Absolute distance measurement using frequency-sweeping heterodyne interferometer calibrated by an optical frequency comb

Abstract

We present a frequency-sweeping heterodyne interferometer to measure an absolute distance based on a frequency-tunable diode laser calibrated by an optical frequency comb (OFC) and an interferometric phase measurement system. The laser frequency-sweeping process is calibrated by the OFC within a range of 200 GHz and an accuracy of 1.3 kHz, which brings about a precise temporal synthetic wavelength of 1.499 mm. The interferometric phase measurement system consisting of the analog signal processing circuit and the digital phase meter achieves a phase difference resolution better than 0.1 deg. As the laser frequency is sweeping, the absolute distance can be determined by measuring the phase difference variation of the interference signals. In the laboratory condition, our experimental scheme realizes micrometer accuracy over meter distance.

Absolute distance measurement by dual-comb nonlinear asynchronous optical sampling

“…In the first place, the absolute distance is calculated by synthetic wavelength method with continuous wave (CW) lasers as the light source. The optical frequency comb is adopted as frequency standard for CW wavelength calibration [5][6][7][8]. In a simplified measurement, synthetic wavelengths are considered to be directly generated by heterodyne beatings among optical frequency components within the comb bandwidth and the absolute distance is measured through phase analysis of these heterodyne frequencies [9].…”

Algebraic solution for phase unwrapping problems in multiwavelength interferometry

“…This is achieved without the need for closely separated measurement wavelengths. The results of this work have numerous applications in absolute distance metrology [20,21,[27][28][29], discrete wavemeters [30,31], and full-field MWI and profilometry techniques [7-9, 22, 24,32], or multi-wavelength digital holography [33][34][35]. Fig.…”

“…The limitation of this fibre optical design lies in the wavelength stability in λi that is determined by the stability of the FBGs and the accuracy of the optical spectrum analyzer (OSA). A detailed analysis can be found in reference [12] (and is summarized in section 5); this indicates the tremendous improvement that can be made if the measurement wavelengths are extracted from a frequency-comb [19][20][21]. Nevertheless, in this configuration, a UMR of 2 multiples of the longest beat has been obtained.…”

Operation of an optically coherent frequency comb outside the metrology lab

“…The advent of a new generation of mobile atomic clocks [16,17] and comb-based free-space optical frequency transfer [18] could permit precise timing networks, tests of relativity, and clock-based geodesy [19,20]. Finally, the precision and accuracy of comb-based LADARs are attractive for manufacturing and remote sensing in general [21][22][23][24][25][26][27][28][29][30]]. Here we demonstrate a self-referenced fiber frequency comb that can operate in the field while retaining its optical coherence and 5 femtosecond-level timing-jitter.…”