The Sensing Technical Research And Application Based On Fiber Grating Devices

In the Information Age, as an important technical foundation of modern society, the sensor plays a more and more important role. Fiber Bragg grating sensor is a outstanding representative of the passive sensor. This paper first introduces the development of fiber grating sensor and studies all kinds of fiber grating demodulation technique. And we found that the active sensing has some advantages that passive sensing does not have such as:high signal-to-noise ratio, high output power and ease of detection, etc. Considering of these shortcomings of passive sensing, in this paper we will make passive sensing upgrade to active sensing and propose optical fiber laser sensor, it not only retains the technical characteristics of the fiber grating sensor, but also overcomes the shortage of passive sensing technology at the same time.In the second chapter, we compare six kinds of wavelength of fiber grating sensor demodulation scheme and find that each demodulation has its flaws. Since there are more or less flaws existing in all the sensing schemes, we turn our gaze to the active fiber grating sensing technology. On the basis of passive sensing technology, the active sensing technology constantly developed, the Fiber Bragg grating in the passive sensing system is replaced by fiber laser and then active sensing system is formed. It can clearly improve the signal-to-noise ratio of the sensor, and the beat frequency demodulation technology convert the difficult-detecting wavelength signals into the beat frequency which can be detected in the electric field, which greatly reduces the difficulty of signal demodulation, so it is a very promising sensing technology.In the third chapter, fiber laser sensing technology based on beat frequency demodulation is proposed. Firstly we introduced the principle of multi-longitudinal-mode fiber laser sensing, and the principles of the beat signals generated between multi-longitudinal mode patterns and patterns, and we proved that mode hopping phenomenon almost has no effect on the detection result of such sensors through experiments. In the three experiments, through analyzing the principle of a physical quantity acting on the resonator, we can not only realize a single physical quantity signal measurement, but also achieve two physical quantities detection at the same time by detecting the longitudinal mode beat frequency and polarization-mode beat frequency signal. In addition, we also studied and discussed how to choose the best beat frequency signal from a large number of beat frequency signals generated in the multi-longitudinal-mode fiber laser sensor, the signal we choose should has high sensitivity and high signal-to-noise ratio at the same time. In the fiber laser sensor system, the beat frequency demodulation method is a very simple and full-electronic optical signal demodulation technique. The simple and inexpensive frequency-meter is able to achieve high-precision of demodulation, and it can reduce the cost of the sensor largely. In brief, the optical fiber laser sensor based on beat frequency demodulation has broad market prospects.