In this paper, a continuously tunable microwave photonic filter (MPF) with optical frequency comb (OFC) generated by recirculating frequency shifter (RFS) based on an inphase/quadrature (I/Q) modulator is proposed and experimentally demonstrated. A chirped fiber Bragg grating (CFBG) is inserted into the RFS loop to act as an optical bandpass filter. The central frequencies of two passbands of the MPF in 20 GHz range have been tuned linearly from 7.67 GHz to 9.04 GHz, and 15.34 GHz to 18.03 GHz, respectively by changing the frequency of the driving microwave signal onto the I/Q modulator from 20 GHz to 17 GHz. When the frequency of the driving microwave signal is decreased, OFC with smaller tone spacing is generated, and then the MPF's passbands move to higher frequency. So that, the proposed MPF's passbands with high frequencies can be achieved by applying driving microwave signal with low frequency to generate the OFC. By varying the bandwidth of the CFBG, the number of comb lines can be changed, which results in different bandwidth of the MPF's passband. Furthermore, in our experiment by carefully adjusting bias voltage of the Mach-Zenhder modulator, when the frequencies of driving microwave signal onto the I/Q modulator is 20 GHz and 18 GHz, one passband in the 20 GHz range can be suppressed at the frequency of 15.34 GHz, and 8.52 GHz, respectively.

中文翻译：

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循环移频器产生光频率梳的微波光子滤波器

提出并通过基于同相/正交（I / Q）调制器的循环移频器（RFS）生成带有光频率梳（OFC）的连续可调微波光子滤波器（MPF），并进行了实验验证。fiber光纤布拉格光栅（CFBG）插入RFS环路中，以用作光学带通滤波器。通过将驱动微波信号的频率从20 GHz更改为20 GHz，MPF的两个通带的中心频率分别在7.67 GHz至9.04 GHz和15.34 GHz至18.03 GHz处进行了线性调谐。至17 GHz。当降低驱动微波信号的频率时，会生成音调间隔较小的OFC，然后MPF的通带会移至更高的频率。因此，建议的强积金' 通过施加低频驱动微波信号以产生OFC，可以实现高频通带。通过改变CFBG的带宽，可以改变梳状线的数量，从而导致MPF通带的带宽不同。此外，在我们的实验中，通过仔细调整Mach-Zenhder调制器的偏置电压，当将微波信号驱动到I / Q调制器上的频率为20 GHz和18 GHz时，可以在该频率上抑制20 GHz范围内的一个通带。分别为15.34 GHz和8.52 GHz