nalty (EOP). If the receiver samples the signal in the instants tk indicating with s(t,b) the signal immediately before sampling with its dependence on time and on the transmitted bit b, the EOP is defined as follows: EOP=10log10Si(ti,k,1)-10log10s(tk,1)+10log10s(tk,0) (6.5) where siltiki 1) is the ideal received signal sampled in the ideal instant ti,kr while the ideal received signal for a zero is considered to be zero. In the presence of random phenomena, like thermal or quantum noise, the EOP is a random variable, and often its average is considered to eliminate the noise and to identify the effect of distortions. In case more distortion effects are present, the EOP can also be expressed in a first approximation as the sum of the EOP relative to each single effect. The procedure to demonstrate it is similar to that used for the SN and the carrier; it brings to write, in the case of two distortion causes with characteristic parameters A and B, respectively, EOP(dB)=EOP(A)(dB)+EOP(B)(dB (6.6) where EOP(A) and EOP(B) indicate the EOP in the presence of only one of the distorting phenomena. 6.2.2 Ideal IM-DD Transmission In this very preliminary analysis, we will assume the following simplifying assumptions: The transmitted message is binary. The system is point-to-point. Only one signal propagates along the transmission line. Information is coded in the signal amplitude. The fiber transmission is ideal, that is, without dispersion and nonlinear effects. All transmitter components and all receiver components are ideal; thus, only noise affects the receiver detection. No optical amplifier is used. In this condition, the baseband transmitted signal can be written as (6.7) where m(t) is the pulse that has to shape the transmitted field T is the period of the transmission: 1 bit transmission will take T seconds The inverse of this period R=1/T = is called bit rate. Telecommunication Networks Two possible modulation types exist depending on the shape of m(t): if it is constant in the bit time and zero (or again consta