Now that you have learned about fiber-optic hardware, standards, and system design, it’s time to look at how fiber-optic systems are used. Changing technology and regulations are eroding traditional divisions, but it is still useful to separate telecommunications into a few sectors. The largest in scale is the global telecommunications network, the backbone of international telecommunications, including long-distance transmission under the oceans and on land. Other sectors are regional or metro networks and distribution networks for voice, video, and computer data services. You learned a little about these ideas in Chapter 3; now it’s time to take a closer look.
In this chapter, I will describe the long-distance fiber-optic transmission systems that carry data, voice, video, and other signals around the world. They include intercontinental submarine cables as well as national and international systems on land. They are the world’s biggest telecommunications “pipelines,” and they are designed to maximize both transmission speed and distance. Fiber-optic technology has dominated these systems for over a decade, first with single-channel single-mode transmission, and now with high-speed DWDM systems.
These long-distance networks feed into regional or metro networks, which in turn
connect switching offices and distribution networks, which deliver services to individual homes and offices. Later chapters will look at those networks.
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