基于激光外调制的频率可调谐光电振荡器

为了实现光电振荡器(OEO)输出频率的可调谐,提出了一种基于外调制激光的频率可调谐光电振荡器。此方案在单环OEO的基础上增加一个由微波滤波器、电衰减器、电放大器和电移相器构成的电增益选频腔,通过调节电移相器的偏置电压可以等效改变电选频腔的腔长,从而改变其输出微波信号的频率；同时调节光延时线来改变光电振荡器的起振模式,通过电增益选频腔信号与光电振荡器自由振荡信号的电注入锁定,即可实现频率可调谐的光电振荡器,其输出信号的频率由锁定OEO模式的电增益选频腔决定。实验结果表明,本方案产生了频率调谐范围为10.05 GHz~10.09 GHz、调谐步长为400 kHz的输出信号,频率在40 MHz的范围内连续可调谐。在输出频率为10.0519 GHz时,其边模抑制比为60 dB,相位噪声为-115 dBc/Hz @10 kHz。该方案结构简单,既保留了单环OEO低相位噪声的优势,又能有效抑制边模,为实现频率可调谐OEO提供了一种新的方法。

A tunable optoelectronic oscillator based on laser external modulation

In order to alter the output frequency of optoelectronic oscillator (OEO),a kind of tunable OEO based on laser external modulation is demonstrated. In this scheme,an electrical amplifying selective-frequency cavity composed of microwave filter,electrical attenuator,and electrical phase shifter and so on is added to the single-loop OEO. It generates tunable output RF signal by adjusting the bias voltage of electrical phase shifter,which equals to changing the length of electrical selective-frequency cavity. In addition,the oscillation mode of OEO can be changed by adjusting the optical delay line (ODL). The tunable OEO can be established by electrically injection locking between the output signal of selective-frequency cavity and the free oscillation signal of OEO,whose output frequency is determined by the selective-frequency cavity locking the corresponding oscillation mode of OEO. The experimental results show that the output signal with the frequency tuning range of 10.05 GHz~10.09 GHz,which is equivalent to 40 MHz,and the tuning step of 417 kHz is obtained. Its side mode suppression ratio is 60 dB when the output frequency is 10.0519 GHz,and the phase noise is -115 dBc/Hz @10 kHz. With a simple structure,this scheme not only preserves the advantage of low phase noise as OEO,but also effectively suppresses the side mode,which provides a new implementation method for tunable OEO.