In this paper, we present three switch architectures for WDM (Wavelength Division Multiplexing) Benes network that are based on wavelength exchange optical crossbar (WOC). A WOC is capable of performing a single-step space-switching wavelength-conversion between two wavelengths. A WOC can be implemented by the simultaneous power exchange between two optical signals. Unlike existing designs, the proposed architectures do not require separate stages of wavelength converters. This leads to a switch design that has a smaller total number of components as well as a smaller number of components in the signal path. Moreover, wavelength conversion is performed between two predefined and fixed wavelengths. This avoids the need for expensive full-range wavelength converters used in most of the existing designs. Systematic methods to realize switch architectures with an arbitrary number of wavelengths and fibers are given. The three architectures are evaluated and compared to existing architectures on the basis of hardware cost.