Method and device for frequency domain optical fiber optical grating sensing network demodulation

Abstract

The invention relates to a method and a device for demodulating a frequency domain fiber grating sensing network. In the invention, an electro-optic modulator is connected with a Sagnac loop; an FBG sensing network formed by connecting a plurality of sensing FBGs in series is connected with the Sagnac loop by a three-port 3-dB fiber coupler; the bragg wavelengths of each reference FBG on a reference FBG array are the same as the sensing FBGs with same sequence numbers. The electro-optic modulator is driven by a RF signal with variable frequencies. When the frequencies of the RF signal are changed, the change of the transmittance is detected by a photodiode; the drift amount of the bragg wavelengths of each sensing FBG on the sensing network is obtained by carrying out fast Fourier transformation and relevant operations on the output data of the photodiode collected by a collecting card, and finally the change of the sensed physical quantity is obtained. The invention can have an extremely high response speed for meeting the requirements of real time sensing; besides, as the sensing network is connected with the Sagnac loop, the performances of anti-external temperature fluctuation and anti-mechanical disturbance of the device are high.

Description

technical field [0001] The invention belongs to the technical field of optical fiber sensing, and is applicable to the field of real-time sensing network requiring multi-node, high precision and anti-electromagnetic interference, and in particular relates to a method of using an electro-optical modulator to change the frequency of light waves to cause a Sagnac ring The effect of structural asymmetry and the method for realizing FBG sensor network demodulation by fiber Bragg grating (FBG) hypotenuse detection technology and the equipment for realizing the method. Background technique [0002] FBG has become an important device for optical fiber sensing due to its unique advantages of optical fiber internal sensitivity, wavelength coding, and easy networking. Based on the developed wavelength division multiplexing (WDM) and time division multiplexing (TDM) technologies, fiber grating arrays are widely used in optical fiber quasi-distributed sensing, such as: health monitoring ...

AI Technical Summary

Problems solved by technology

Both sets of multiplexing technologies require high-cost light sources and complex demodulation systems, which directly lead to the high cost of the FBG sensor network and limit many of its practical applications.

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