复合滤波结构的窄线宽高频微波信号产生装置

为了在较低泵浦功率下实现单纵模双波长激光信号的输出，进而获得窄线宽的高频微波信号，设计并实验了一种基于复合滤波结构的窄线宽高频微波信号产生装置。通过8字腔结构布里渊增益腔和反射式光纤光栅构成的波长选择滤波器实现了4倍布里渊频移间隔的双波长斯托克斯光信号输出，采用200 m长单模光纤作为增益介质，同时与50 m长单模光纤构成级联光纤环结构，采用三端口耦合器与2 m长未泵浦的保偏掺铒光纤构成萨格纳克环结构，利用级联光纤环结构和萨格纳克环结构的复合滤波作用实现了斯托克斯光信号模式的选择，使输出的斯托克斯光信号由多纵模运行状态变为单纵模运行状态。实验证明:通过对输出的单纵模双波长斯托克斯光信号进行拍频检测可得42.85 GHz的高频微波信号产生，线宽为38 kHz；通过改变可调谐泵浦激光器的输出波长，可实现42.25~43.51 GHz范围内的频率调谐；通过稳定性测试，产生的42.85 GHz高频微波信号的频率变化在0.83 MHz内，峰值功率变化在±0.8 dB内，稳定性良好，满足实际应用需求。

Narrow linewidth high frequency microwave signal generator based on composite filter structure

In order to realize the output of single longitudinal mode dual-wavelength laser signal at lower pump power and obtain the high frequency microwave signal with narrow line width, the narrow linewidth high frequency microwave signal generator based on multiple filter compound structure was proposed and demonstrated. The dual-wavelength Stokes optical signal with four times Brillouin frequency shift interval was realized through the eight shaped Brillouin cavity structure and the wavelength selective filter composed by reflective fiber grating. The 200 m length single mode fiber was used as gain medium, and it forms a cascaded fiber ring structure with 50 m long single-mode fiber. A three-port coupler and 2 m long unpumped polarization-maintaining erbium-doped fiber was used to form a Sagnac ring structure. The cascaded fiber ring configuration and Sagnac ring configuration were designed to select mode for single longitudinal mode Stokes optical signal. The experiment proves that the high-frequency microwave signal of 42.85 GHz can be generated by the beat frequency detection of the output single-longitudinal-mode dual-wavelength Stokes optical signal, and the line width is 38 kHz; Changing the output wavelength of the tunable pump laser, frequency tuning in the range of 42.25-43.51 GHz can be achieved; Through the stability test, the frequency change of the 42.85 GHz high-frequency microwave signal is in the range of 0.83 MHz, and the peak power change is in the range of ±0.8 dB. It has good stability and meets the actual application requirements.