 there is no possibility to reply with integrated optics the success of microelectronics, it is evident that there are specific situations in which monolithic integration is useful. The most important is the case of lasers with an integrated modulator (either EA or Mach-Zehnder) and in the case of an output semiconductor optical amplifier. Devices of this kind are regularly used in telecommunication systems and have the advantage of putting into a single package three elements, sparing on package and con- nections and reducing interface loss. This solution is particularly appreciated when a tunable multisection laser is used in conjunction with a Mach-Zehnder modulator. 5.6 Optical Switches Under the category of optical switches all the optical components can be collected that deflect the light either in free space or in guided propagation from one direction to the other. In telecommunication, optical switches are used almost only in conjunction with fiber propagation, but for the free space application, which is sometimes used as temporary con- nection either between nearby units or between parts of a broken cable [42]. Switches used in fiber-optic systems can be classified into two categories: semi-static switches and routing switches. Semi-static switches are those subsystems that are installed instead of a patch panel to gain flexibility: from a functional point of view they are not routing elements in the network, instead they are part of the cable infrastructure like patch panels, ducts access points, and SO on. These switches are generally micromechanical switches and change status quite rarely, sometimes never in their life. Thus, it is very important that they maintain the characteristics of attenuation and polar- ization insensitiveness for a long time and that they are able to work after a long time of inactivity. On the other hand, no important requirements on speed, power consumption, or dimen- sion are generally imposed on these components, but for the fact that without power sup- ply they cannot ch