Methods and apparatus for local oscillator generation are provided. In a method embodiment, a method of signal processing includes splitting a signal having a first frequency into at least a first portion and a second portion. The method also includes generating a second signal having a second frequency at a predetermined frequency difference from the first frequency by optically modulating the first portion. In addition, the method includes generating a third signal having a frequency component at a frequency that is approximately the same as the predetermined frequency difference from the first frequency by combining the second portion with the second signal.