A circuit for generating a swept source optical coherence tomography (SS-OCT) imaging calibration clock. The circuit comprises a first photodetector configured to convert an SS-OCT optical calibration signal to an SS-OCT electrical calibration signal, a first analog-to-digital converter (ADC) coupled to the first photodetector and configured to convert the SS-OCT electrical calibration signal to a sequence of SS-OCT calibration signal digital values, a processing unit coupled to the first ADC that, when initiated, is configured to demodulate the sequence of SS-OCT calibration signal digital values to obtain a sequence of SS-OCT wave number digital values, where each SS-OCT wave number digital value corresponds to one of the SS-OCT calibration signal digital values, and a level crossing sampler that is configured to track a wave number associated with the SS-OCT optical calibration signal and to generate an SS-OCT calibration clock pulse.