布里渊双波长窄线宽光纤激光器及其扫频微波信号生成

Brillouin Dual-wavelength Narrow-linewidth Fiber Laser and Its Application in Frequency-swept Microwave-signal Generation

提出并验证了一种基于高非线性光纤(HNLF)的布里渊双波长窄线宽光纤激光器,并对其扫频微波信号生成进行了研究。窄线宽光纤激光种子源经高功率掺铒光纤放大器进行功率放大,并使用光纤光栅滤除自发辐射噪声后,作为受激布里渊散射(SBS)的泵浦光;为降低SBS阈值,使用长3.0 m的HNLF作为布里渊增益介质,布里渊激光谐振腔的腔长为6.6 m,对应的纵模间隔约为31 MHz,可以保证在布里渊增益谱范围内实现激光单纵模运行;在HNLF入纤泵浦光功率为1.8 W时,测得布里渊激光的线宽为622.50 Hz,且结合残余泵浦光得到了双波长激光输出,光信噪比>77 dB;对双波长激光进行拍频,在9.4 GHz附近得到微波信号,且利用定制步进电机光纤拉伸机构对HNLF引入应变调制,实现了速率为10 Hz、范围为289.7 MHz的扫频微波信号输出。提出的激光器系统实现方法简单,在光/无线通信、光纤传感、微波光子学等领域具有潜在应用价值。

A Brillouin dual-wavelength narrow-linewidth fiber laser with a high-nonlinear-fiber(HNLF)is proposed and demonstrated,and the frequency-swept microwave-signal generation with the fiber laser is studied in detail. A narrow-linewidth fiber laser source as the seed laser is amplified by a high-power erbium-doped fiber amplifier. The amplified laser is then filtered to remove the strong amplified spontaneous emission noise by a high-reflection fiber Bragg grating(FBG)with the reflecting center wavelength close to the seed fiber laser’s output wavelength,and is subsequently used as the pump laser of stimulated Brillouin scattering(SBS)of the HNLF. The length of HNLF is 3. 0 m long,which can provide a low SBS pump threshold. The cavity length of the Brillouin laser is 6. 6m,corresponding to a longitudinal-mode spacing of ~31 MHz,which can ensure the single-longitudinal-mode operation of the Brillouin laser. When the input power of HNLF is 1. 8 W,the linewidth of the Brillouin laser measured is 622. 50 Hz,and the dual-wavelength lasing output with a signal-tonoise ratio(OSNR)of >77 dB is obtained by combining the residual pump laser and the Brillouin laser. By beating the dual-wavelength laser output,a microwave signal with a frequency around 9. 4GHz is obtained. Using a step-motor based fiber stretcher to introduce strain modulation to the HNLF,the frequency-swept microwave signal with a sweep-range of 289. 7 MHz and a sweep-rate of 10Hz is realized. The proposed fiber laser has potential applications in optical/wireless communication,fiber sensing,and microwave photonics.