and after the preamplifier have to be accounted for. These are due essentially to the multiplexer and the demultiplexer, to connectors and patchcords connecting the different cards, and to taps used to monitor the optical signal. us indicate with am the loss of the multiplexer and the demultiplexer and the extra losses at the transmitter and at the receiver respectively, with PL the optical power exiting from a transmitter after modulation and with Ps PIN the input saturation power of the receiver. Realistic values for these parameters can be found in Chapter 4 and are summarized in Table 6.2. The power budget equations for the system are as follows: The equation assuring that the booster amplifier is saturated SO to inject into the line the correct power 10 log10(nc)+PL(dB)-am(dB)-axt(dB)>Ps,booster(dB) (6.74) Telecommunication Networks where n is the number of channels PL is the power emitted by the transmitting laser am is the multiplexer loss is the transmitter chain loss (containing the modulator, the passive optics, and SO on) Finally Ps,booster is the booster input saturation power. The equation that determines the maximum span that can be covered by the in- line amplifiers (assuming that the output power of the booster is the same of that of in-line amplifiers) (6.75) a(dB/km) where a is the fiber loss in dB/km is the amplifier insertion loss Ps and Pout are the line amplifier input and output saturated power The span length is indicated with Ls. The equation that assures that the received power is sufficient to neglect the ther- mal noise of the detector but does not saturate the receiver (6.76) where SRec is the receiver sensitivity pout preamp is the saturated output power of the preamplifier is the demultiplexer loss ARC is the whole receiving chain loss In the case of the parameters reported in Table 6.2 Equation 6.74 is fulfilled with a chan- nel number as high as 256 and as low as 16; thus, the transmitter power budget is almost automatically fulfilled. Equation 6.76 is also satisfied, while the ma