Return loss of Optical Passive Component

The reflection of light occur in passive component when the advancing light meet any cut sections or the discontinuous place of refracting rate, air gap, misalignment, …etc.

The reflecting question can cause two-piece, the first is the noise of reflection can cause S/N ratio to be worse. The second is the reflecting energy will cause laser source (maybe optical transmitor) to be unstable.

So, we defined a parameter, Return loss:
Return loss = -10log(Pr/Pin).As we know, the greater its value is, the more difficult to produce it is.