Optical signaling is implemented by modulating visible light with variable pulse position modulation (VPPM). VPPM is a composite waveform and its optical signal includes a Start Frame Delimiter (SFD) which indicates start of optical signaling. To identify modulated lights, the duty cycle is periodically changed in the waveform to induce an AM envelope at a frequency higher than the response of the human eye. The signal is then sampled via a camera producing an alias frequency that produces noticeable blinking. Because the communication is asynchronous, the desired camera frame rate (fc) in relationship to the modulation bit rate timing clock (or symbol rate, fs) is only approximate. Consequently, a frequency offset develops between the camera frame rate (fc) and the symbol rate (fs) in transmission of long packets. The disclosed embodiments provide a detection algorithm, system and apparatus to provide clock offset tracking and correction.