A continuously tunable multi-tap complex-coefficient microwave photonic filter based on a tilted fiber Bragg grating.
A continuously tunable multi-tap complex-coefficient microwave photonic filter based on a tilted fiber Bragg grating.
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DOI：
10.1364/oe.21.007521
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发表时间：
2013-03
期刊：
影响因子：
3.8
通讯作者：
H. Shahoei;J. Yao
中科院分区：
文献类型：
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作者：
H. Shahoei;J. Yao
倾斜光纤布拉格光栅（TFBG）包层模谐振耦合系数在不同波长范围内呈线性增加或减小。根据Kramers-Kronig关系，当耦合系数线性增加时，相移也相应线性增加。这一特点，首次采用的多抽头连续可调谐微波光子滤波器的实现与复杂的系数，通过使用TFBG。通过将单边带调制信号的光载波定位在具有线性增加的深度的TFBG的包层模式谐振处，将线性增加的相移引入到光载波。通过用单边带拍频光载波，相移被转换为微波信号，从而产生具有所需线性增加相移的复系数。通过对写入铒镱共掺光纤中的TFBG进行光抽运，实现了光纤复系数的可调谐性。进行了概念验证实验;分别演示了频率可调范围为150和120 MHz的三抽头和四抽头滤波器。
The coupling coefficients of the cladding-mode resonances of a tilted fiber Bragg grating (TFBG) are linearly increasing or decreasing in different wavelength regions. Based on the Kramers-Kronig relations, when the coupling coefficients are linearly increasing, the phase shifts are linearly increasing correspondingly. This feature is employed, for the first time, for the implementation of a multi-tap continuously tunable microwave photonic filter with complex coefficients by using a TFBG. By locating the optical carriers of single-sideband-modulated signals at the cladding-mode resonances of the TFBG which has linearly increasing depths, linearly increasing phase shifts are introduced to the optical carriers. By beating the optical carriers with the single sidebands, the phase shifts are translated to the microwave signals, and thus complex coefficients with the required linearly increasing phase shifts are generated. The tunability of the complex coefficients is realized by optically pumping the TFBG which is written in an erbium/ytterbium (Er/Yb) co-doped fiber. A proof-of-concept experiment is performed; a three- and four-tap filter with a frequency tunable range of 150 and 120 MHz, respectively, are demonstrated.