High-Performance Low Coherence Interferometry Using SSB Modulation

Low coherence interferometry (LCI) is an optical measurement technique that has attracted the interest for relevant fields like medicine or sensing. With the objective of improving LCI capabilities, microwave photonics (MWP) arises as an innovative technology to enhance LCI possibilities. In this letter, a novel MWP-LCI approach is proposed and experimentally demonstrated to measure the optical path difference (OPD) of a sample. The operation principle of the technique is based on the analysis of the interference pattern through a dispersive element to retrieve its visibility using a vector network analyzer. Different capabilities of the system in terms of sensitivity, resolution, and SNR have been proved. In this case, the proposal is able to avoid carrier-suppression effect leading to a sensitivity improvement of 20 dB in comparison with previous structures for certain values of the OPD. Moreover, the OPD range has been extended up to 10 mm achieving an invariant resolution over all operation range. Finally, the improvement of the SNR of the system has been experimentally demonstrated by controlling properly the RF resonance profile through the adjustment of the optical source power distribution. We have observed an improvement of the dynamic range close to 40 dB for a Gaussian profile.