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A modal interferometer is experimentally demonstrated based on tapering a single-mode-multimode-singlemode (SMS) fiber structure heated by hydrogen flame.The interference fringe begins to form when tapering length is 19.8 mm,and becomes regular and clear when the tapering length is longer and the tapered waist diameter is smaller.Annealing process is undertaken to achieve a high extension ratio of approximately 17 dB with free spectral range of 1.5 nm when the tapering length is 33 mm and the tapered waist diameter is approximately 5μm.The temperature and axial strain dependences of the tapered SMS structure are characterized,and the measured temperature and strain coefficients are +7 pm/℃and -9.536 pm/με, respectively.  相似文献   
2.
We experimentally demonstrate the ultra-high range resolution of a photonics-based microwave radar using a high repetition rate actively mode-locked laser(AMLL). The transmitted signal and sampling clock in the radar originate from the same AMLL to achieve a large instantaneous bandwidth. A Ka band linearly frequency modulated signal with a bandwidth up to 8 GHz is successfully generated and processed with the electro-optical upconversion and direct photonic sampling. The minor lobe suppression(MLS) algorithm is adopted to enhance the dynamic range at a cost of the range resolution. Two-target discrimination with the MLS algorithm proves the range resolution reaches 2.8 cm. The AMLL-based microwave-photonics radar shows promising applications in high-resolution imaging radars having the features of high-frequency band and large bandwidth.  相似文献   
3.
This Letter demonstrates the effectiveness of a high-speed high-resolution photonic analog-to-digital converter(PADC) for wideband signal detection. The PADC system is seeded by a high-speed actively mode locked laser,and the sampling rate is multiplied via a time-wavelength interleaving scheme. According to the laboratory test,an X-band linear frequency modulation signal is detected and digitized by the PADC system. The channel mismatch effect in wideband signal detection is compensated via an algorithm based on a short-time Fourier transform. Consequently, the signal-to-distortion ratio(SDR) of the wideband signal detection is enhanced to the comparable SDR of the single-tone signal detection.  相似文献   
4.
This Letter investigates the impact of the photodiode(PD) saturation in a sub-sampled photonic analogto-digital converter(PADC) with two individual pulse lasers. It is essentially proved that when the optical power to the saturated PD increases, the optical–electrical conversion(OEC) responsivity and digitized output power of the PADC decrease. If femtosecond pulses are employed for the PADC sampling clock, the time-stretching process in a dispersive medium is necessary to decrease the impact of the PD saturation. In contrast, when the sampling clock with picosecond pulses is utilized, the PD saturation is more tolerable, and thus, the OEC responsivity can be improved by an increase of the optical power to the PD no matter if the time-stretching process is employed.  相似文献   
5.
We investigate a channel-interleaved photonic analog-to-digital conversion(PADC)system’s ability to work stably over a long duration with an optimal driving voltage.The influence of optimum bias point drift of a Mach–Zehnder modulator(MZM)-based photonic switch on this system was analyzed theoretically and experimentally.The feasibility of extracting feedback signals from the PADC system was derived.A high-stability channel-interleaved PADC was constructed by extracting a feedback signal from a parallel demultiplexing module to control the MZM-based photonic switch’s driving voltage.Consequently,the amplitude mismatch between the channels was limited to within 0.3 d B over 12 hours of operation.  相似文献   
6.
针对光纤偏振随机偏转的问题,提出了一种受激布里渊散射瞬时频率测量技术的优化方案。对比分析了单模光纤和保偏光纤用于实现受激布里渊散射瞬时频率测量的特性差异。实验结果表明:与单模光纤相比,保偏光纤中的偏振随机偏转现象得到有效抑制,测量系统的频率分辨率由225MHz提高至90MHz。  相似文献   
7.
提出一种基于互逆光纤色散的微波光子雷达系统设计方案,既可以产生宽带线性调频信号,又可以实现线性调频信号的光域脉冲压缩.在发射端利用互逆色散光纤产生线性调频信号.在接收端,雷达回波信号通过马赫-曾德调制器调制到预啁啾的光信号上,然后经过色散光纤的进一步色散.最终在探测器端可以得到目标回波信号脉冲压缩后的结果.该方案无需脉冲压缩过程中数字化和离线处理,且具有脉冲压缩比的调谐作用.理论、数值仿真和实验证明了该设计方案能有效进行线性调频信号的光域脉冲压缩.实验产生了C波段下时宽1.2ns,带宽3.2GHz的线性调频信号,并通过互逆色散光纤将该信号压缩到了0.09ns,脉冲压缩比达13.3.  相似文献   
8.
光子时间拉伸模数转换(PTS-ADC)系统利用光纤中的色散效应对被采样模拟信号进行时间拉伸和带宽压缩,可大幅提高电模数转换器(ADC)的采样率和带宽。现有的PTS-ADC系统需要很长的色散光纤作为传输介质,它所带来的损耗限制了系统信噪比(SNR)和有效比特位(ENOB)。虽可通过提高光脉冲功率来改善系统的SNR,但色散光纤中的非线性效应利用了信噪比的提升。从理论推导、数值仿真和实验验证三个方面综合分析了非线性效应对PTS-ADC系统性能的影响,包括系统功率传输函数、载波与谐波功率比(CIR)。结果表明:第一段色散光纤中的非线性效应不会使得被采样模拟信号失真,相反地会提高系统带宽和CIR;而第二段色散光纤中的非线性效应则会恶化系统性能,应予以避免。  相似文献   
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