Limitations to inverse problem based estimation of DGD in an optical fiber due to the use of the linear propagation model

In-work estimation of DGD of an On-Off-Keyed (OOK) optical fiber communication line directly from the transmitted can be advantageous for it does not necessitate neither dedicated measurement equipment nor modifications to the transmitter and the receiver. The concept is to use the inverse problem technique, i.e. to fit to the recorded received signal a suitably parametrized model of the response of the communication line using global optimization. In this procedure the model is evaluated many times hence, the use of the exact nonlinear propagation model can be prohibitive if the estimation result has to be provided timely. The paper proposes a method to assess inaccuracy of the DGD estimation in which the propagation model is replaced by the linear one and presents the results of the assessment. The practical limits for the application of the linear model can learnt. The outcome of the paper can be used as a source for design directions for in-work DGD monitoring systems for optical communications.