Embodiments of the invention provide multi-channel OCT (Optical Coherence Tomography) for imaging biological tissue, and for temperature and/or force sensing, preferably in real time. In one embodiment, an optical signal processing system comprises: a processor; a memory; a receiving module to receive in real time input from multiple channels of OCT producing interfering optical signals representing multiple measured distances for a target imaging object; a Fast Fourier Transform (FFT) module to apply FFT on the interfering optical signals in real time to produce Fourier frequencies corresponding to the multiple measured distances; and a calculation module to calculate in real time multiple force components of a force applied on the target imaging object to cause at least some of the multiple measured distances for the target imaging object based on the Fourier frequencies from the FFT module.