Long-distance fibre-optic white light displacement sensing 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 the 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