.55 um) that is a very good bandwidth to operate as multi-wavelength TODC in DWDM systems. The group delay is shown in Figure 9.5 versus the wavelength deviation for different values of a. The group delay behavior is, in this ideal case, linear with the wavelength with a very good approximation, thus confirming the good performance of this architecture in conjunction with fiber Brag gratings. Naturally, in practical implementations, several nonidealities affect the behavior of the TODC, like reflectivity of the gratings, ripple in the phase characteristics of the dispersion elements, losses of the whole device, and SO on. A detailed analysis of such impairments besides a practical implementation of a compensator and a transmission experiment are presented in [2]. Moreover in [2] it is also shown that a compensator with the architecture of Figure 9.3 can also be used as a single channel compensator coupling the signal directly in the elec- trical domain. In this case, the compensator is an alternative to electronic compensation. Several other architectures have been proposed for the TODC, having different characteristics. A class of compact TODC are based on the use of Array Waveguides (AWGs) [3,4] since these devices provide contemporary demultiplexing and different dispersion contribution channel per channel. Moreover, if suitably designed, the same AWG can be used both for multiplexing and for demultiplexing the DWDM comb increasing the dispersion contribu- tion and gaining in compactness. An example of AWG architecture is presented in [3] and is reported in Figure 9.6. The component working is quite simple. The incoming optical field is decomposed by the AWG, which divides its spectrum slices, its spectral phase around the center frequency is adjusted by the lens located near the spectral plane, reflected by the mirror, and recom- bined in the AWG to regenerate the field. Depending on the AWG design, this TODC can be used either to compensate interchannel dispersion due to the dispersion slope in par- ticularl