Zhang Naihan, Wang Muguang, Wu Beilei, Han Mengyao, Zhang Jing, Liu Yan, Fan Guofang
Opt Express. 2021 Nov 22;29(24):38989-39000. doi: 10.1364/OE.440551.
An optoelectronic oscillator (OEO)-based fiber optic current sensor (FOCS) with greatly improved sensitivity is proposed and experimentally demonstrated. A microwave photonic filter (MPF) induced by the dispersion effect of a linearly chirped fiber Bragg grating (LCFBG) is used to select the frequency of the OEO oscillating signal. A two-tap MPF formed by a polarization multiplexed composite cavity is cascaded to achieve a stable single mode oscillation. When the current changes, the magneto-optic phase shift induced by Faraday effect will be introduced between the left and right circularly polarized lights transmitted in the reflective sensing unit. The magneto-optic phase shift is converted to the phase difference between the optical carrier and sidebands through a LiNbO Mach-Zehnder modulator. This phase difference is the decisive factor for the center frequency of the cascaded MPF as well as the oscillating frequency. Therefore, the current can be measured in the microwave frequency domain, which can improve the interrogation speed and accuracy to a large extent. The experimental results show that the oscillating frequency shifts up to 407.9 MHz as the current increases by 1 A.
提出并通过实验验证了一种基于光电振荡器（OEO）的光纤电流传感器（FOCS），其灵敏度有了极大提高。利用线性啁啾光纤布拉格光栅（LCFBG）的色散效应诱导的微波光子滤波器（MPF）来选择OEO振荡信号的频率。由偏振复用复合腔形成的两抽头MPF级联以实现稳定的单模振荡。当电流变化时，在反射传感单元中传输的左旋和右旋圆偏振光之间会引入由法拉第效应引起的磁光相移。磁光相移通过LiNbO马赫-曾德尔调制器转换为光载波与边带之间的相位差。该相位差是级联MPF中心频率以及振荡频率的决定性因素。因此，可以在微波频域中测量电流，这可以在很大程度上提高询问速度和精度。实验结果表明，当电流增加1 A时，振荡频率最多偏移407.9 MHz。
