多项选择题 Click the Exhibit button. When designing a DWDM system with multiple amplified spans, a pre-amp is needed at Site B to （）. (Choose three.)

单项选择题 How is a Thin Film filter fabricated?（）

单项选择题 For lasers with tightly controlled wavelengths, approximately how far apart are the centers of adjacent wavelengths when 100 GHz spacing is used in a DWDM system?（）