Jiang Fan, Wong Jia Haur, Lam Huy Quoc, Zhou Junqiang, Aditya Sheel, Lim Peng Huei, Lee Kenneth Eng Kian, Shum Perry Ping, Zhang Xinliang
Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China.
Opt Express. 2013 Jul 15;21(14):16381-9. doi: 10.1364/OE.21.016381.
An optoelectronic oscillator (OEO) with wideband frequency tunability and stable output based on a bandpass microwave photonic filter (MPF) has been proposed and experimentally demonstrated. Realized by cascading a finite impulse response (FIR) filter and an infinite impulse response (IIR) filter together, the tunable bandpass MPF successfully replaces the narrowband electrical bandpass filter in a conventional single-loop OEO and serves as the oscillating frequency selector. The FIR filter is based on a tunable multi-wavelength laser and dispersion compensation fiber (DCF) while the IIR filter is simply based on an optical loop. Utilizing a long length of DCF as the dispersion medium for the FIR filter also provides a long delay line for the OEO feedback cavity and as a result, optical tuning over a wide frequency range can be achieved without sacrificing the quality of the generated signal. By tuning the wavelength spacing of the multi-wavelength laser, the oscillation frequency can be tuned from 6.88 GHz to 12.79 GHz with an average step-size of 0.128 GHz. The maximum frequency drift of the generated 10 GHz signal is observed to be 1.923 kHz over 1 hour and its phase noise reaches the -112 dBc/Hz limit of our measuring equipment at 10 kHz offset frequency.
提出并通过实验证明了一种基于带通微波光子滤波器（MPF）的具有宽带频率可调性和稳定输出的光电振荡器（OEO）。通过将有限脉冲响应（FIR）滤波器和无限脉冲响应（IIR）滤波器级联实现，可调带通MPF成功取代了传统单环OEO中的窄带电带通滤波器，并用作振荡频率选择器。FIR滤波器基于可调谐多波长激光器和色散补偿光纤（DCF），而IIR滤波器仅基于光学环路。利用长长度的DCF作为FIR滤波器的色散介质，也为OEO反馈腔提供了长延迟线，因此，可以在不牺牲生成信号质量的情况下实现宽频率范围内的光学调谐。通过调整多波长激光器的波长间隔，振荡频率可以从6.88 GHz调谐到12.79 GHz，平均步长为0.128 GHz。观察到生成的10 GHz信号在1小时内的最大频率漂移为1.923 kHz，并且在10 kHz偏移频率下其相位噪声达到我们测量设备的-112 dBc/Hz极限。
