In order to maintain the reach of a typical 100G WAN transport system(~1500 km)，several system improvements have to be made to recover the lost（1）,including the use of low-loss low-nonlinearity（2），Raman amplification,and stronger error correction. (1) A.noise B.SNR C.speed D. eeor (2) A.optical fiber B.traffic C.internet D.signaling
