Moreover, this type of wavelength switching, provided by the fibre-intrinsic absorption, turns the grating insensitive to the external low temperature fluctuations.Another important topic in optical switching is the required optical power to switch between adjacent channels according to the ITU-T recommendation G.694.1. Table 1 shows the required optical pump power to perform all-optical switching in the different WDM systems, with the CW 1480-nm pump. Note that, when the grating is written in the doped fibre, the required pump power is more than two times lower than in the case of the FBG written in the undoped fibre. Structures based in Er-doped fibre gratings will be more viable and will achieve a higher dynamic tuning range.One of the possible applications of the device based in the technology presented herein is an OADM with wavelength selectivity, shown in Figure 6. This is a classical optical add-drop multiplexer (OADM), but with switching-enhanced capabilities. CONCLUSIONAn all-optical switch has been proposed and demonstrated. The spectral characteristics of the architecture were presented.The operation of the all-optical switch has been experimentally investigated and its performance evaluated. It was shown that the tuning range can be enhanced by using two pump laser diodes.This all-optical switching technique, apart from finding a direct application in an OADM architecture, can also be integrated in different all-optical networking devices, such as optical cross connects, optical multiplexers and demultiplexers, and other types of wavelength routers.

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The formation and characterization of narrow-band-waveguide reflection filters in Ge-doped silica optical fibers is described. The filters can have complex response profiles and are tunable in frequency by mechanical strain.

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The nonlinear optical coefficients of AlN have been determined as ‖d33‖= (23.2±35%) dQ11 and ‖d31‖ ≲0.04‖d33‖ for the c-plate film and for a fundamental beam at 1.064 μm. The result is discussed with reference to the bond-charge model.