Tunable frequency-multiplying optoelectronic oscillator based on a dual-parallel Mach-Zehnder modulator incorporating a phase-shifted fiber Bragg grating

A tunable frequency-multiplying optoelectronic oscillator (OEO) based on a dual-parallel Mach-Zehnder modulator (DPMZM) is proposed and experimentally demonstrated. In the proposed system, the tunable fundamental microware signal is generated by a tunable optoelectronic oscillator incorporating a phase-shifted fiber Bragg grating (PS-FBG). By adjusting the DC bias of the DPMZM, the frequency-doubled microwave signal with a tunable frequency range from 11 GHz to 20 GHz and the frequency-quadrupled microwave signal with a tunable frequency range from 22.5 GHz to 26 GHz are generated. The phase noises of the fundamental, frequency-doubled and frequency-quadrupled signals at 10 kHz offset frequency are ?105.9 dBc/Hz, ?103.3 dBc/Hz and ?86.2 dBc/Hz, respectively.     

多芯超模光纤放大器增益均衡设计(内封底文章)

多芯超模光纤(MCSMF)的芯间距较小,多个芯子共同形成芯区支持多个超模传输,与普通单芯少模光纤相比,其具有较大的有效模场面积和较小的模式串扰,备受关注。MCSMF用于长距离传输时,与其相匹配的新型增益均衡放大器是实现信号中继并保持信号稳定传输的必要器件。文中提出了一种基于粒子群优化算法的19芯超模光纤增益均衡放大器,该光纤支持10个超模共同传输。通过粒子群算法分别优化各纤芯内掺铒浓度来降低不同超模的交叠积分因子,从而减小模式增益差(DMG)。结果表明,在包层泵浦条件下,最大DMG从1.33 dB (各纤芯均匀掺杂)降低至0.20 dB,在1 550 nm信号波长处10模式的平均增益为27.79 dB,且该放大器在整个C波段的增益平坦度低于1 dB。     

光源带宽对基于光纤色散的光学相关器影响的研究EI北大核心CSCD

随着光通信系统传输速率的提高,尤其是光分组交换网络的使用,光的相关检测技术将在未来的通信领域(包括IP路由等)中发挥越来越重要的作用。从基于光纤色散的光学相关器基本原理出发,采用理论分析和数值仿真两种方法比较了不同带宽光源对光学相关器性能的影响,分析了光源随机相位噪声向幅度噪声转化的问题,得到了幅度噪声与光源带宽的关系,以及光源带宽不同时光学相关器输出的信噪比变化。根据仿真结果得到,基于非相干光源的光学相关器,能对速率为10Gb/s的8位和16位码元数据流进行高速相关检测,而32位的码元数据流仅能采用相干光源进行检测。此外,还对非相干光源在模拟信号的相关检测中的应用进行了探讨。     

多层光纤布拉格光栅的理论与实验研究

从理论和实验两方面研究了在非周期性多层光纤上写入布拉格光栅的光学特性。从耦合模理论出发,讨论了光纤具有多于一个光敏层的情况。在实验室自制的两类多层光纤上写入光栅的实验也表明,该类光栅具备有一般光栅的普遍光学特性,说明在使用多层光纤作为关键部分构建器件时,需要的各类光栅部件能够通过直接在该类光纤上写入光栅实现。紫外光在氢载掺铒多层光纤上写入光栅的实验说明分层的异种元素掺杂将导致芯区应力增加,从而辅助提高光纤的光敏性。     

Optical ultra-wideband pulse generation and distribution using a dual-electrode Mach-Zehnder modulator

<正>A novel approach to generate and distribute ultra-wideband(UWB) pulses in optical domain is investigated. In this proposed scheme,a dual-electrode Mach-Zehnder modulator(DE-MZM) is biased at its quadrature point so as to realize the linear response.Then the intensity of output optical field can be assumed to the subtraction of two input Gaussian pulses.If the input Gaussian pulses are with the same sharp parameters but different time delays,a quasi-monocycle-waveform UWB signal can be generated.If the input Gaussian pulses are with different amplitudes and full-width at half-maximum(FWHM),a quasi-doublet-waveform UWB signal can be generated.A transmission of the UWB signals through a 25-km single mode fiber is carried out successfully.The results in both temporal and frequency domains are also presented.     

偏振器件在通信和传感中的应用

偏振器件是光纤通信和光纤传感系统中的重要器件.随着光纤光学的发展,偏振器件的应用越来越广泛,并且开发出了许多新的类型.为此总结了偏振器件在光纤通信及光纤传感领域中的应用,并对偏振器件的研究方向作了展望.     

Spectral characterization of fiber Bragg grating with etched fiber cladding

A new method is presented to tune Bragg wavelength slightly by using hydrofluoric acid to etch fiber cladding.The spectral characteristics before and after etching and the change properties of Bragg wavelength are studied.Cladding modes are reduced during the etching process.High-order cladding modes are converted into radiation modes,and energy of cladding modes is coupled to the outside.As the cladding radius decreases,the Bragg wavelength shifts to longer direction.Experimental results show that this method can tune Bragg wavelength slightly,and the tunable range is 0.002-0.120 nm.     

基于光纤光栅及EDA技术的新型大范围高灵敏度测重仪

利用光纤光栅中心反射波长受应力变化的特性,结合已有的EDA(电子设计自动化)技术,构建了一个新型大范围、高灵敏度的测重系统.利用光纤光栅及环行器构建了一个温度不敏感的高灵敏度的测重探头,通过不同型号光栅实现了几克到几千克大范围测重;利用光电探测器及CPLD芯片,将nW级的光信号转化为电信号进行处理,最终通过对逻辑器件编程,还原出重力.通过实验数据对系统的理论进行了检验,取得了良好的效果.     

基于二次外差法的八倍频毫米波光子发生器特性

研究了一种基于二次外差法的八倍频毫米波光子发生器.该方案将二次外差法的相关原理应用到倍频式毫米波光子发生器的研究中.利用两次拍频,抵消两个独立激光器各自的相位噪声,得到了频率八倍于射频本振频率的射频毫米波信号.理论推导了毫米波产生的原理,讨论了影响射频功率代价的激光器相位噪声、光纤色散和光链路的延时失配问题,在此基础上进行了仿真模拟验证了光子发生器的工作原理及在模拟光链路中的应用.     

Experimental research of temperature sensor based on twin-core fiber

A low-cost, compact, and lossless temperature sensor based on a twin-core fiber (TCF) is demonstrated and manufactured by splicing two single-mode fibers to the ends of a TCF. The extinction ratio of the comb transmission spectrum is bigger than 15 dB, and the temperature sensitivity of the coupling angle is –0.02 rad/(°C· m) at–30–90°C and –0.032 rad/(°C· m) at 90–175°C. Finite element method is used to calculate the supermodes of the TCF, and the result agrees well with the experiment.