双折射色散阶跃光纤中拉曼效应和参量放大增益谱

在拉曼效应和参量放大共同作用下,当激光脉冲在双折射光纤中传输时,根据所遵循的耦合模方程,通过引入平行拉曼增益的洛伦兹模型,导出了当输入泵浦波偏振方向同双折射轴成45°角时,在双折射色散阶跃光纤中拉曼效应和参量放大共同作用所导致的增益,讨论并分析了在不同色散区增益谱随相关参量的变化。结果表明:由于拉曼效应、参量放大、双折射和色散的相互作用,导致增益谱的斯托克斯波与反斯托克斯波彼此不对称;在反常色散区,产生的增益以反斯托克斯波为主,在正常色散区则以斯托克斯波为主;当表征距离的级数m发生变化时,增益谱也随之发生变化,可以利用色散阶跃光纤在适当的级数m位置提取T频率脉冲。     

Polarization modulational instability in a birefringent optical fiber with fourth order dispersion

We obtain conditions for the occurrence of polarization modulational instability in the anomalous and normal dispersion regimes for the coupled nonlinear Schrödinger equation modelling fourth order dispersion effects when the linearly polarized pump is oriented at arbitrary angles with respect to the slow and fast axes of the birefringent fiber.     

双折射光纤中拉曼效应对参量放大增益谱的影响

根据激光脉冲在光纤中传输时, 所满足的波动方程, 导出了拉曼效应和参量放大共同作用下, 在双折射光纤中所遵循的耦合模方程, 并引入平行拉曼增益的洛伦兹模型, 给出了输入抽运波偏振方向同双折射轴成45^o 时, 拉曼效应和参量放大共同作用所导致的增益. 讨论并分析了拉曼效应在不同色散区对参量放大增益谱的影响. 结果表明, 在考虑拉曼效应后, 使得参量放大斯托克斯波与反斯托克斯波增益谱彼此不对称; 在反常色散区, 产生的增益以反斯托克斯波为主, 正常色散区则以斯托克斯波为主.     

Symmetry and degeneracy in microstructured optical fibers

The symmetry of an optical waveguide determines its modal degeneracies. A fiber with rotational symmetry of order higher than 2 has modes that either are nondegenerate and support the complete fiber symmetry or are twofold degenerate pairs of lower symmetry. The latter case applies to the fundamental modes of perfect microstructured optical fibers, guaranteeing that such fibers are not birefringent. We explore two numerical methods and demonstrate their agreement with these symmetry constraints.     

基于小圆孔结构纤芯的高双折射光子晶体光纤

为了实现高双折射光子晶体光纤,提出了一种在纤芯中引入微小圆孔的方法.利用全矢量有限元方法和完美匹配层条件研究了基于圆孔微细结构纤芯的光子晶体光纤的双折射特性.讨论了纤芯圆孔数量、孔径、间隔距离对光纤双折射特性的影响;设计了一种双折射达到10－2量级的光子晶体光纤.模拟结果表明采用三个以上圆孔可以获得较大的双折射,增大外包层数目可以有效减小约束损耗.     

Interference of white light in tandem configuration of birefringent crystal and sensing birefringent fiber

Spectral interference of white-light beams propagating through a tandem configuration of birefringent crystal and sensing birefringent fiber is analyzed theoretically and experimentally. The spectral interference law is expressed analytically under the condition of a Gaussian response function of a spectrometer taking into account the dispersion of birefringence in the crystal and in the fiber. Two types of spectral interferograms are modeled knowing dispersion characteristics of the sensing fiber and using a quartz crystal of the positive or a calcite crystal of the negative birefringence. The theoretical analysis is accompanied by two experiments employing a highly birefringent fiber and a birefringent quartz crystal of two suitable thicknesses. Within both experiments the spectral interference fringes are resolved in accordance with the theory with phases dependent on the fiber length.     

Birefringent azopolymer long period fiber gratings induced by 532 nm polarized laser

Based on the photoinduced birefringence in azo materials, the model of the birefringent long period fiber gratings (BLPFGs) has been proposed and the transmission of such birefringent fiber gratings was further simulated by the coupled mode theory. In order to obtain the optimum condition for making birefringent azopolymer optical fiber (APOF) gratings the photoinduced birefringence of azo dye and methyl methacrylate (MMA) copolymers was systematically studied. After photosensitivity study of azo samples, using Teflon technique, azo dye containing single mode polymer optical fiber (POF) was fabricated. Finally, BLPFGs can be fabricated in azopolymer fiber using polarized 532 nm laser. A 120 μm LPFG with a 50% duty cycle has been successfully written within the core of the fiber with 532 nm laser by an amplitude mask method. Under polarized microphotography, the grating was observed when the optical axis was set at 45° with the direction of the first polarizing lens of the polarization microscope.     

在保偏光纤上制作光纤光栅的应用研究

提出一种在保偏光纤上计算光纤拍长的方法，即在保偏光纤上制作光纤光栅，利用光纤光栅的特性可以方便地求得光纤的拍长，同时，发现在保偏光纤上写入光纤光栅，其过程等效于在两个主轴上分别写入了一个光纤光栅，并且这两个光栅对于光的偏振态具有选择性，它们分别作用的偏振态是相互正交的。利用此特性，可以得到偏振消光比比较高的偏振分束器。     

非线性双折射色散光纤中极化调制不稳定性分析

利用光脉冲在光纤中传播时所遵守的相干非线性薛定谔耦合方程,研究了线偏振光在光纤中的传输特性.结果表明:由于线性双折射、非线性效应和色散的相互作用,导致光的偏振状态发生变化,产生交叉相位调制(XPM),从而导致调制不稳定性.这一调制不稳性不仅在反常色散区产生,在正常色散区也能产生,并且线性双折射发生变化时,增益谱也随之发生变化.     

