光纤通信技术,英文版,chapter6.1,中国计量学院.ppt

8.2 connectors Major characteristics Insertion loss (插入损耗） Return loss (reflectance or backreflection)（回波损耗） Repeatability(Durability)（重复性） PM connectors （偏振保持连接器） Angled physical contact (APC) Problem Why is the polishing angle for APC connectors 8 Repeatability Typically, this increase is 0.2dB for 500 matings. A clean ferrule endface, immune to scratches and other microdamage, can hold up during many matings. Just remember, it is the installer’s responsibility to keep a connector clean form dirt and dust. 8.4 design of local-area-network installation Link consideration—power budget and rise-time budget(bandwidth) 链路考虑-功率预算和上升时间预算（带宽） Power budget 功率预算 The question is this: Does the light signal arriving at the destination point of a link have enough power to be detected by the receiver? Power budget consideration allows us to calculate power at the receiving end and know the loss allocations along the link. The piece of advice for a designer: always keep reasonable power margins because your network will grow; therefore, you will need to connect new users and include new components, steps that are accompanied by power loss. bandwidth The main advantage of an optical fiber over copper wire and other transmission media is its tremendous information-carrying capacity, or bandwidth. To make sure that the fiber bandwidth guarentees the required transmission speed, youcan calculate link bandwidth. A local data link is to be installed having the following characteristics: maximum bit rate, 16Mbit/s; installation length, 2000m; operating wavelength, 850nm; rise time of the lightwave equipment, 4ns, and LED spectral w