In this paper, we propose a new WDM photonic switch architecture, called Wavelength Exchange Cross-Connect (WEX). The proposed architecture is based on a new paradigm single-step space switching and wavelength conversion. This paradigm is realized using Wavelength Exchange Optical Cross-bar (WOC) that can be implemented by simultaneous exchange between two optical signals. The WEX architecture eliminates the need for separate wavelength conversion stages that are used in most existing switch architectures. This leads to a switch design with a smaller number of components and simpler control. A systematic method for developing instances of the switch architectures with an arbitrary number of wavelengths and fibers is presented.