There is the method whose details I explained earlier. Phase measurement is pretty easy, one simple method is to take your returned signal, via a filter tuned to the transmitter frequency, amplify, clip and compare to a similarly clipped signal derived from the transmitter. Start a timer on the falling edge of the transmitter. Stop it on a falling edge of the receiver. Phase is proportional to this time/ transmitter period. Repeat. Average. Next frequency. Drive the Laser with a PLL and have a divider in the loop, so the '52 can generate the references, and the PLL multiply the ref frequency for you.

Steve