An Extrinsic Fabry-Perot Interferometric (EFPI) fiber optical sensor system is an online testing system for the gas density. The system achieves the measurement of gas density information mainly by demodulating the ca...An Extrinsic Fabry-Perot Interferometric (EFPI) fiber optical sensor system is an online testing system for the gas density. The system achieves the measurement of gas density information mainly by demodulating the cavity length of EF- PI fiber optical sensor. There are many ways to achieve the demodulation of the cavity length. For shortcomings of the big intensity demodulation error and complex structure of phase demodulation, this paper proposes that BP neural net-work is used to locate the special peak points in normalized interference spectrum and combining the advantages of the unimodal and bimodal measurement achieves the demodulation of the cavity length. Through online simulation and actual measurement, the results show that the peak positioning technology based on BP neural network can not only achieve high-precision demodulation of the cavity length, but also achieve an absolute measurement of cavity length in large dynamic range.展开更多
文摘An Extrinsic Fabry-Perot Interferometric (EFPI) fiber optical sensor system is an online testing system for the gas density. The system achieves the measurement of gas density information mainly by demodulating the cavity length of EF- PI fiber optical sensor. There are many ways to achieve the demodulation of the cavity length. For shortcomings of the big intensity demodulation error and complex structure of phase demodulation, this paper proposes that BP neural net-work is used to locate the special peak points in normalized interference spectrum and combining the advantages of the unimodal and bimodal measurement achieves the demodulation of the cavity length. Through online simulation and actual measurement, the results show that the peak positioning technology based on BP neural network can not only achieve high-precision demodulation of the cavity length, but also achieve an absolute measurement of cavity length in large dynamic range.
文摘局部放电超声阵列定位技术是将传感器阵列与阵列信号处理方法相结合。文章采用非本征法布里帕罗干涉(Extrinsic Fabry-Perot Interferometric,EFPI)的光纤超声传感器,其灵敏度高,不受电磁干扰的影响,并充分发挥EFPI传感器可放置于油中的优势,改进阵列结构。设计了4阵元EFPI超声传感器正四面体结构阵列,将其置于油箱内部检测局放超声信号,利用多信号分类算法(Multiple Signal Classification,MUSIC)对局放源进行测向,并与平面2×2阵列进行对比,针对阵元位置误差进行校正。结果表明该阵列传感器能够在油中检测到信噪比较高的局部放电信号,且较传统平面阵具有更高的测向准确度;尤其在阵列盲区方面,立体型阵列传感器可有效地实现空间多角度的信源测向。利用TCT算法对阵元位置误差进行校正,提高了测向精度,满足了实际工程需要。
