How it Works

Fiber Optic Cables

            A fiber optic cable is a direct link through which it connects one country to the rest of the globe for voice and data transmission. There are land as well as underwater connections all over the world, linking countries through a network of fiber optic cables. Majority of the world’s telecommunications and Internet traffic flows through these network of cables. The submarine fiber optic cables are laid along the seabed between land-based stations. These cables carry telecommunication signals across the ocean; carrying telephone, internet, and private data traffic.(2)

            A standard fiber optic cable contains one or more optical fibers. The fibers are coated by plastic layers and contained in a protective jacket depending on the environment the cable will be placed.(9) The submarine fiber optic cable contains the same components as a land cable, except it has more protection. Displayed in Figure 1, it contains the optical fibers, petroleum jelly, copper or aluminum tube, polycarbonate, aluminum water barrier, stranded steel wires, mylar tape, and a polyethylene protective jacket.(11)

            Submarine fiber cables are laid under the sea at 8000 m, where the seabed is rocky and the pressure is extremely high. There is a negative effect of hydrogen on the optical fibers over time. The 17 mm cable has a typical volume and weight of 3.5 km/m^3 and 2 km/ton. As seen in Figure 2, it has a range of protections; double armored, single armored, lightweight protected, and lightweight. These protections will keep the optical fibers safe at a depth of 8000 m in various seabed conditions.(1)

Submarine Cable Technology

           Submarine cable systems offer very high capacity up to 2 Tbps per cable. They have real time transmission along with very low bit error rates. The submarine transmission is known for having the best security of transmission. Submarine systems have optically amplified repeaters which are all photonic, meaning that no electronics exists in their transmission path. This allows for the simpler repeater construction to have a bit rate free from modulation and to use only low speed electronics. Pump lasers are the main components of a repeater, which remain protected on a 1 + 1 basis to cope with possible component failure.(1)

           System performances are monitored from the submarine line terminal station by modulating a very low-level signal onto the carrier. The signal is looped-back through a special high loss optical loop-back coupler at each repeater. The terminal then determines the gain performance of each individual amplifier in the system. This is done by recovering low-level signal  as returned by each successive repeater and comparing different levels.(1) Forward error correction is used for controlling errors in data transmission and essentially providing error-free performance of an increase in the system bit-rate.(7)

           Wavelength-division multiplexing (WDM) can transmit multiple optical carrier signals on a fiber pair by using different wavelengths. These wavelengths are sent down branches to their expected destination using wavelength filters. WDM provides full mesh connection by wavelength and facilitates the allocation of dedicated wavelengths between two specific nodes. WDM can also be upgraded by adding more optical channels without additional fiber. The multiplexing of several wavelengths on the same fiber allows 16 x 2.5 Gbps of information to be carried throughout the oceans.(13)

Transatlantic Cable Network

            The Transatlantic cable network runs under the Atlantic Ocean. As of 2012, there are a number of implemented transatlantic cables, both TAT and private non-TAT. There are currently two private non-TAT cables scheduled to be implemented this year.(12)

             The TAT-14 transatlantic fiber optic cable system started operating in 2001. As seen in Figure 4, the 15,428 km cable system connects the United States to the United Kingdom, France, The Netherlands, Germany, and Denmark by 10 Gbps Direct Wave Access (DWA) or STM-16, STM-4, and STM-1 interfaces. There are four fiber optic pairs configured for 47 x 10 Gbps DWDM channels of which 10 are utilized for dual, bi-directional SDH rings. TAT-14 has a total design capacity or 3.2 Tbps calculated as: 2 (North & South Routes) x 4 Fiber Pair x 40 10 Gbps channels = 3.2 Tbps. TAT-14 has a total system capacity of 1.87 Tbps calculated as: Southern route: 41 x 10 Gbps channels + 640 Gbps SDH capacity, Northern route: 18 x 10 Gbps channels + 640 Gbps SDH capacity = 1.87 Tbps.(4)

           The Atlantic Crossing 1 (AC-1) is a private non-TAT cable system owned by Global Crossing. According to Figure 5, it links the U.S., the U.K., the Netherlands, and Germany. It was first implemented back in 1999 and is still being used today. The landing points are in Brookhaven Cable Station in New York, USA, Land’s End Cable Station in UK, Westerland Cable Station in Germany, and KPN Telecom cable station in the Netherlands. The cable length is 14,000 km and has a design capacity of 40 Gbps. It’s current lit capacity is 120 Gbps.(5)

           The Hibernia Atlantic communications cable system was built in 2001. It is now currently owned by CVC Acquisition Company. In Figure 6, this cable system connects Canada, the U.S., Ireland, and the U.K. The design capacity was originally 320 Gbps but has upgraded to 10.16 Tbps. The Hibernia Atlantic network includes 24,000 km of fiber assets. The current landing stations are in Herring Cove, Nova Scotia, Canada, Massachusetts, U.S., Dublin, Ireland, and Merseyside, U.K. A new landing point is planned for Northern Ireland later in 2012.(8)

           Emerald Atlantis has planned a 100 Gbps undersea cable system, hopefully being implemented in late 2012. The Emerald Express is going to connect North America to Europe through Iceland as seen in Figure 7. This cable system has been designed to support 100 x 100 Gbps on each of its six fiber pairs. Emerald Express is projected to be eco-friendly; 100% carbon free and renewable energy powered data centers.(6)


Figure 1 - Fiber Optic Cable

http://en.wikipedia.org/wiki/Submarine_communications_cable

Figure 2 - Fiber Optic Protections

http://www.sciencedirect.com.ezproxy.lib.vt.edu:8080/science/article/pii/S1068520099903085

Figure 3 - Submarine Cable System
Submarine Cable System
http://www.sierraexpressmedia.com/archives/16064

Figure 4 - TAT-14

https://www.tat-14.com/tat14

Figure 5 - AC-1

http://en.wikipedia.org/wiki/AC-1_(cable_system) 

Figure 6 - Hibernia Atlantic

http://en.wikipedia.org/wiki/Hibernia_Atlantic

Figure 7 - Emerald Express

http://subseaworldnews.com/2012/03/16/emerald-networks-and-te-subcom-sign-system-supply-contract-for-trans-atlantic-cable-system