A demodulation method and device for a distributed optical fiber vibration sensing system
A technology of vibration sensing system and distributed optical fiber, applied in the field of electronic information, to achieve reliable stability, simplified demodulation, and wide application prospects
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Embodiment 1
[0041] This embodiment is a further explanation and illustration of the demodulation method of the distributed optical fiber vibration sensing system, but it does not constitute any limitation to the present invention.
[0042] In this embodiment, a sensing optical fiber with a one-dimensional length of L meters is taken as the research object, and a position with a length of x meters from the processing end point is used as a measurement point. Assuming that within a certain period of time t, the backscattered Rayleigh light information sequence of the obtained measurement point after multiple digital averages of the hardware module is P 0 (x),P 1 (x),...,P j (x),...,P N (x).
[0043] According to the stepping stone method, the above sequence is processed to generate a subsequence A 0 (x),A 1 (x),...,A j (x),...,A M (x), where,
[0044] A 0 (x)=(P 0 (x)+P 1 (x)) / 2,A 1 (x)=(P 1 (x)+P 2 (x)) / 2,A 2 (x)=(P 2 (x)+P 3 (x)) / 2,....
[0045] A M (x)=(P N (x)+P 0 (...
Embodiment 2
[0053] The distributed optical fiber vibration sensing and demodulation device provided in this embodiment includes a laser drive assembly, an optical fiber circulator 3 , a photodetector assembly 5 and a microprocessor 6 .
[0054] The laser drive assembly includes a narrow linewidth continuous laser driver 1 and an external modulator 2 . The external modulator 2 converts the continuous laser light emitted by the narrow-linewidth continuous laser driver 1 into periodic pulsed laser light according to the start signal sent by the microprocessor, and injects the pulsed laser light into the sensing fiber through the optical fiber circulator 3 . The narrow-linewidth continuous laser driver 1 is a 3KHz TNK continuous solid-state laser. The external modulator 2 is a semiconductor amplifier with a frequency of C / (2nL), where C is the speed of light in vacuum, n is the effective refractive index of the optical fiber, and L is the length of the sensing optical fiber. The spatial reso...
experiment example
[0058] Using the demodulation method given in Example 1 and the demodulation device given in Example 2, the actual temperature measurement verification of the 5km vibrating optical cable connected in series on the steel wire mesh was carried out. Use a TNK continuous solid-state laser with a line width of 3KHz as a narrow line width continuous laser driver 1, a semiconductor optical amplifier as an external modulator 2, assemble a photodetector assembly 5, and use a pc104 as a microprocessor 6. The continuous laser light emitted by the TNK continuous solid-state laser with a line width of 3KHz is injected into the vibrating optical cable through the optical fiber circulator 3 through the semiconductor optical amplifier, and the returned backscattered Rayleigh information is received by the APD detector through the optical fiber circulator 3 and the optical signal is converted into electrical signal, and then the A / D conversion module converts the analog electrical signal into a...
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