 most important integrated component for the processing of the optical signal is the so-called photonics integrated circuit (PIC). This highly integrated component is devised to drastically decrease the capital expenditure (CAPEX) that is due to the repetition of costly high-speed optical interfaces every time the signal has to be converted from optical to electrical. The functional scheme of a transceiver realized with a transmitting and a receiving PIC is represented in Figure 10.1. In the transmitting PIC, a bar integrating a certain num- ber of lasers is coupled with a multiplexer/demultiplexer (generally an array waveguide [AWG]) that launches the multiplexed channels into the output fiber. The scheme of a receiving PIC is identical, with a demultiplexer, a bar of photodiodes, and with the WDM signal incoming from the input fiber. Both the coarse wavelength division multiplexing (CWDM) and DWDM PIC can be realized, and similarly to CWDM small form factor pluggable (SFP), it seems possible to implement CWDMPIC without thermal stabilization. Two possible technologies exist to realize PICs: a complete monolithic integration on an InP substrate and hybrid integration. In this last case, the AWG is realized in another integrated optical technology (e.g., high index contrast Si SiO obtained with a high doping of the glass with Germanium) SO as to interface the fiber on one side and the laser bar on the other. Both the technologies have advantages and disadvantages: monolithic technology has to face a relatively big area circuit compared with the small wafers used in InP foundries, SO uniformity is necessary. Hybrid technology realizes the part of the component with the wider area using Si wafers, at least in. large versus the in. of InP wafers, SO attenuating uniformity problems, but introduces the difficult operation to be performed chip by chip by interfacing two different chips in the package. In both the cases, however, what is expected is a drastic price reduction of interfaces integrated into a PIC with resp