单项选择题
A. The glass core is doped with an Erbium in periodic segments of the fiber.
B. Layers of high index ？and low index ？material are deposited on a glass substrate.
C. Thin layers of silica glass are placed onto wafers to produce a prism-like effect.
D. Fiber is etched with an ultraviolet laser that is precisely spaced for specific wavelength filtering.
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 （）.
单项选择题 In the OSNR model for EDFA amplifiers， SNR OUT = 1/（1/SNR IN + FhvB/P IN ）， what does SNR IN represent？（）
单项选择题 The dispersion of a non-zero dispersion shifted fiber is 6 ps/nm*km at 1550 nm and 10 ps/nm*km at 1610 nm. What is the minimum dispersion compensation required if an L-Band DWDM signal travels through 200 km of fiber and has a dispersion tolerance of 1800 ps/nm？（）