Optical coherence tomography (OCT) imaging is used in an increasing number of biomedical and industrial applications. A massively parallel simulator of OCT of inhomogeneous turbid media, e.g., biological tissue, could be used as a practical tool to expedite and expand the study of the physical phenomena involving such imaging technique, as well as, to design OCT systems with enhanced performance. Our work presents the open-source implementation of this massively parallel simulator of OCT to satisfy the ever-increasing need for prompt computation of OCT signals with accuracy and flexibility. Our Monte Carlo-based simulator uses graphic processing units (GPUs) to accelerate the intensive computation of processing tens of millions of photon packets undergoing a random walk through a sample. It provides computation of both Class I diffusive reflectance due to ballistic and quasi-ballistic scattered photons and Class II diffusive reflectance due to multiple scattered photons. Our implementation was tested by comparing results with previously validated OCT simulators in multilayered and inhomogeneous (arbitrary spatial distributions) turbid media configurations. It models the objects as a tetrahedron-based mesh and implements and advanced importance sampling technique. Our massively parallel simulator of OCT speeds up the simulation of OCT signals by a factor of 40 times when compared to it central processing unit (CPU)-based sequential implementation.