基于半导体光放大器四波混频效应的多种调制格式的波长转换实验

实验报道了利用半导体光放大器(SOA)的四波混频(FWM)效应实现多种码型的波长转换.其中对于非归零(NRZ)信号实现了从单信道到三信道的多波长转换.调制速率从10 Gb/s到40 Gb/s均实现多波长转换.对于归零(RZ)信号分别实现了20 Gb/s和40 Gb/s的RZ格式的波长转换和40 Gb/s的载波抑制归零(CSRZ)格式的波长转换,利用光纤布拉格光栅(FBG)作为带陷滤波器消除共轭光和抽运光之间的串扰.对于非归零差分相移键控(NRZ_DPSK)信号分别实现了20 Gb/s和40 Gb/s的波长转换,利用实验室自制的光纤延时干涉仪进行NRZ-DPSK信号的解调.基于FWM效应的转换光的输出消光比大于7 dB,转换后消光比退化约为3 dB.     

High-Order Ultrawideband Pulse Generation from NRZ-DPSK Signals

A simple method to generate ultrawideband （UWB） doublet and triplet from nonreturn-to-zero （NRZ） differential phase shift keying （DPSK） signals is proposed and experimentally demonstrated. The proposed configuration consists of a Mach-Zehnder modulator （MZM） to generate NRZ-DPSK signals, a section of single-mode fibre to form a microwave bandpass filter, which is used to generate doublet pulses, and a Gaussian optical bandpass filter （OBF）, which serves as a frequency discriminator to generate higher-order UWB pulses. A pair of polarity- reversed triplet pulses is achieved by locating the optical carrier at the positive and negative linear Mopes of the OBF, where the OBF detuning is 0.12nm and -0.2 nm, respectively. The spectra of the pair of UWB triplets have a central frequency of 5 GHz and 5.6 GHz, and have a -10 dB bandwidth of 6.9 GHz and 8.1 GHz, respectively. The UWB pulses remain doublet shape when the light wavelength is located at the peak of the OBF. The spectrum of the doublet has a central frequency of 5.6 GHz and a -10 dB bandwidth of 6.9 GHz.     

光纤参变放大器光纤长度的优化设计

随着高输出功率掺铒光纤放大器和高非线性光纤的出现和使用,光纤参变放大器(OPAs)中出现了越来越多的增益饱和现象,这是光放大器中应该尽量避免的。对此,提出了依据光纤参变放大器的光纤非线性系数、抽运光功率、信号输入功率等参量对光纤长度进行优化设计的解决思路。明确提出最佳光纤长度的概念,即在其他参量一定的情况下使信号增益或信号输出功率达到最大所需的最小光纤长度,而且最佳光纤长度有利于提高光纤参变放大的增益带宽和波长转换带宽。通过数值积分求解描述光纤参变放大过程的非线性耦合方程,并运用控制变量法深入研究了最佳光纤长度与光纤非线性系数、抽运光功率、信号输入功率的关系。最后用最小二乘法进行数据拟合确定系数,得到简洁、实用的最佳光纤长度解析表达式。与已有实验结果比较表明,该解析式可很好地用来计算和优化光纤参变放大的光纤长度。     

A Proposal and Demonstration for Photonic Generation of a Microwave Signal by Incorporating a Microring Resonator

A proposal for photonic generation of a microwave signal is presented by employing a dual wavelength erbiumdoped fibre ring laser. In the laser, a microring resonator is cascaded with a tunable bandpass filter to serve as a dual-wavelength selector, an unpumped polarization maintaining erbium-doped fibre is used as a saturable absorber. By replacing the microring resonator with a delay interferometer to verify the proposal, a wavelengthtunable dual wavelength single longitudinal mode laser is demonstrated, and a microwave signal at 10.01 GHz with a linewidth of less than 25 kHz is obtained by beating the two wavelengths at a photodetector.     

Suppression of Nonlinear Patterning Effect in Wavelength Conversion Based on Transient Cross-Phase Modulation in Semiconductor Optical Amplifier Assisted with a Detuning Filter

Nonlinear patterning （NLP） effect in wavelength conversion based on transient cross-phase modulation （XPM） in semiconductor optical amplifier （SOA） assisted with a detuning filter is theoretically investigated. A non- adiabatic model is used to estimate the ultrafast dynamics of gain, phase and electron temperature in the SOA. Simulation results show that the NLP can be greatly suppressed by introducing an assist light, especially for the probe wavelength distant from gain peak. Furthermore, the results also indicate that the improvement is more evident for long wavelength probe light and assist light in counter-propagating configuration.     

基于折叠式超快非线性干涉仪的全光码型转换理论和实验研究

码型转换是实现非归零(NRZ)信号全光时钟恢复的关键技术.提出了一种基于折叠式超快非线性干涉仪的全光NRZ到伪归零(PRZ)信号转换的新型方案.基于半导体光放大器的分段模型和超快非线性干涉仪的传输函数，建立了该方案的理论分析模型，数值模拟了不同速率下的码型转换过程.实验实现了稳定的10，20和40 Gbit/s的NRZ到PRZ信号的码型转换，分析了影响码型转换输出特性的因素，理论分析结果与实验结果基本符合. 关键词： 超快非线性干涉仪 半导体光放大器 全光码型转换     

基于全矢量模式匹配法的三维弯曲波导本征模式计算

采用精确、严格的全矢量模式匹配法，计算了三维脊型弯曲波导和条形弯曲波导的本征模式，分析了模式折射率和辐射损耗随弯曲半径的变化关系.计算结果与已报道的有限差分法的结果符合很好.对文献中已报道但没有深入分析的现象给出了合理的解释.半径为50和12 μm的条形波导的计算结果表明：当波导的弯曲半径减小时，发生在分界面处的TE-TM模耦合会显著增强，这将导致弯曲波导中的模式不再是传统意义上的准TE模和准TM模，而是混合模.随着半径的减小，混合模的横向分量之间的差异会减小，当两个横向分量达到近似相等的强度时，波导的偏振相关性将会大大减小. 关键词： 导波光学 全矢量模式匹配法 微环谐振腔 光波导理论     

基于半导体光纤环形腔激光器的新型全光AND门和NOR门

提出了一种新型的基于半导体光纤环形腔激光器(SFRL)中同时发生的四波混频效应和交叉增益调制效应同时实现全光AND门和NOR门方案，并建立了这种全光逻辑门完整的宽带理论模型.通过数值模拟的方法，研究了输入信号光峰值功率及SFRL中两个耦合器的耦合比对这种全光逻辑门输出特性的影响. 关键词： 半导体光纤环形腔激光器 全光逻辑门 四波混频 交叉增益调制     

基于半导体光放大器的非归零信号时钟恢复

提出了一种基于半导体光放大器加窄带光纤光栅滤波器，将非归零信号转换为伪归零信号，再把伪归零信号注入到主动锁模环行腔激光器进行时钟提取的非归零信号时钟恢复方案.利用该方案实现了10 Gb/s伪随机非归零信号的全光时钟恢复，对工作原理和结果进行了分析和讨论.实验证明该方案具有结构简单，调整容易，输出波形好的特点.