High-Speed and High-Resolution Low-Coherence Interferometric Demodulation Without Phase Jumps

This letter reports a high-speed and high-resolution low-coherence interferometric demodulation algorithm without phase jumps. The demodulation algorithm utilizes the restored analytic interference signal and discrete Fourier transform to deduce the Buneman frequency estimation formula and obtain the linear phase. The optical path difference (OPD) is demodulated based on the Buneman frequency estimation and total phase method. Phase jump is eliminated by re-calculating the peak index and phase from the amplitude and phase frequency spectrums when the peak index approximates an integer value. The experimental results verify the phase jumps are eliminated. The proposed demodulation algorithm provides a 0.027-nm cavity length resolution of an extrinsic Fabry-Perot interferometer (EFPI) with 5-kHz demodulation rate and 384 data points number of an optical spectrum. The speed limitation experimental results show the demodulation speed can achieve 300 kHz with 256 data points number of an optical spectrum. The proposed demodulation algorithm is very robust and promising for all kinds of low-coherence interferometers.