Telecom networks generally have been deployed in the C-band optical spectrum, where fiber attenuation is lowest. However, as network traffic continues to grow rapidly, operators are quickly running out of C-band spectrum to increase capacity. Expanding network deployment to the L-band is a cost-effective approach to enable operators to reduce OPEX for dark fiber/IRU leases. This white paper presents a model for the analysis of C/L-band business cases, with the objective of enabling network operators whose Outside Plant fiber infrastructure is based on leased dark fiber/IRU to determine the optimal architecture for achieving cost efficiency and network scalability.