 Extended 1+1 OChP ETSI standard cabinet Gbit/s Gbit/s 10 Gbit/s (with C band 1:N transponder 2200 mm 80 @ 40 Gbit/s channel spacing protection (height) X 600 mm Gbit/s 100 GHz) (width) X 300 mm 1000 km @ 40 (depth) Gbit/s Long haul 2.5 or 10 or 320 @ 10 Gbit/s 25 GHz 4000 km @ Extended Electrical Both ANSI and ETSI 40 Gbit/s 10 Gbit/s (with C band dispersion standard racks Gbit/s 100GHz compensation spacing) (EDC) Regional 1000 km @ 10 Gbit/s Regional conf. Transmission Systems Architectures and Performances Even if hybrid approach is used, co-propagating Raman pumps, counter-propagating Raman pumps, or both can be used. In general, the design is more complicated with respect to what is described for long- haul systems. We will introduce the main points of the design of such systems by analyzing one of the most common architectures. This is the architecture based on hybrid EDFA-Raman amplifiers, where the Raman pumps are located in the EDFAs locations and generate signal gain by counter-propaga- tion along the DCF. We will assume that fiber dispersion is compensated by in-line DCF adopting under compensation to control XPM and SPM. Due to the good Raman gain of the DCF, a single-stage EDFA is used, and the Raman pumps are propagated through the DCF to provide distributed amplification and blocked at the end of the DCF since propagating them through the SSMF used for transmission generates noise and creates limited gain due to the pumps attenuation experimented dur- ing the pass through the DCF. The block scheme of the line site is reported in Figure 6.28. Since the system will use extended C band, two Raman pumps are enough to achieve a flatness of the Raman gain on the order of 0.5 dB; overall gain flatness is achieved via a gain flatness filter at the output of the EDFA. The advantages that are expected from the hybrid amplifier configuration are as follows: Once fixed, the received power that assures the required receiver sensitivity, the Raman gain allows the optical power at the EDFA output to be reduced SO