光纤通信简介专业英语要点.pdf

Optical Fiber Communication -introduction Foreword The use of light to send messages is not new .Fires were used for signaling in biblical times, smoke signals have been used for thousands of years and flashing lights have been used to communicate between warships at sea since the days of Lord Nelson. The idea of using glass fiber to carry an optical communication signal originated with Alexander Graham Bell. However this idea had to wait some 80 years for better glasses and low-cost electronics for it to become useful in practical situations. The predominant use of optical technology is for transmission of data at high speed. Optical fibers replace electric wire in communications systems and nothing much else changes. Perhaps this is not quite fair. The very speed and quality of optical communications systems has itself predicated the development of a new type of electronic communications itself designed to be run on optical connections. ATM (Asynchronous Transfer Mode) and SDH (Synchronous Digital Hierarchy) technologies are good examples of the new type of systems. It is important to realize that optical communications is not like electronic communications. While it seems that light travels in a fiber much like electricity does in a wire this is very misleading. Light is an electromagnetic wave and optical fiber is a waveguide. Everything to do with transport of the signal even to simple things like coupling (joining) two fibers into one is very different from what happens in the electronic world. The two fields (electronics and optics) while closely related employ different principles in different ways. Some people look ahead to “true ”optical networks. These will be networks where routing is done optically from one end-user to another without the signal ever becoming electronic. Indee