New method to obtain optimum performance for 100Gb/s multi-span fiber optic lines

Abstract

Design of DWDM lines requires calculation of optimal input powers for each span. It is called “optimization of DWDM network”. Different approaches are currently used to solve this task including maximization of optical signal-to-noise ratio (OSNR) margin and minimization of bit error rate (BER). Within last years there is a particular interest to DWDM lines based on uncompensated links with coherent transmission. We analyze benefits and drawbacks of existing approaches and offer a new method of optimization that guarantees sufficient OSNR margin for bringing into service such DWDM lines.The proposed method combines the advantages of two previously known methods. For short lines, it works like BER criterion. It does not overestimate values of power, and does not require the recalculation after each stage of expansion of the line. For long lines, it works like OSNR margin criterion. It guarantees that calculated values of powers will enable bringing the line into service; and if the optimization is failed it means that it is impossible to commission the line by any other method.Discussion and comparison of different methods are based on a general phenomenological model for multi-span fiber optic line that takes into account both linear and nonlinear noises. The proposed phenomenological model is a consequence of the GN model where a number of parameters characterizing nonlinear interaction of DWDM channels are determined experimentally.