G.652光纤有两个应用窗口，即1310nm和1550nm，前者每公里的典型衰耗值为0.34dB，后者为（）。

DWDM系统是指波长间隔相对较小，波长复用相对密集，各信道共用光纤一个（）窗口，在传输过程中共享光纤放大器的高容量WDM系统。

通信企业营销策划按照策略的内‘容分为战略策划和战术策划。

此题为判断题(对，错)。

以下没有在光纤通信网络中使用的复用技术是()。

A.空分复用

B.波分复用

C.码分复用

D.时分复用

With the explosive popularity of mobile devices, we have witnessed a steady increase in demand for mobile date service. In addition mobile users also expect to connect to the Internet for communicate and access to services through the best suitable connection, anywhere and at anytime. Although the seamless roaming capability is well supported in conventional. Cellular communication networks, roaming and interworking technologies are still immature in heterogenous wireless networks. Seamless roaming over heterogenous wireless networks will be an ongoing and improved process, due to the requirements from both end users and network administrators. From the wireless access networks belonging to different administrative domains, mobile users cannot always identify at every instance which network is the best one to access for their service. It is highly demanded to establish a network architecture which can facilitate mobile terminals to access the appropriate network in a cost-effective way. If a mobile user wants to move from one network to another with continuous service, the terminals have to cope with network change to maintain service seamlessly. Quality of service is a major issue that the end users should be provided with the satisfying service, while the network workload and cost should not too much increased. In addition, since end users are provided with numerous service ranging from Voice-over-IP to Video-on-Demand services, it is expected that users can experience the same quality for all the different service. Therefore, the network architecture need to be designed in such a way that the quality mechanism is incorporated so that users are served according to their individual QoS requirements. Based on the paragraph above, at present, seamless roaming over heterogenous wireless network is () in conventional cellular communication networks, Because of (), mobile users cannot always identify at every instance which network is the best one to access for their services. To satisfy the users QoS requirements, the network architecture design should include () A.better than

B.maturer than

C.as good as

D.not as good as

49.A.the different network administrative domains

B.the same network administrative domains and mobile users

C.mobile users

D.the same network administrative domains

50.A.Voice -over -IP

B.the quality mechanism

C.workload

D.Video-on-Demand

请帮忙给出每个问题的正确答案和分析，谢谢！

在同等增益条件下，天线垂直波瓣3dB越窄，覆盖死区越少。()