Optical synthesis of frequency-tracking signals employs square-law based frequency conversion of pairs of optical signals having a predetermined, relative frequency shift to provide output signals. An optically synthesized tracking signal source includes a square-law photodetector configured to provide a first output signal having a frequency equal to a frequency difference between a first optical signal pair. Another square-law photodetector is configured to provide a second output signal having a frequency equal to a frequency difference between a second optical signal pair that is a frequency-shifted version of the first pair. The signal source further includes an optical wavemeter configured to determine one or both of the first pair frequency difference and the second pair frequency difference. The first and second output signals are tracking signals having a frequency offset determined by a relative frequency shift between the first and second pairs of optical signals.