This book is about designing high-density nonblocking photonic switches. Crosstalk, signal attenuation, and nonblocking type are considered the most critical issues that limit the switch density in photonic switches. The book provides a theoretical study to develop high-density photonic switch architectures with reduced crosstalk and attenuation and improved nonblocking performance. Four photonic switching networks have been proposed based on directional couplers. Ideas from the theory of circuit switching have been considered and space dilation techniques have been adopted using new approaches. The properties of the proposed networks have been examined and formulated. Comparison with other well-known designs has also been presented and analyzed. If you are interested in performance analysis and enhancement of telecommunication switching networks, this book will definitely suit you.