A summed source-synthesis approach to low coherence interferometry (LCI) involving three low coherence sources is described. Simple modelling suggests that this scheme should provide a much more distinct central fringe in the presence of electronic noise than LCI using a single or double wavelength light source. This has been demonstrated experimentally using an all-fibre tandem LCI sensor with a Fabry-Perot sensing interferometer and a Michelson receiving interferometer. Simple optical peak detection and central fringe analysis were used to locate the path matching condition, allowing real-time tracking of temperature and strain variations in the sensing interferometer.