We extend various bit-level and word-level expressions for representation of switching functions, such as SOP, Reed-Muller expressions, arithmetic, and Walsh expressions, to functions used in Fibonacci interconnection topologies. The corresponding Fibonacci decision diagrams (FibDD) are used as graphic representations of these expressions. At the same time, FibDD are used as a data structure to efficiently calculate coefficients in the introduced expressions, and to perform design of related networks. In this way, we provide a base to extend the application of powerful CAD design tools for switching functions to functions in Fibonacci interconnection topologies.