstream bandwidth is limited and it requires expensive electronics. However, it is touted as an interim solution for network builders that cannot afford FTTH. In the next few years, a new technology, G.fast, will become available; under ideal conditions and with vectoring (crosstalk cancellation), G.fast is expected to provide 500 Mbps symmetrical bandwidth up to 300 feet from the node. G.fast may prove to be an excellent solution for retrofitting apartment buildings with fiber to the basement (as long as those buildings have good internal wiring), but it requires bringing fiber very close to customer premises and is still limited in comparison with true fiber to the home.

Q: With cable and DSL, there’s often a gap between advertised and actual bandwidth. is that true for fiber?
a: No. Cable, DSL and even wireless networks are usually heavily oversubscribed – that is, providers promise users more than the total amount of available bandwidth because they know all users aren’t going full throttle most of the time. As a result, networks slow down during periods of heavy use, such as when teenagers come home from school. Copper networks are also more subject to speed degradation due to the condition of the wiring. Fiber has enough bandwidth and reliability that providers can guarantee high speeds with little or no over subscription. If a fiber network is designed properly, users will always get the speeds that are advertised – or better. Data published by the FCC in February 2013 showed that, on average, fiber-to-the-home services delivered 115 percent of their advertised speeds.

Q: is FTTH technology expensive?
a: In new construction, fiber costs about the same as copper to build, and it costs much less to operate and maintain. Building fiber to the home is expensive only when compared with not building a new network – that is, with making minor tweaks to an existing copper network. The problem is that these less-expensive solutions don’t meet users’ needs. In the last few years, the flood of video content has outrun the ability of older copper technologies to handle bandwidth demands. In many parts of the world, providers shut off or slow down service or impose prohibitive fees for customers who exceed monthly bandwidth caps. Customers don’t like
these restrictions, and they don’t appreciate being called “bandwidth hogs” for using services they have paid for. In addition, it’s not clear that providers save money by failing to meet users’ needs because limiting bandwidth
means limiting revenue potential as well.