【作者】 毕婕；

【导师】 忻向军；

【作者基本信息】 北京邮电大学 ， 光学工程， 2012， 硕士

【摘要】 光纤光栅作为一种新型传感器,有成本低、重量轻、灵敏高等优点,因此在许多领域广泛应用[1]。本文提出并研究了一种基于有源可调谐环形光纤激光器的多通道光纤光栅传感解调系统,可实现32通道超过1000个光栅的实时监测。系统利用有源可调谐环形激光器作为扫描光源,用电压信号控制可调谐F-P滤波器,实现对多支路光纤光栅传感器阵列扫描。采用光纤梳状滤波器代替传统的参考光栅阵列,作为单独的校准支路实现波长的标定和校准,由于梳状滤波器体积小,对温度漂移不敏感,因此降低了F-P滤波器的温度漂移、非线性和蠕动性对测量精度的影响,与传统定标方法相比,光纤梳状滤波器的精度高,易操作,比较适合工程应用[16]。这种方案解决了传统波长扫描方案复用率低,定位与定标困难、系统成本高等问题,增加了系统复用传感光栅的数量,降低了单位光栅的检测成本。实验结果表明,光源输出的光功率大幅提高,扫描光源的线宽很窄,波长范围在1525-1585nm,对于32路的复用结构,可复用的光栅数目较传统宽带光源法大大增加,每路能达到30-50个FBG,整个系统可检测超过1000个光栅。根据监测距离的长短,系统可以在1秒钟对所有FBG实现100次测量。本文还针对这种多通道解调系统,提出了一种3dB中点波长解调算法,同时将数字信号处理技术运用于光信号解调。通过实验研究,分析该快速算法对信号的解调效果,比较了多种算法的精度。研究发现,在多通道光纤光栅传感实验系统中,该算法有效地降低了寻峰算法中输入信噪比对系统解调精度的影响,分辨率为0.1pm,解调精度可达2 pm,即应变测量精度可达1με,温度测量精度可达0.1℃。因此,该解调系统高精度大范围的性能特点,可以很好地适用于实际工程应用,具有较高的市场价值。更多还原

【Abstract】 Fiber Bragg gratings (FBGS) have been widely applied as the sensing elements, which have a low cost, light weight and high detection sensitivity. To improve the capability and detection precision of the Fiber Bragg sensing system, the novel interrogation technique and detection algorithm based on the tunable ring laser and multiplexing technology are proposed for the multi-channel Fiber Bragg grating sensing system, which can realize the real-time monitoring of 32 channels more than 1,000 FBG sensors. In the scheme, a tunable optical filter controlled by a scanning voltage is used to scan through the working range of FBG spectra and detect the peak wavelength of each FBG sensor in multi-channels. Here, we use the comb filter as multi-wavelength reference instead of the traditional reference grating array. Because the small comb filter isn’t sensitive to the temperature, the factors of temperature drift, nonlinear, and peristalsis can be greatly reduced, the measurement accuracy is greatly improved. Experimental results show that the power of laser source is improved greatly and has a narrow width. With the combination of the numerical simulation and experiment, it is demonstrated that the average precision of interrogation is improved over the working range of 1525-1585 nm. The system can realize the real-time monitoring of 32 channels more than 1,000 FBG sensors. In the experimental system, the reflection spectra of the FBG sensors in the multi-channel FBG system are recorded for 100 times within 1 minute. Moreover, a fast wavelength detection algorithm based on the half-power point is proposed. The present work shows that the algorithm described in this paper can reduce the signal noise ratio (SNR) at the input of the system which influences the precision of interrogation. Compared to other schemes, the interrogation method is greatly improved in the measurement precision, wavelength range, and working reliability. The resolution is 0.1pm and interrogation accuracy is 2pm, which means the strain measurement accuracy is 1μεand the temperature measurement accuracy is 0.1℃.The system of a wide scale and high precision can be well applied to practical engineering applications.更多还原