Phase-sensitive swept-source interferometry for absolute ranging with application to measurements of group refractive index and thickness.

Interferometric range measurements using a wavelength-tunable source form the basis of several measurement techniques, including optical frequency domain reflectometry (OFDR), swept-source optical coherence tomography (SS-OCT), and frequency-modulated continuous wave (FMCW) lidar. We present a phase-sensitive and self-referenced approach to swept-source interferometry that yields absolute range measurements with axial precision three orders of magnitude better than the transform-limited axial resolution of the system. As an example application, we implement the proposed method for a simultaneous measurement of group refractive index and thickness of an optical glass sample.

Correction of sampling errors due to laser tuning rate fluctuations in swept-wavelength interferometry.

The frequency-sampling method is widely used to accommodate nonlinear laser tuning in swept-wavelength interferometric techniques such as optical frequency domain reflectometry (OFDR) and swept-wavelength optical coherence tomography (OCT). In this paper we analyze the frequency-sampling method and identify two sources of sampling errors. One source of error is the limit of an underlying approximation for long interferometer path mismatches and fast laser tuning rates. A second source of error is transmission delays in data acquisition hardware. We show that the measurement system can be configured such that the two error sources cancel to second order. We present experimental verification of sampling error correction using a general swept-wavelength interferometer with a significantly nonlinear laser sweep.