The physical layer of cyberspace is comprised of physical elements, from fiber optic cables to cell towers, to computers and servers. Of chief importance are the fiber optic cables that traverse the globe, overland and undersea, and transmit data packages from one location to another. In addition to these cables, there are physical nodes of cables (where cables come together) called Internet exchange points, as well as server farms that centralize the processing of data packages and route them to their final destination. Additionally, satellites essential to government and commercial communications exist, although they transmit only a small fraction of the information that flows through cyberspace. Lastly, the electromagnetic (EM) spectrum is a constituent part of cyberspace – essential to its functioning and basic operations.

CABLES

Submarine Cables

Submarine cables traverse ocean, sea, and lake floors, carrying about 95 percent of all intercontinental telecommunications traffic in the form of voice and data. International banking and finance activities are highly dependent on these cables, as are the government and military. Data and voice communications can be passed via satellite, but it is significantly less expensive and faster to use fiber optic cables. These cables are the fibers that hug the globe and underpin the modern telecommunications system.

There are approximately 1.197 million kilometers of undersea cables. There are 291 in-service fiber optic cables around the world. The longest cable systems connect continents, while shorter systems are laid along coastlines to avoid the problems of terrestrial cables and provide additional resiliency. The highest concentration of cables connects the east coast of the United States with Europe and the largest-capacity cables connect New York and the United Kingdom. Figure 3.1 shows the location, routes, and end points of submarine cables around the world.

Most submarine telecommunications cables are fiber optic cables, especially newer cable systems. The older coaxial cables are still in use in some places, but their bandwidth capacity is much more limited. Fiber optic cables have become the primary cable used due to increased demand, changes in technology, and reduced cost.