Wavelength allocation in regional access network with optical add-drop multiplexers

Optical add-drop multiplexers (OADMs) may cost-effectively provide regional nodes with large bandwidths. But, each dropped or added wavelength requires a costly TDM terminal. We discuss ways to decrease the number of TDM terminals in regional access networks (RANs) with OADMs, while ensuring high network utilization and sufficiently low probability of blocking new connection requests. We propose two wavelength assignment schemes that provide full-connectivity in RANs with fixed-tuned OADMs: (1) wavelengths are assigned to nodes according to the Hadamard code, and (2) bands of contiguous wavelengths are assigned to nodes. Simulation results show that on average, the Hadamard wavelength assignment schemes approach the performance of RANs with OADMs that add-drop all wavelengths, while saving 50% of the TDM terminals. The saving of TDM terminals by using wavelength tunable OADMs vary in different cases. Tunable OADMs are advantageous for lower traffic granularity and more interactions of a RAN with the outside network.