Common-path spectral-domain optical low coherence interferometric system for the measurement of small changes in refractive index of Liquid Crystal cell

► A fiber-based common-path spectral-domain optical low coherence interferometer is realized. ► Spectral modulations as a function of applied voltage to liquid crystal cell are measured. ► Hilbert transform technique was used for the extraction of phase of the spectral interferograms. ► From spectral changes, small variation in refractive index of LC cell with voltage is determined.