This book, Modular optical systems for nonlinear data processing and manipulation, presents the PhD thesis under the same name, submitted in 2003. The work combines knowledge in image processing, switching in communication networks and knowledge in modern optics, especially in the field of Diffractive Optical Elements (D.O.E). The main topics covered in this book are: Multi stage binary phase-only image processing, Optical multi stage interconnection network (MIN) optimization, Optical implementation of non-linear operators such as the Volterra operators, and Optical implementation of Fuzzy logic controllers. This book covers a variety of fields relevant for electrical engineers interested in exploring the wonderful world of optics from the system designer point of view and offer a window to some of the most fascinating applications of optical systems.