Spectral difference interferometry for the characterisation of optical media

We propose and demonstrate a new form of interferometry combining high phase sensitivity and excellent mechanical isolation. These features arise from maintaining a probe and reference tone in the same medium under test at all times, their ultimate homodyne detection, as well as a novel method employing an optical programmable filter which is used to extract their relative phase difference. We present a compilation of studies performed to illustrate the applicability of the scheme to a range of measurements of optical propagation characteristics. Measurements include the chromatic dispersion of SMF-28 of lengths ranging from 1m to 1km, the nonlinear coefficient of highly nonlinear fibre and the phase transfer profile of an integrated optical ring resonator