Towards a stabilized Kerr optical frequency comb with spatial interference.

We measured a soliton's carrier frequency created by a silicon nitride Kerr comb from an interference pattern created by a spatial interferometer. The optical frequencies were determined from the interference pattern by simultaneously calibrating against an interference pattern from the pump optical frequency. Results were compared to real-time measurements by an optical spectrum analyzer (OSA). The spatial interferometer and the OSA results tracked each other, and the resulting RMS error is presented.