Common-mode phase noise suppression with an open-loop differential phasemeter

We present direct differential phase recovery-an open-loop phasemeter topology for differential optical interferometric measurements. The technique aims to remove common mode signal dynamics prior to phase-tracking, which reduces the dynamic range requirements of the phasemeter tracking optical phase differences. A phase difference measurement is experimentally demonstrated with this technique, achieving a phase sensitivity of 1 × 10^-6rad/Hz with a common-mode noise rejection of 141 dB. We demonstrate this performance whilst individual channels are subject to numerous cycle slips and unable to track phase.