基于啁啾相移FBG的宽调谐单通带微波光子滤波器

为扩大单通带微波光子滤波器(MPF)的可调谐 范围,提出了一种基于啁啾相移光纤光栅(PS-FBG) 的宽调谐单通带MPF。首先对普通PS-FBG的反射谱和基于普通PS-FBG的单通带MPF频率响应 进行了理 论和实验研究;然后,采用传输矩阵方法分析了啁啾PS-FBG的相移量、折射率调制深度以 及相移点位置 对其反射谱特性的影响,进而分析了对基于啁啾PS-FBG的单通带MPF频率响应的影响。结果 表明,调节可调谐激光 源的波长,可实现单通带频率的可调;相对于普通PS-FBG,啁啾PS-FBG扩大了反射谱带宽 ,从而单通带MPF扩大了可调谐范围。适当设计啁啾PS-FBG的相移点的位置,可以使单通带M PF的可调谐范围进一步增加。     

基于双光源的可调谐微波光子滤波器

提出了一种基于双光源与双相移光纤光栅(DPS- FBG)的可调谐微波光子滤波器。双光源经过相 位调制后,利用DPS-FBG的反射模式中的两超窄陷波分别对两相位调制光信号的边带进行抑 制,实现相 位调制至强度调制的转换。通过调节两光源的中心波长可以实现单通带与双通带之间的切换 ,实现单通带 的中心频率可调以及3dB带宽可调,实现双通带频率同时可调或者单独可调。建立了理论模 型并进行了数 值分析,最后通过实验进行了验证。实现了滤波器通带的3dB带宽由180MHz增加为319MHz,中心频率从1GHz到7GHz可调。     

基于无限冲激响应的微波光子级联滤波器

为进一步拓展微波光子滤波器的 FSR(自由谱范围)和提高滤波器的Q值,进行了 IIR(无限冲激响应)滤波器分别与FIR(有限冲激响应)滤波器和 IIR滤波器级联的研究。分析了两种级联结构的滤波特性并给出了相应的传输函数。IIR滤波器与FIR滤波器级联后的FSR与Q值是IIR滤波器的2n倍;IIR滤波器与IIR滤波器级联后的FSR是各个IIR滤波器的FSR的最小公倍数。用 Matlab软件仿真验证了两种级联结构的频率响应特性,实验验证了 IIR滤波器与 IIR滤波器的级联特性。IIR滤波器与 IIR滤波器的级联有望实现宽频率范围内的单通带滤波器。     

A high-Q microwave photonic filter by using an SOA-based active mode-locked fiber ring laser

A high-Q microwave photonic filter using a semiconductor optical amplifier (SOA)-based mode-locking fiber ring laser is proposed, analyzed and experimentally demonstrated. The proposed microwave photonic filter can realize a high-Q frequency response, it is compact without an optical source, and it can be easily tuned by adjusting an optical variable delay line in a ring cavity. A result with a Q-factor of about 236 and a rejection ratio of about 45 dB is obtained. The measured results and the theoretical estimations agree very well.     

A cascaded microwave photonic filter based on a low-coherence infinite-impulse-response filter

A cascaded filter combining active and passive filters is proposed. The active filter acts as a low-coherence infinite-impulse-response (IIR) filter and achieves a sharp frequency response. The low-coherence IIR filter is realized by employing the cross-gain modulation (XGM) of the amplified spontaneous emission (ASE) spectrum of the semiconductor optical amplifier (SOA). The passive filter is an n-section unbalance Mach-Zehnder (UMZ) structure, which is used to increase free spectral range (FSR) and Q factor further. The low-coherence IIR filter cascaded with one section of UMZ passive filter is experimentally demonstrated, and a Q factor of 1268 is obtained.     

Instantaneous microwave frequency measurement based on hybrid microwave photonic filter

A novel photonic technique for instantaneous microwave frequency measurement based on hybrid microwave photonic filter （HMPF） is proposed and experimentally demonstrated. The HMPF is composed of an all-pass filter and a band-pass filter with negative coefficients. By properly controlling the power relationship between the all-pass filter and the band-pass filter, the HMPF can realize a monotonic frequency response, and then a unique relationship be- tween the output power and the input frequency is established. A high measurement resolution can be achieved for a given frequency range.