Universal fiber is an optical fiber that supports both multimode and single-mode transmission. It is a multimode fiber with a mode field diameter of the fundamental mode roughly matching that of a standard single-mode fiber. In today's short-distance communications, both multimode fiber and single-mode fiber are used. Universal fiber can accommodate the needs of single-mode and multimode transmission so that end users can take advantage of the cost and performance benefits of each transmission type. In this paper, we present the design and properties of universal fiber, as well as its transmission performance for 100G systems. We also explore several application scenarios where the fiber can be utilized. In particular, we illustrate how the fiber can be used in 5G wireless fronthaul applications to meet the current needs while providing a path for future upgrades. Testing results and discussions of practical issues are also presented.