单选题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 amplifierB
the signal to noise of the previous amplifier or sourceC
the signal to noise introduced
题目
单选题
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
