Optical networks, Ethernet -- things are changing so quickly we barely have time to take it all in
September 1, 2000
This is the time of year when many of us will be taking well-deserved vacations. Some of us will be visiting an exotic far away place, while others (myself included) will be lounging in the backyard with a good a book. It is a good time to take a broad view of the evolution of information technology and how it is affecting our industry.
INFORMATION GROWTH SPURT
We are living in the information age where events are changing and information is growing faster than we can absorb it. Our success is measured not as much by how much we know but by what we know. We must therefore be selective and efficient in how we process and make use of that information.
Before I went on vacation, a colleague of mine paid me a visit. He had just bought a new laptop computer — an engineering marvel compared to the relic from the past (two years ago) that I am using today. The new machine has a 650 MHz CPU (more than four times faster than my 133 MHz Pentium), a 20 gigabyte hard drive (10 times the storage capacity of my hard drive), and a DVD drive for digital video playback. And it comes in a package that is broader, slimmer and only about one-half the weight of my current laptop.
What does this mean for the cabling industry? It means that the information will grow in proportion to the available capacity to store that information. It also means that the information by itself is useless unless that information is shared with someone. It creates an unprecedented demand for bandwidth for the transfer and exchange of information.
The key drivers in the market are the need for bandwidth and the need for mobility. Users want to be able to download large files without loss of time and productivity. They also want to be able to access their networks while traveling, while working at home or while attending a meeting. There are different technologies to transport information including copper, optical and wireless networks. Each technology has a significant place within the networking hierarchy. That is why it is important to consider different parts of the network separately, based on the type of information, the type of environment, distance limitations and the volume of traffic.
THE CABLING HIGHWAY
A good analogy of a cabling network is the system of roads and highways surrounding a major city. In order to move from point A to point B, the road system must be sized accordingly, without obstructions that create bottlenecks. From each business or residential location there are secondary roads, which feed into primary roads, which feed into major tributaries. These roads either lead into or from the city centre or bypass the city entirely for inter-city traffic. The size and construction of the roadways and the number of lanes of traffic are related to the capacity to support the volume of traffic. There are also alternate means to relieve congestion.
In a like manner, information networks are designed based on traffic considerations. The most efficient and cost effective means to transmit information for the last 100 meters is to use “high performance” twisted- pair copper cabling. The performance of copper cabling is recognized by TIA and ISO standards by its Category of performance.
Category 3 is a basic performance level comparable to a two-lane gravel roadway with a limited speed. Category 4 is now obsolete. Category 5 is a two lane paved roadway. Category 5e represents a better-maintained roadway with a faster speed limit. Category 6 would represent a roadway with twice the available capacity, e.g. a four-lane paved roadway. To ensure smooth traffic flow, all the components that comprise a cabling system (cords, cables and connectors) should be of the same or higher Category.
Optical networks represent the major highways and tributaries. They are designed to handle up to ten times as much traffic as the distribution roadways. For local area networks for distances up to two km., multimode fiber is typically used. It can support a wide range of applications that use LED (light emitting diode) light sources as well as LASER sources. The performance of multimode fiber is classified according to available bandwidth. Multimode fibers having a core size of 62.5 microns are typically used for backbone cabling. It has a bandwidth of 200MHz-km and can support a distance of 275 meters using 850 nm VCSEL lasers for gigabit Ethernet. For the same application, 50-micron multimode fiber has a bandwidth of 500 MHz-km and can support a distance of 550 meters.
The preferred choice today for a new installation is 50-micron fiber. For longer distances, usually for inter-building applications, single mode fiber is typically used. The bandwidth of single mode fiber is significantly higher and can support distances up to 40 km using high power lasers at gigabit data rates.
By the year 2003, it is envisaged that the IEEE will come up with a new standard for 10 Gb/s Ethernet transmission over optical fiber cabling.
While there have been major improvements in cabling performance over the last 10 years, we all know that we can expect more of the same in the years to come. It is certainly something to look forward to as you while away the hours of your vacation.CS
Paul Kish is a senior Product Manager, IBDN Systems & Standards at NORDX/CDT, Pointe Claire, PQ. He is also Chair of the TR-42 engineering committee.
Disclaimer: The information presented is the author’s view and is not official TIA correspondence.