在光纤通信标准中，OC-3的数据速率是()。
- A.51Mb／s
- B.155Mb／s
- C.622Mb／s
- D.2488Mb／s
正确答案及解析
正确答案
解析
本题考查常用数字传输系统的基础知识。1985年，Bellcore提出同步光纤网传输标准SONET(Synchronous OptionNetwork)。1989年，CCITT参照SONET制定了同步数字系列标准SDH(Synchronous Digital Hierarchy)，两者有细微差别，如表8-4所示。
SONET／SDH是一种通用的传输体制，不仅适于光纤，也适于微波和卫星传输，是宽带综合业务数字网(B-ISDN)的基础。SONET／SDH采用TDM技术，是对原来应用于骨干网的准同步数字系列(Pseudo-synchronous Digital Hierarchy，PDH)的改进。SONET用于北美地区和日本，SDH用于中国和欧洲地区。
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