Research on Fiber Sagnac Vibration Sensor Based on Multi-mode Fiber Coupler
The traditional fiber optic vibration sensor has a limited range of measurable vibration fre-quencies.To further improve the frequency recognition ability of the fiber optic vibration sensor,a multi-mode fiber(MMF)coupler is used to construct a Sagnac interferometer.Combining multi-mode interference with Sagnac interference,a new Sagnac interferometric vibration sensor structure based on multi-mode interference for measurable vibration frequencies is proposed.Using MMF with core diam-eters of 105 μm and 62.5 μm,multi-mode fiber couplers with a splitting ratio of 1∶1 are fabricated,and Sagnac loops are constructed by using them.For comparative analysis,sensors with single mode-multi-mode-single mode(SMS)interference structure and Mach Zehnder interference structure are fabricated using MMF.A detailed comparative study is conducted on several types of vibration sensors in terms of vibration frequency detection range,vibration frequency detection accuracy,and vibration signal amplitude through extensive experiments.The research results show that the Sagnac interferomet-ric structure based on the 105 μm core diameter step refractive index distribution MMF achieves fre-quency recognition in the frequency range of 0.3～20 kHz with a difference in intensity between the main and secondary peaks of the spectrum greater than 20 dB.It has a wide measurable frequency range,a large difference in intensity between the main and secondary peaks,and is more sensitive to low-frequency vibrations.The frequency deviation is in the Hz range,and it has the best vibration test-ing performance among several comparative structures,providing a new solution for vibration detection research.
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维普
