Conclusion
In all cases, the main application which emerged from the research efforts deals with optical gratings because they were in the field for which the needs in miniaturization were the most urgent. First of all, the main concern was to reduce the size of the routers for DWDM[1] applications by a scale factor similar to that allowing to pass from the size of a refrigerator to the size of a mailbox. It was an important need, not only because such DWDM nodes should be integrated in urban distribution central spots but also because an exponential growth in the demand in terms of production capacity was expected.