generation SDH/ SONET, but for the fact that the necessity to maintain legacy compatibility is not pres- ent in this case. The huge difference is in the idea implementation, based on the integration between optics and electronics on the same integrated circuit platform, SO as to drastically reduce the cost of electronic elaboration. At the state of the art, silicon photonics is not ready for this task. The major players in the field of silicon photonics are engaged in research for other kinds of applications, and in any case, silicon phonics components do not have yet the required quality to be applied in long-haul (LH) transmission. Telecommunication Networks Besides these "optical problems," the integration of silicon high-performance compo- nents on the same chips of optical components is for sure not given, requiring substantial evolution of the fabrication processes. For the above reasons, integration has been carried out using InP-based platform. 10.2.1 Optoelectronic Integration: ODN Enabling Technology In order to overcome the cost reasons that pushed the telecommunication community to try to eliminate electronics from the transmission systems, the cost of opto-electronics integrated circuits has to decrease. A progressive integration of more functionalities and an increase of the volume will help recover and overcome the cost gap with optical trans- parent components. With regard to functionalities, a lot of different functionalities have been integrated into a single chip built on InP platform. Tunable sources are a reality both in the form of laser arrays and in the form of multisec- tion distributed Bragg reflectors (DBRs) (see Chapter 5). In the first case, the chip contain- ing the lasers also integrates a tunable combiner, generally, a microelectrical mechanical machine (MEM) switch. In the second case, a modulator and a semiconductor optical amplifier (SOA) are frequently integrated in the laser chip SO as to demonstrate the ability to put several different optical components on the same chip. The