| Since twenty-first century, with the rapid development of information technology, the monitoring on a variety of engineering structures, mechanical structures and natural disasters such as earthquake become more highly dependent on the analysis and solution of complex vibration. Traditional electromagnetic vibration sensors in the aspects of sensitivity, accuracy, dynamic-range, anti-electromagnetic interference and so on, can no longer meet the application requirements. Therefore, the research and exploitation of new and higher quality vibration sensors has become particularly important. Except of having the function of traditional electromagnetic sensor the optical fiber vibration sensor has the virtue of against electromagnetic interference and atomic radiation, high sensitivity, high measurement speed and good stability and so on. So it is widely applied in many fields such as aviation, aerospace, bridges, civil construction.In this paper, summarized the current development of domestic and international optical fiber vibration sensors, then a novel structure of vibration sensor based on FBG is proposed. The innovations of this structure are self-demodulation technology of the matched FBG is applied into the optical fiber vibration sensor and side hole packaging technology is applied to package the matched FBG. The details are described as follows:(1) Vibration testing, advantages of the general optical fiber sensor, features of the FBG sensors are introduced, then several general FBG vibration sensors are briefly introduced.(2) The principle of the optical fiber sensor and FBG vibration sensor are elaborated. The model of FBG strain sensor under uniform axial stress and under uniform horizontal stress are analyzed theoretically; Current domestic and international sensitization technology and packaging technology of the FBG vibration sensors are analyzed separately; A novel structure of FBG vibration sensor is proposed based on the principle of FBG vibration sensor and current sensitization and packaging technology of the optical fiber vibration sensors, and the design principle of the structure are discussed in detail, then the structure scheme is analyzed theoretically by mathematical formula and simulation of Matlab.(3) The structure of the proposed scheme is simulated by optiamplifier. Since no equivalent excitation with vibration signal, it is impossible to probe to the FBG directly. We can only adjust the interval of the two FBG center wavelength to simulate the effect of the external vibration signal by entering the value manually in the process of simulation. Put the data from the simulation in a list and process the data to get the relationship between the offset of the two FBG center wavelength and the output light intensity by Matlab, the structure scheme is validated correct due to the relationship is consistent with that from the theoretical analysis.(4) The structure of the proposed scheme is verified by experiment. In the present experimental conditions, we can only replace the packaged FBG with bare FBG. The two FBG with an optical adhesive are fixed on the up and down of the cantilever and will move to opposite direction under the same stress. The spectrometer will detect the output value of the light intensity. Put the data from the experiment in a list and get the relationship among the stress value, offset of the center wavelength and the output light intensity, then process the data to get the relationship between the offset of the two FBG center wavelength and the output light intensity by Matlab, the structure scheme is validated feasibility due to the relationship is consistent with that from the theoretical analysis.The packaging technology for FBG mentioned in this paper will implement in the next stage. I hope that the novel structure scheme of the optical fiber vibration sensor mentioned in this paper and researches from this paper could provide worthy theories and the technique support for further research and development of the optical fiber vibration sensor. |
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