The usual recommendation is to use single fiber for cost-effective, space-saving deployments and dual fiber when capacity and performance are the priority. But there are no hard and fast rules. Architect's Note: The choice between Single-Mode and Multi-Mode isn't just about speed—it's about the physics of light propagation and the total cost of ownership (TCO) including transceivers. Although they can do the same job in some instances, the different construction methods make each of them better suited to certain tasks and budgets. How Far Signals Need to Travel As we mentioned, knowing how far your data signals need to travel will help you choose between singlemode or multimode fiber.