Long-distance fibre-optic white light displacementsensing system using a source-synthesising technique

A long-distance fibre-optic white-light displacement sensing system, using a synthesised source generated by combining the outputs from two low coherence sources, is demonstrated. As the wavelengths of both sources are compatible with standard 1.3 µm singlemode telecommunication fibre, allowing the peak of the central fringe in interferogram to be determined precisely, a measurement range to resolution of better than 104:1 over a remote distance of 3.3 km has been achieved. It can be expected that this system could find important applications in long-distance, remote, and absolute measurements for quasistatic parameters.