nterested reader to consult [12,13] and Section 9.2.3.2. 6.2.4 Performance of Non-Regenerated NRZ Systems In order to analyze the effect of all the transmission impairments that are included into Equations 6.36 and 6.37, let us concentrate on the optimum receiver structure: that with the adaptive threshold. When it will be necessary to evaluate numerical results in this section and in the fol- lowing, we will use a set of representative parameters reported in Table 6.1, but for fibers' parameters, that are reported in the Table 4.1 of Chapter 4 for the SSMF and in Table 4.2 of the same chapter for NZ + and NZ- depending on the fiber type. Telecommunication Networks TABLE 6.1 Reference System Parameters for the Performance Evaluation Carried Out in the First Part of the Chapter Transmitter Perfectly squared pulse Bit rate 10 Gbit/s (40 Gbit in some examples) Dynamic range 20 dB Transmitter loss (up to the booster input) Laser alternatives Standard DFB Nontunable 13-20 dBm emitted power Multisection DBR Tunable 16dBm emitted power (with SOA) External cavity Tunable 13-16 dBm emitted power Receiver Responsivity Photodiode thermal noise current amplitude density 2 pA/ 4RB J Fa/Ra Dark current power (PIN) Electrical bandwidth 10GHz INGaAsP APD ionization ratio (ri) Spectral densities of the APD dark current 2.5 X 10-23 A2/Hz components (Sbd and Ssa) Receiver loss, from the preamplifier output to the APD The first impairment to analyze is chromatic dispersion since in standard single-mode fiber (SSMF) it generates a rapid widening of the transmitted pulses. To analyze system performances we will require a BER of 10-12 and in agreement with ITU-T recommendations we will evaluate the dispersion limit reach for each system as the distance at which the dispersion induced penalty is 2 dB. The performance of an NRZ system with no SPM and no PMD, are reported in Figure 6.7. -28,5 -26,4 -24,4 -22,3 0,0001 L 1km 1E 07 1E 10 BER = 10-12 1E 13 1E 16 -25.1 Received power (dBm) FIGURE 6.7 Performance of an NRZ system with no SPM an