Opt Lett. 2018 Jun 1;43(11):2664-2667. doi: 10.1364/OL.43.002664.
A new fiber Bragg grating (FBG) wavelength shift demodulation method based on optical true time delay microwave phase detection is proposed. We used a microwave photonic link (MPL) to transport a radio frequency (RF) signal over a dispersion compensation fiber (DCF). The wavelength shift of the FBG will cause the time delay change of the optical carrier that propagates in an optical fiber with chromatic dispersion, which will result in the variation of the RF signal phase. A long DCF was adopted to enlarge the RF signal phase variation. An IQ mixer was used to measure the RF phase variation of the RF signal propagating in the MPL, and the wavelength shift of the FBG can be obtained by the measured RF signal phase variation. The experimental results showed that the wavelength shift measurement resolution is 2 pm when the group velocity dispersion of the DCF is 79.5 ps/nm and the frequency of the RF signal is 18 GHz. The demodulation time is as short as 0.1 ms. The measurement resolution can be improved simply by using a higher frequency of the RF signal and a longer DCF or larger chromatic dispersion value of the DCF.
提出了一种基于光学真延时微波相位检测的光纤布拉格光栅（FBG）波长移动解调新方法。我们利用微波光子链路（MPL）在色散补偿光纤（DCF）中传输射频（RF）信号。FBG 的波长移动会导致在具有色散的光纤中传播的光载波的延时变化，从而导致 RF 信号相位的变化。采用长的 DCF 来放大 RF 信号相位的变化。IQ 混频器用于测量在 MPL 中传播的 RF 信号的 RF 相位变化，并且可以通过测量的 RF 信号相位变化来获得 FBG 的波长移动。实验结果表明，当 DCF 的群速度色散为 79.5 ps/nm 且 RF 信号的频率为 18 GHz 时，波长移动测量分辨率为 2 pm。解调时间短至 0.1 ms。通过使用更高频率的 RF 信号和更长的 DCF 或更大的 DCF 色散光值，简单地提高测量分辨率。
