Since the 1990s, fiber optic sensing technology based on Bragg gratings has received extensive attention from scientists and a lot of research has been conducted. Although USB clicker laser pointer the current large-scale, fast and cheap grating production technology and its process are mature, the more expensive laser pointer optical demodulation equipment still limits its wide application in a series of important fields such as industry, chemical industry and building structure inspection. .
In addition, compared with the traditional optical domain demodulation method, the demodulation method that uses an optical filter to convert the drift of the grating wavelength into a change in power has the advantages of low cost, simplicity, and fast response speed. Prior to this, the research group led by Associate Professor Xia Li of the Department of Optical Communications and Optical Networks used cross-Gaussian filtering to achieve fiber grating sensor demodulation, and the research results have been published in journals. With the deepening of research, it is found that this method has two disadvantages: one is that two additional filters with Gaussian filtering characteristics are needed, which increases the complexity of the system; the other is that the power spectrum density of the broad-spectrum light source used is small. , Making the sensor demodulation distance and range limited.
Therefore, the research team has further designed a weak fiber grating sensor array demodulation method based on the incidence of a dual-wavelength narrow linewidth green laser pointer in its recent work. At the input end of the demodulation system, two lasers with a certain center wavelength interval are used for incidence. Using the Gaussian spectrum characteristics of the weak reflection fiber grating and detecting the power difference, a linear Bragg wavelength to power difference conversion can be obtained. And the slope of their linear relationship can be adjusted simply by controlling the wavelength interval of the dual-wavelength laser.
This method does not require the filter characteristics of the filter like the Gaussian matched filtering method, so the entire demodulation system is relatively simple. According to the current narrow linewidth laser pointer, the output power of the light source can easily reach more than 10dBm. This method can support a sensing demodulation distance of more than 50km without relay amplification, and can reach more than one optical fiber. Up to hundreds of weak anti-gratings are simultaneously demodulated. It can be predicted that this method will have very good application prospects in various fields of Bragg grating quasi-distributed sensor networks.