The dataset provides the data supporting the research project of longitudinal power monitoring for characterising the ODN in PONs using simplified coherent receivers. The data includes the power profiles estimated for both single-loss and multiple-loss events, the model selection data based on the Bayesian Information Criteria, the experimental power budget data, and the simulation results for the investigation of regularisation and signal-to-noise ratio. The power profiles data contains the Matlab simulation and experimental results obtained using the regularised linear least squares and the fitted ones with the piecewise linear fitting. The experimental data was collected in the setup of 60 GBd 16 QAM downstream transmission with a 60 km fibre link using the simplified coherent receiver.