| 单词 | core |
| 释义 | core 1. The central or essential part of a Wide Area Network (WAN) or Metropolitan Area Network (MAN) is commonly known as the core, or backbone. The network core comprises very high capacity elements and subsystems such as transmission systems, multiplexers, switches, and routers. See also MAN and WAN. 2. The central and primary light-conducting portion of a glass optical fiber (GOF). The core is the inner portion of the fiber into which the optical signal is injected by either a light-emitting diode (LED) or one of many types of laser diodes. A single-mode fiber (SMF) used in a high speed, long haul fiber optic transmission system (FOTS) has a very narrow inner core, 5–10 microns in diameter. A multimode fiber (MMF) used in a relatively low speed, short haul system has a relatively broad core that typically is either 50 microns or 62.5 microns in diameter. See also cladding, GOF, laser diode, LED, MMF, and SMF. 74570c03.qxd 9/11/07 12:19 PM Page 114 |
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