Rapid network growth due largely to video traffic and other bandwidth-hungry services—such as IoT and cloud-based storage—is leading network operators to seek and deploy network architectures that will best serve their cost and scalability needs as their network capacity increases over time. So, which is more cost-efficient: investing in a one-time CAPEX to upgrade the network to C+L-band, or leasing a new pair of dark fibers and paying OPEX for a dark-fiber lease/IRU in perpetuity? This paper addresses this important business question and recommends a solution for network operators.