Virtualization has yielded significant benefits to compute, storage, and networking domains. In this work, we seek to virtualize unused optical fiber assets known as dark fiber. To this end, we propose and build a system called vFiber to spin up optical fibers between the endpoints (e.g., switches) of an enterprise network. We evaluate the efficacy of vFiber using a lab-based testbed composed of Cisco 3560-E switches, Coarse-Wavelength Division Multiplexers (CWDMs) and an in-house benchmarking capability. Our experiments show that vFiber can scale the network capacity from 942 Mbps to 3,763 Mbps in 9 seconds and that vFiber is resilient to multiple failures.