Evaluations for transponder utilizations of two active–standby banks in CD-ROADM optical networks with traffic grooming

Reconfigurable optical add/drop multiplexers (ROADMs) are being widely deployed by network carriers in transparent optical networks to increase dynamicity and flexibility. Next-generation ROADMs request colorless, directionless, and contentionless (CDC) features. We evaluate static lightpath blocking performance with different transponder (TP) bank sizes (i.e., number of TP used), to optimize the TP configuration in colorless and directionless ROADMs (CD-ROADMs), while maintaining similar blocking performance as that for a pure contentionless ROADM. In this paper, we introduce an integer linear programming model considering intra-node resource limitations. To achieve scalability, we develop an efficient heuristic algorithm which also takes into account the ROADM add/drop structure. Simulation results show that the two active–standby banks in the CD-ROADM node are able to provide the contentionless feature. Furthermore, the number of TPs in the standby bank can be reduced to 37.5 % of that in the active bank, where TP number is same as the number of wavelengths in each fiber link, in order to simplify CD-ROADM configurations and to reduce its implementation cost. The causes of traffic blocking in the CD-ROADM optical networks are also analyzed.