The article describes the philosophy of component approach to system design, illustrated on the optical transmission network example. The approach is based on the object oriented paradigms of Cosmos and Nyx tools. Cosmos serves as the support for system and component development, behavior description, and simulation and analytic calculation development. Nyx in turn enables description of optimization procedures using general heuristic search techniques. The combination of these two development environments and their component approach enables reusability and shortening of the new application development time.