s in conjunction with suitable compensation of the modal dispersion at the receiver. The core of multimode fibers is much bigger with respect to the core of single-mode fibers and all the alignment processes are easier. Moreover, provided that a suitable equalization is incorporated in the receiver, lower quality sources can be used with respect to the trans- mission on a single-mode fiber. The critical aspect related to the difficulties in incorporating a glass fiber into a stan- dard PCB remains. In order to relieve this difficulty glass has to be substituted by a more resistant material. Here comes into play plastic optical fibers that seem a promising solution for this application, even if their transmission performances are not SO good as glass fibers. Research is also quite intense on the possibility to directly integrate on the backplane PCB dielectric optical waveguide, using either a deposited crystal material or a suitable polymer. As far as connectors are concerned, optical connectors do not yet have the performances of electronics ones, but great processes have been done [47] and there is a diffused con- sensus that, if the present day's trend will be confirmed, there will be a moment in which optical backplane will become preferable to electrical ones, and it is not SO far [48]. 7.5.1.3 Optical Backplanes Based on Monolithic Optical Integration Besides the more traditional idea of the optical backplane sketched in the previous section, few among the larger companies of semiconductors in the world are carrying out a con- siderable effort in a different direction. The idea behind these projects is that the need of structuring a communication network among cards of single equipment at very high speed is not limited to telecommunications, but is common with computer industry, manufacturing automatic equipment, and a set of other applications. This could drive large volumes of market that justify the application of monolithic integration technologies allowing low costs to be reached. If this forecast is t