利用倾斜光纤光栅的可开关双波长光纤激光器

报导了一种在四波混频作用下利用倾斜光纤布拉格光栅进行波长选择的可开关双波长掺铒光纤激光器。通过将倾斜光纤光栅与单模光纤进行横向错位焊接,使光栅的反向LP01和LP11两个模式具有相近的有效反射率,从而可以用来进行激光器的双波长选择。接入腔内的一段高非线性光子晶体光纤引入的四波混频效应克服了模式竞争,使得双波长激光在室温下稳定振荡。腔内起偏器和偏振控制器的联合作用可产生依赖于波长的损耗,以补偿光纤光栅两反射峰峰值的大小差异。基于以上原理,通过调节腔内的偏振态,该激光器实现了室温下稳定的双波长输出,也实现了在两波长之间的转换。两波长激光均有超过45 dB的信噪比,最大的功率波动为0.8 dB     

基于高双折射光纤布拉格光栅的自动增益控制掺铒光纤放大器

掺铒光纤非均匀展宽引起的空间烧孔现象导致单波长激光并不能完全控制放大器增益,提出了一种新颖的自动增益控制掺铒光纤放大器的结构:即采用高双折射光纤布拉格光栅产生抽运光,其写制光栅的波峰对应的波长分别为1549.3 nm和1549.83 nm,波长间隔为0.53 nm。通过调整偏振控制器,就实现了单激光或双激光的增益控制。这种设计增益控制范围为40 nm(1530~1570 nm),当输入功率在-40~-15 dBm的动态范围内,双激光增益控制的掺铒光纤放大器的平均增益和噪声系数分别约为22.22 dB和8.69 dB,而它们的漂移分别被钳制在0.69 dB和1.51 dB。系统性能测试表明:双激光控制掺饵光纤放大器在稳定性方面比单激光有着明显的优势。     

光纤光栅多点传感的理论与实验研究

对光纤布拉格光栅多点传感进行了理论研究与实验研究。通过定义多点传感信号分辨因子,分析了探测器对传感信号的分辨条件,给出了多点温度与应变传感原理的数学表达式,并探讨了由光源带宽决定的系统实际复用能力。设计并实现了具有一定特色的光纤布拉格光栅多点传感网络系统,利用该系统对温度、位移进行了双路、多点传感实验分析与理论验证,实验结果与多点传感理论分析相符合。     

基于高非线性光子晶体光纤Sagnac环形镜的全光开关

设计了一种新颖的、低开关功率的全光开关. 将高非线性光子晶体光纤和双向抽运掺饵光纤放大器引入Sagnac环形镜内，破坏了环形镜的对称性，利用交叉相位调制作用使反向传输的两路信号光产生非线性相移，从而实现开关效应. 理论分析表明：开关功率与放大器的增益倍数和光子晶体光纤非线性系数的积成反比，在实验中所得开关功率约40 mW，消光比约为15.9 dB，并且信号光透过率随脉冲控制光峰值功率呈余弦变化，实验结果与理论分析相吻合. 关键词： 全光开关 高非线性光子晶体光纤 环形镜 交叉相位调制     

Switchable Dual－Wavelength Mode－Locked Er－Doped Fibre Laser Using a Bragg Grating in Polarization－Maintaining Fibre

A simple actively mode-locked fibre ring laser is proposed and successfully demonstrated to generate switchable dual-wavelength picosecond pulses using a Bragg grating in a polarization-maintaining fibre. The wavelength spacing specified by the grating is only 0.52nm. The proposed laser can be made to operate in stable dualwavelength or switch between wavelengths at room temperature, only by simple adjustment of a polarization controller.     

A Novel Bi-wavelength Method for Accurately Measuring Gain and Noise Characteristics of an Erbium-Doped Fibre Amplifier for Multi-Channel Wavelength Division Multiplexing Transmission

Gain and noise figure (NF) are the most important two parameters of an erbium-doped fibre amplifier (EDFA) for a multi-channel wavelength division multiplexing (WDM) transmission system. A simple bi-wavelength method for accurate gain and NF spectrum measurement of EDFA for WDM applications is proposed. A saturating input signal, whose power equals to the sum of all the WDM signal power and whose wavelength is determined by the channel numbers and the wavelength of the WDM input signals, saturates the EDFA in a degree as the same as the WDM signals input. Meanwhile, a small power probe signal scans and measures the gain and the NF value at every wavelength of the WDM input signals. Investigative results by numerical simulation show that the gain and the NF spectra measured by this method have good agreement with the real spectra of the WDM signal input in a large total input power range. The maximum errors of the gain and the NF are less than 0.2 dB and 0.16dB, respectively, for a 50-channel input case. The method is competent for the accurate gain and the NF spectrum measurement of the fibre preamplifier and the line-amplifier for WDM applications and has the advantages of simplicity, convenience and easy implement.     

带隙型光子晶体光纤的泄露谱分析

利用光束传播法对带隙型光子晶体光纤（photonic crystal fiber, PCF）的泄露谱进行了数值分析.结果表明：PCF泄露谱往往具有多个带隙;泄露谱对PCF结构的变化异常敏感,泄露峰值波长和带隙波长不但与空气孔周期有关,还受空气孔直径的影响;由于PCF的空气孔内可填充液晶,泄露特性对液晶折射率的变化极其敏感,当液晶折射率增大时,峰值泄露波长和带隙波长都向长波漂移.     

联合变换相关器在光纤检测中离焦影响的讨论

对联合变换相关器在光纤检测中离焦采集谱问题进行了理论分析,计算机模拟以及光纤缺陷检测实验。得出了离焦距离与相关峰值的关系曲线,示出了对不同相似程度的输入物的离焦谱和焦面谱两种情况下进行相关的计算机模拟结果;提供了在焦面上和离焦一定范围两种情况下缺陷程度不同的光纤的相关检测结果。     

Simulations of Effect of High-Index Materials on Highly Birefringent Photonic Crystal Fibres

Novel highly birefringent photonic bandgap fibres （PBGFs） are obtained by filling of a high index material in the air holes of total internal reflection birefringent photonic crystal fibres. The effect of the filling high index material on the transmission characteristics has been theoretically investigated. The photonic bandgap has been achieved by using plane-wave method. Moreover, the phase and group modal birefringence have been studied by a full-vector finite-element method. Numerical results show that very high group and phase modal birefringence with magnitude of order of 10^-2 and 10^-3 has been respectively acquired, which is much higher than those of the non-filled fibres. Furthermore, strong coupling between surface modes and the fundamental modes has been found in the bandgap of the birefringent PBGFs, whose effect on the birefringence and confinement loss has also been discussed.     

Polarization-Independent All-Fibre Comb Filter with Dynamically Halved Channel Spacing

A polarization-independent all-fibre comb filter with dynamically halved channel spacing is proposed. The filter is based on high-birefringent fibre Sagnac interferometers and its channel spacing can be dynamically halved by turning on an optical switch. A good agreement between the numerical simulation and the experimental results is achieved.