**7. Conclusion**

In this Chapter we considered different approaches to development of multi-channel adaptive measurement systems based on multiplexing of dynamic holograms in a photorefractive crystal. We show that such systems can provide (i) high sensitivity to detection of ultra-small physical quantities (close to the classical homodyne detection limit), (ii) cross-talk free performance, and (iii) adaptive properties which cancel uncontrollable environmental influence on the system. For development of such systems different approaches to dynamic holograms multiplexing, including spatial, angular, spectral and their combinations, can be effectively used. Moreover, dynamic gratings recorded in a photorefractive crystal can also be used for development of such elements of multi-channel systems as spectral tunable filters which can provide effective demultiplexing of signals with different wavelengths.