Higher-order Gabitov–Turitsyn equation for solitons in optical fibers

The higher-order multiple-scale asymptotic analysis is carried out for the Gabitov–Turitsyn equation that governs the propagation of dispersion-managed solitons through optical fibers. The averaged equation, with the consideration of higher-order terms, provides an in-depth understanding of the soliton propagation through an optical fiber. The polarization preserving fibers as well as birefringent fibers are considered in this paper. Finally, the study is extended to the case of multiple channels, namely dispersion-flattened fibers.     

Vector Breathers in an Averaged Dispersion-Managed Birefringent Fiber System

A variable-coefficient coupled nonlinear Schrodinger equation in an averaged dispersion-managed birefringent fiber is investigated. Based on the one-to-one correspondence between variable-coefficient and constant-coefficient equations, an analytical breather solution is derived. As an example to exhibit dynamical behaviors of solution, its controllable excitations including rear excitation, peak excitation and initial excitation are discussed.     

Up to 8-GHz Ultrafast Multi-Wavelength Routing Operation of Active Birefringent Fiber Loop Filter/Interleaver Using a Traveling-Wave-Type Phase Modulator

Ultrafast multi-wavelength routing by an active birefringent fiber loop filter/interleaver is proposed and demonstrated. In the proposed active filter, the loop part consists of a birefringent optical fiber and a traveling-wave-type phase modulator. Numerical simulation using Jones matrix analysis shows that the periodic transmission/reflection bands of the filter can be switched by changing a phase difference between clockwise and counter clockwise components passing through the birefringent fiber loop. Experimentally, we realize fast switching by controlling the applied voltage to the phase modulator, and 8-GHz wavelength routing operation is achieved.     

强双折射光纤中超短光脉冲压缩效应研究

研究了强双折射光纤中沿偏振主轴入射的超短光脉冲压缩效应。当考虑三阶色散效应时，三阶色散与光纤非线相互作用能增强一偏振光脉冲的压缩而抑制另一偏振光脉冲的压缩。正三阶和的强慢孤子压缩，负三阶色散增强快孤子压缩，三阶色散参量越大，脉冲压缩效果越明显。     

Vector Breathers in an Averaged Dispersion-Managed Birefringent Fiber System

A variable-coefficient coupled nonlinear Schrödinger equation in an averaged dispersion-managed birefringent fiber is investigated. Based on the one-to-one correspondence between variable-coefficient and constant-coefficient equations, an analytical breather solution is derived. As an example to exhibit dynamical behaviors of solution, its controllable excitations including rear excitation, peak excitation and initial excitation are discussed.     

Multiwavelength fiber laser based on a photonic crystal fiber loop mirror with cooperative Rayleigh scattering

In this work, a multiwavelength fiber Raman laser based on a highly birefringent photonic crystal fiber loop mirror is presented. A laser resonator is formed when the Raman amplification with cooperative Rayleigh scattering in a dispersion-compensating fiber is used as a distributed mirror and combined with a photonic crystal fiber loop mirror filtering structure. Stable multiwavelength lasing at room temperature is achieved due to the low temperature sensitivity of the highly birefringent photonic crystal fiber.     

Research on Reduction of PMD in Single Mode Fiber

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Fiber-optic interferometric point thermometer

A modulation technique suitable for short optical fiber interferometric sensors is presented. This is a passive technique that makes use of modal properties of highly birefringent fiber to generate quadrature output components. Experimental results are presented for 2 miniature, remote Fabry-Perot interferometers fabricated from 2 different types of highly birefringent fiber using this signal processing method.     

一种新型高双折射光子晶体光纤特性研究

设计了一种高双折射高非线性光子晶体光纤, 采用全矢量有限元法研究了这种光纤的基模模场、双折射、非线性、有效模面积及色散特性. 数值研究发现, 减小孔间距Λ的大小, 在波长1550 nm 处, 该光纤可获得10^-2 数量级的双折射B, 比普通的椭圆保偏光纤高约两个数量级; 同时, 该光纤可获得42 W^-1·km^-1 的高非线性系数γ. 另外,分别在可见光和近红外波段出现了两个零色散波长, 在波长800–2000 nm 之间具有良好的色散平坦特性. 这种设计为获得高双折射高非线性超平坦色散光子晶体光纤提供了一种新的方法, 该光纤在偏振控制、非线性光学和色散控制方面具有广泛的应用前景. 关键词： 光子晶体光纤 高双折射 高非线性 有限元法     

磁场中双折射光纤的琼斯矩阵等效模型

采用延迟器与旋光器的串联模型, 研究磁场中双折射光纤的偏振传输特性, 将它们的琼斯矩阵按照两种不同的顺序级联相乘, 导出了两种等效模型中等效相位延迟量、等效快轴方向和等效旋光角的解析表达式。研究发现, 当光纤同时具有线双折射和圆双折射时, 单位长度的等效相位延迟量并不等于其固有的线双折射, 等效旋光角也不等于其法拉第旋转角, 它们同时都与光纤的固有线双折射和磁场引起的圆双折射相关联。且在不同级联顺序的两种等效模型中, 等效相位延迟器的快轴方向都不与光纤的双折射主轴重合, 而是分别向两个相反的方向偏移一定的角度, 偏移角为等效旋光角的一半。