Novel extended lissajous figure based location method for fiber-optic distributed disturbance sensor

A location method based on the extended Lissajous figure was proposed for fiber-optic distributed disturbance sensor based on Mach-Zehnder interferometer. The disturbance was located by the fiber-optic distributed disturbance sensor due to the time delay between the two signals from clockwise and counter- clockwise Mach-Zehnder interferometer. In the Lissajous figure of the two signals, a fitting ellipse with constant semimajor and azimuths was induced to evaluate the time delay. The relationship between the time delay and semiminor of the ellipse was obtained by linear fitting. Then, the time delay could be calculated by the semiminor of the fitting ellipse. By the simulation with experimental data and experimental test, it is found that the proposed lower location errors can be obtained by the location method than current cross correlation function based method without phase generation carrier technique.