In other words, the unipolar laser signal, (), is cross correlated with a reference, ′(), which is a bipolar version of itself. While this subtle point is often mentioned in works dealing with pseudorandom coding using incoherent optical signals, rarely do implications arise because of it. However, we shall later see that this transformation can have significant impact on the shape of the cross correlation for this application depending on the type of code used.We describe the impulse response of the medium as