Optimal placement of reconfigurable optical add/drop multiplexers with packing, blocking, and signal loss

With technological and manufacturing advances, and increased economies of scale, today the use of Reconfigurable Optical Add/Drop Multiplexers (ROADMs) has become economical. A ROADM allows individual or multiple wavelengths to be added and/or dropped from a transport fiber without the need to convert the signals to electrical and back again to optical. This feature makes a fiber optic network more flexible, i.e., the network can be remotely configured/reconfigured through ROADMs. Consequently, due to high capital cost, to determine an optimal placement of ROADMs and to assign wavelengths in a cost efficient way becomes an important problem in network topology design. We introduce a Mixed Integer Programming model that captures signal loss and wavelength packing/blocking, and develop a three-phase algorithm to efficiently solve it. Analytical justifications for the algorithmic steps are provided. Computational experiments are conducted to assess the tractability of the model, and to evaluate the performance of the proposed approach. The execution times of the algorithm are acceptable.