Methods and apparatus to control the optical frequency of a laser are disclosed. An apparatus includes: a first laser to emit a first beam of light, the first beam of light to have an adjustable frequency based on an input current; a second laser to emit a second beam of light, the second beam of light to have a substantially fixed frequency; a photodetector to generate a feedback signal indicative of a frequency difference between the first and second beams of light; and logic circuitry to control the input current based on the feedback signal.