If the dispersion of a given fiber is 17ps/nm*km at 1550 nm and zero at 1310 nm， then what is the accumulated dispersion of an ITU wavelength after it travels 200 km？ （）

单项选择题HowisaThinFilmfilterfabricated？（）

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 （）.

A. offset the OADM loss at site B
B. overcome the high multiplexer loss at site A
C. amplify signal levels after the high loss through Fiber Span 1
D. adjust add channels at site B to be at the same level as the passthrough channels
E. ensure that the per channel power is higher than the minimum needed for the post-amp at Site B

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？（）

A. the signal to noise of the current optical amplifier
B. the signal to noise of the previous amplifier or source
C. the signal to noise introduced by the optical multiplexer
D. the accumulated noise to signal ratio of the optical channel

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？（）

A. none
B. -600 ps/nm
C. -200 ps/nm
D. +200 ps/nm
E. +600 ps/nm

单项选择题Forlaserswithtightlycontrolledwavelengths，approximatelyhowfarapartarethecentersofadjacentwavelengthswhen100GHzspacingisusedinaDWDMsystem？（）

A. 0.4 nanometers
B. 0.6 nanometers
C. 0.8 nanometers
D. 1.2 nanometers
E. 1.6 nanometers