DeepFMKit simulates, processes, and analyzes data from Deep Frequency Modulation Interferometry experiments. The package offers a detailed physics engine that models time-of-flight delays, dynamic path length changes, user-prescribed colored noise sources via amplitude spectral densities, and arbitrary laser modulation waveforms. It includes modular, interchangeable fitting algorithms, notably a parallelized frequency-domain non-linear least-squares fitter and a time-domain extended Kalman filter for real-time state tracking. DeepFMKit supports large-scale parameter sweeps and Monte Carlo studies through a declarative experimentation framework and supplies tools for data handling, configuration management, and visualization of simulated and analyzed results.