A long-distance fiber-optic white-light displacement sensing system, using a synthesized 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 micrometer single-mode telecommunication fiber, allowing the peak of the central fringe in interferogram to be determined precisely, a measurement range to resolution of better than 10$+4$/:1 over a remote distance of 3.3 km has been achieved. Optimum synthetic source is also proposed to further reduce the SNR requirement for identification of the peak of the central fringe. It is expected that such a system could find applications in long-distance, remote, and absolute measurements for quasi-static parameters.
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