We experimentally demonstrate a simple method to characterize the temporal dynamics of the power transfer matrix of a mode division multiplexed (MDM) system using the time series of the output power in each channel. We consider a 3 × 3 MDM system consisting of a pair of 3-channel photonic lanterns (PL) for mode (de)multiplexing and 1 km of few-mode fiber (FMF) to evaluate the time evolution of channel selectivity, insertion loss, channel-dependent loss, and accumulated cross-talk for each channel. We further compare the statistics of time evolution of the above parameters for MDM systems utilizing mode-selective and non-mode-selective photonic lanterns. Such results are used to evaluate the consequences of choice of photonic lanterns and their utility in long-haul and short-reach mode division multiplexed systems.