What are optical networks？

Question

What are optical networks？Why are they becoming important？

Answer 1

http://www.cht.com.tw/CompanyCat.php?CatID=350SONET (Synchronous Optical Network) 是由 Bellcore 在 1985 年所制定，以 STM (同步傳輸模式) 架構於光纖媒體上的一種網路設備，這個網路建立於 ANSI T1.102、T1.105、T1.106、T1X1.5 等標準。SONET 可以提供超過數百 MB 的頻寬，特別適用來作為電信系統、網際網路的骨幹(backbone)，目前國內 NII 的主要目標之一，便是以 SONET 作為台灣地區Internet 的主幹線。很抱歉！回答內容限 2000 個字之內http://en.wikipedia.org/wiki/Synchronous_optical_networkingThe Synchronous optical network, commonly known as SONET, is a standard for communicating digital information using lasers or light emitting diodes (LEDs) over optical fiber as defined by GR-253-CORE from Telcordia. It was developed to replace the PDH system for transporting large amounts of telephone and data traffic and to allow for interoperability between equipment from different vendors. The more recent Synchronous Digital Hierarchy (SDH) standard developed by ITU (G.707 and its extension G.708) is built on experience in the development of SONET. Both SDH and SONET are widely used today; SONET in the U.S. and Canada, SDH in the rest of the world. SDH is growing in popularity and is currently the main concern with SONET now being considered as the variation.SONET differs from PDH in that the exact rates that are used to transport the data are tightly synchronized across the entire network, made possible by atomic clocks. This Telecom Synchronization system allows entire inter-country networks to operate synchronously, greatly reducing the amount of buffering required between each element in the network.Both SONET and SDH can be used to encapsulate earlier digital transmission standards, such as the PDH standard, or used directly to support either ATM or so-called Packet over SONET networking. As such, it is inaccurate to think of SONET as a communications protocol in and of itself, but rather as a generic and all-purpose transport container for moving both voice and data.