Dispersion engineering of waveguides in photonic integrated circuits (PIC) is a crucial design tool for tailoring nonlinear functionalities in the rapidly emerging thin film LiNbO3 (TFLN) platform, exemplified by frequency comb generation, soliton formation and broadband frequency conversion [1]. Experimentally, the dispersion of PIC structures is typically measured in terms of free-spectral range (FSR) variation in ring cavity configurations or propagation time delays in long waveguides under short pulse excitation [2], methods with their own limitations when it comes to measurements in straight and relatively short (< cm) waveguides, such as TFLN ones.