For a DWDM system, the wavelength selection and frequency spacing comply with（），recommendation while that of a CWDM system comply with the requirements of （）。
第1题：
DWDM是什么？
第2题：
A. fiber failure between Sites A and d
B. EDFA failure at Site A (clockwise direction)
C. EDFA failure at Site C (clockwise direction)
D. 15216 multiplexer at Site A (counter-clockwise direction)
E. OADM pass-through (West "OUT") failure at site D (clockwise)
F. wavelengths 1 and 3 transmitter failures at Site A (clockwise direction)
第3题：
与DWDM比较，CWDM具有哪些特点？
第4题：
Dense Wavelength Division Multiplexing (DWDM) is an important innovation in optical networks.Which two descriptions best define DWDM?（）
第5题：
中国电信的省内环网通常采用（）和（）系统混合组网方式。
第6题：
A. 0.4 nanometers
B. 0.6 nanometers
C. 0.8 nanometers
D. 1.2 nanometers
E. 1.6 nanometers
第7题：
A. optical technology for transmitting up to 32 channels over multiple fiber strands
B. optical technology for transmitting up to 16 channels over multiple fiber strands
C. a WDM system that is compatible with EDFA technology
D. a technology for transmitting more closely packed optical signals using more sophisticated transceiver designs than CWDM .
第8题：
A.DWDM、SDH、OLT、ONU、PCM
B.DWDM、SDH、PDH、OLT、ONU
C.DWDM、SDH、MSTP、ASON、PDH
D.OLT、ONU、PDH、DDF、VDF
第9题：
铁路传输设备主要包括（）等设备。
第10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?（）