The detection abilities of PGC scheme dealing with the single frequency signal are investigated, based on which, the
frequency domain of the signal is analyzed. Based on the Bessel function theoretic, the mathematical model has been
established to analyze the performance of interferometric fiber-optic sensor under the PGC demodulation scheme. The
spectrums of interferometer output signals are analyzed when the input signal is single frequency signal and multifrequency
signal. Simulation results show that the dynamic domain upper limit of fiber-optic sensor when it operates with the multi-frequency signal must be much smaller than that it operates the single frequency signal.
An intensity modulated optical fiber accelerometer is designed. It can be applied in the real-time measurement of dynamic vibration acceleration. The theoretical analysis shows that the relation between the light intensity and displacement can be indicated by the same expression just with the difference in coefficient, though models of the fiber-optic intensity distribution at launching fiber end are different, such as Gaussian distribution, uniform distribution and those midst the upper two. Because of the simpleness of the expression, by means of specific linearization processing for the modulating function, a real-time and undistorted acceleration signal can be obtained.
A particular compensation is adopted to avoid the effect due to the static drift of the original distance between the launching fiber end and the reflective surface.
A novel scheme of a fringe count interferometric accelerometer is proposed. In view of practicability, the sensor must be made up of only fiber. Two 3dB directional couplers and singlemode fibers are used in this scheme to compose an imbalance Mach-Zehnder interferometer.
Phase modulation is achieved by modulating LD frequency to scan the interference fringes. With special technique, only one PIN is needed to count and identify the moving direction of the interference fringes. The signal can be transmitted more than several kilometers in a pair of fibers.
The two arms of the interferometer work at push-pull mode, which is favorable for temperature compensation. The resolution is significantly improved by fringe sub-division. A real-time dynamic vibration signal can be measured without distortion by this system.