基于载波相移系统的二倍频光电振荡器

A frequency-doubling optoelectronic oscillator based on carrier phase-shifted system

为了扩展光电振荡器(OEO)的频率范围,设计了一种基于载波相移系统的二倍频OEO(FD-OEO)。系统采用相位调制器(PM)和Mach-Zehnder调制器(MZM)并联,构成载波相移系统,利用载波相移双边带(CPS-DSB)调制的方法产生二次谐波分量;同时利用啁啾光纤布拉格光栅(CFBG)色散特性实现边带分量与CPS补偿,维持OEO环路中基频信号的振荡。实验结果显示,在OEO环路系统基频信号为2.23GHz情况下,产生了4.30GHz的FD信号,且通过边模抑制性能、稳定性及相位噪声对系统性能进行了验证。

In order to extend the frequency range of optoelectronic oscillator （OEO）, a novel frequency- doubling optoelectronic oscillator （FD-OEO） based on carrier phase-shifted system is proposed and ex- perimentally demonstrated. In the proposed system, the phase modulator （PM） and a Mach-Zehnder modulator （MZM） operate in parallel,which implements a carrier phase-shifted double sideband （CPS- DSB） modulation to generate a microwave signal at the second-harmonic frequency via photodetector （PD）. Meanwhile,the chirped fiber Bragg grating （CFBG） ensures the oscillation of the fundamental frequency signal by rotating the phase between the optical sidebands and the carrier. The proposed OEO is experimentally demonstrated. A self-starting microwave signal at 2. 23 GHz and a frequency-doubling microwave signal at 4.30 GHz are simultaneously generated. Moreover, the phase noises and the long- term stability of the generated microwave signals are also investigated. The phase noises of the generated frequency-doubling microwave signal at 4. 30 GHz and the fundamental frequency microwave signal at 2. 23 GHz are - 101, 58 dBc/Hz at 100 kHz and -- 107.87 dBc/Hz at 100 kHz, respectively. The frequen- cy drift and the power drift are approximately 3 kHz and 1 dBm over 12 rain,respectively,and no signifi- cant mode hopping is observed over a longer period of time.