hi umar syed,
more losses are associated with transmission because the length has increased hand to compensate those losses , the requirement of the parameter (say power) increases linearly and then suddenly the requirement drops..
i now think that nagative penalty(db) means that we should decrease power so as to reduce the effect of eye closure
i my self thinks now that penalty for eye opening can be both positive and nagative
case1:positive penalty: in this situation we require to compenate the losses of any parameter in design such as length.
case2:nagative penalty: there may be case where excess of power may create nonlinearities and other thermal noise at reciver end,
hence we should reduce the power, threfoe the penality is nagative.>>>>>>>>>>>>.
hope this will hrelp abit. and for futher details go for my same post
with reagards