System and method for increasing coherence length in lidar systems

A system for compensating for a phase variance at a laser source comprising:

• a phase difference detector configured to receive a reference arm signal and to detect a phase difference of the reference arm signal, the phase difference corresponding to a difference in the phase of the reference arm signal at two points in time;
• a phase correction estimator configured to receive the phase difference from the phase detector and to estimate a phase correction to be applied to a target arm signal;
• a phase modulator configured to receive the phase correction from the phase correction estimator, to modulate the target arm signal with the phase correction, and to output a phase corrected target arm signal, wherein the phase correction compensates the target arm signal for the phase variance of the laser source;
• and
• a delay coupled either to either the reference arm signal and configured to introduce a delay time into the reference arm signal prior to being received by the phase difference detector or to the target arm signal prior to being received by the phase modulator, wherein
• the delay time comprises at least a round trip path delay.