WDM系统中,若发端放大板前的可调衰减器衰减量发生变化,哪个系统参数不会会受影响?()
A、信噪比
B、增益平坦度
C、总色散
D、光纤非线性效应
参考答案:C
We’re talking about the piano and the pianist _____ were in the concert we attended yesterday.
A.which
B.whom
C.who
D.that
电力机车构架的主要承载粱是().
A.横梁
B.端粱
C.侧梁
D.枕梁