Fiber Bragg grating (FBG) demodulation based on microwave photonics (MWP) would have a high resolution but the measurement range is usually limited. Here, we propose an FBG demodulation system based on wavelength to optical fiber relative delay (OFRD) mapping, where the signal reflected by the FBG is first modulated by an RF signal and then sent to a dispersion compensation fiber (DCF). The OFRD can be acquired by measuring the slope change of the phase response of the DCF. Thanks to the sub-picosecond resolution OFRD measurement of the phase-derived ranging, the FBG demodulation resolution would be very high. The integer ambiguity, which is the primary limitation for large measurement range, is removed by sweeping the frequency of the RF signal in a certain range. In addition, the relative slope change of the phase response can be obtained using a larger frequency sweep interval compared to the traditional phase-derived ranging method, leading to a significant reduction of the measurement time. An experiment is performed, which applies the system to measure the temperature. A measurement range of more than 300 °C (corresponding to a wavelength shift of 3 nm) and measurement precision of ± 0.2 °C (corresponding to a wavelength shift of 2 pm) are achieved with a measurement speed of 20 ms.

中文翻译：

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基于光纤相对延迟测量的具有增强性能的 FBG 解调

基于微波光子学 (MWP) 的光纤布拉格光栅 (FBG) 解调具有高分辨率，但测量范围通常有限。在这里，我们提出了一种基于波长到光纤相对延迟 (OFRD) 映射的 FBG 解调系统，其中 FBG 反射的信号首先由 RF 信号调制，然后发送到色散补偿光纤 (DCF)。OFRD 可以通过测量 DCF 相位响应的斜率变化来获得。由于相位衍生测距的亚皮秒分辨率 OFRD 测量，FBG 解调分辨率将非常高。整数模糊度是大测量范围的主要限制，通过在一定范围内扫描射频信号的频率来消除。此外，与传统的相位衍生测距方法相比，可以使用更大的频率扫描间隔获得相位响应的相对斜率变化，从而显着减少测量时间。进行了一个实验，该实验应用该系统来测量温度。以20ms的测量速度实现超过300°C的测量范围（对应于3nm的波长漂移）和±0.2°C的测量精度（对应于2pm的波长漂移）。