高双折射光纤双折射温度特性新型测量方法研究

根据高双折射光纤Sagnac环镜的透射谱函数推导出其峰值波长与双折射的关系,通过测量峰值波长随温度的漂移量推算出高双折射光纤双折射的温度系数,从而提出了一种测量高双折射光纤双折射随温度系数的新方法.本文设计的方法结构简单,易于操作,只需要搭建一个简单的Sagnac环镜而无需其它特殊的装置,与写制光栅的方法相比简化了测量的复杂度和降低了设计成本,具有设计灵活和应用广泛的优点.     

Dependence of birefringence on elliptical-hole orientation in photonic crystal fibers

In this paper, the dependence of birefringence on the orientation of elliptical holes in triangular-lattice elliptical-hole photonic crystal fibers (PCFs) is investigated numerically. A resonant enhancement of birefringence between the anisotropic lattice arrangement and oriented elliptical holes is observed, and the birefringence varies periodically with the elliptical-hole orientation. When the major axes of adjacent elliptical holes are parallel, the birefringence approaches the maximum. Based on the numeric analysis, a novel highly birefringent PCF is proposed, and the maximum modal birefringence of 0.086 is achieved.     

Stress-optic effects, birefringence, and reduction of birefringenceby annealing in fiber Fabry-Perot interferometers

The effects of inherent fiber birefringence, packaging stresses, and stress tuning on the behavior of a fiber Fabry-Perot interferometer are examined. A polarization doublet due to birefringence is observed. For birefringence of 1 ps/km, the doublet spacing is 40 MHz, at 1.5-μm wavelength, independent of the FFP finesse or free spectral range, and is due mainly to the inherent fiber birefringence. It was found that annealing depressed-cladding single-mode fiber reduced the fiber birefringence, for example, from 40-80 MHz to 15-25 MHz. Where the bandpass of the FFP is greater than the birefringence doublet, this device should be polarization insensitive for most applications     

一种Sagnac干涉仪结构的光子晶体光纤温度传感器

采用Sagnac干涉仪结构,设计了一种高双折射光子晶体光纤环镜温度传感器。光子晶体光纤温度稳定性好,通过向高双折射光子晶体光纤空气孔填充热光系数高的液体材料乙醇,从而实现温度传感的目的。采用平面波展开法,分析了高双折射光子晶体光纤的双折射与传输波长和温度的关系。理论分析表明,填充乙醇后,高双折射光子晶体光纤的双折射随着传输波长和温度的增加而增加,且双折射与温度成线性关系。实验中将一段填充乙醇的高双折射光子晶体光纤与3 dB耦合器熔接制作成Sagnac干涉仪结构的光纤环镜,当温度从 45 ℃升至80 ℃时,光谱仪上观察到凹点λi向短波方向漂移了309.280 nm,温度灵敏度高达8.837 nm/℃。     

领结型和椭圆型保偏光纤的应力和模式分析

应用有限元方法对领结型和椭圆型保偏光纤的热应力双折射特性和模式双折射进行了分析,给出了这两种保偏光纤的应力和双折射分布规律.对领结型保偏光纤,研究了纤芯的双折射和模式双折射随着应力区离纤芯距离的变化规律;对椭圆型保偏光纤,研究了纤芯的应力双折射和模式双折射随包层椭圆度的变化规律;分析了光纤应力区结构对纤芯双折射大小和均匀性的影响,并将应力诱导双折射与模式理论计算结果进行了比较.     

椭圆芯扁六角聚合物光子晶体光纤的偏振特性

采用全矢量定域基函数模型,以聚合物PMMA为基材,研究了椭圆芯三角点阵扁六角结构光子晶体光纤(Photonic crystal fibers,PCFs)的偏振特性,分析了其相位模双折射和群模双折射与相对孔间隔比的依赖关系,并与椭圆芯三角点阵正六角结构PCFs的研究结论进行比较;研究发现,椭圆芯扁六角结构PCF的偏振特性强烈的依赖于光纤的结构参数,由于色度色散的存在,在短波长段,群双折射远远高于相位模双折射,通过适当调节光纤的相对孔径和相对孔间隔比,有望在给定波长实现高双折射和零偏振模色散单模运行.该研究为高双折射聚合物光子晶体保偏光纤的制备提供了理论依据.     

A novel high birefringence equal diameter circular-hole photonic crystal fiber

A novel equal diameter circular-hole photonic crystal fiber (PCF) with high birefringence is proposed and numerically analyzed by employing the finite-element method. The proposed PCF’s birefringence is 10-3, which can reach 2 orders higher than that of traditional high birefringence fiber, and this equal diameter circular-hole structure reduces the difficulty of the actual drawing process. The effect of different parameters on the birefringence of this PCF is investigated, and the application of the Sagnac interferometer based on fiber filling technology in temperature sensing is studied. The result shows that the high birefringence PCF can be used in both optical communication and optical sensing fields.     

单模光纤拉伸器分布式双折射特性实验研究

在偏振敏感光纤系统中,光纤双折射是重要的参 量。基于压电陶瓷的单模光纤(single-mode fiber,SMF)拉伸器是光纤系统中引入应变、光程或 相位变化等常用的器件,而少有人关注过光纤拉伸器引入的双折射特性。本文提出基于分布 式偏振分析的SMF拉伸器双 折射特性表征方法,结合全穆勒矩阵分析和光频域反射仪技术,可以得到SMF拉伸器缠 绕光纤的分布式双折射特性。实 验得到:在光纤拉伸器使用过程中,光纤双折射随驱动电压增大而增加;当光纤拉伸器缠绕 光纤表面不平整时,可引入更高 的基底双折射,且在施加驱动电压时,基底双折射增加更加明显;设计合适的拉伸机构和光 纤缠绕方法,能有效地避免光纤拉 伸器使用过程中双折射的改变,但可能会引入较强的基底双折射。本文研究结果对于在偏振 敏感光纤系统中使用光纤拉伸器时系统性能的评估及优化具有指导意义。     

Birefringence in bent single-mode fibers

Changes to field properties when an optical fiber is bent are considered. A formula is obtained for the geometrical birefringence in a single-mode fiber due to bending, and is explicitly evaluated for a Gaussian field approximation, giving a simple analytic expression; it is also evaluated for more exact fields. Scalar theory is not sufficient to describe this birefringence, as reported previously, and vector or polarization corrections must be included in the theory. This birefringence is several orders of magnitude less than stress-induced bending birefringence     

圆芯边孔光纤模式场分布和双折射的研究

对圆芯边孔光纤双折射的研究结果进行报道.使用有限元方法建立了包括计算圆芯边孔光纤横截面应力分布、折射率分布和双折射的模型,计算了圆芯边孔光纤的模式场分布、几何双折射和应力致双折射.研究表明,圆芯边孔光纤的应力致双折射很小,这是圆芯边孔光纤自身的特殊结构造成的.比较了几种不同边孔形状的光纤的双折射,提出了圆芯边孔光纤的优化结构.     

Finite-element analysis of birefringence in azymuthally inhomogeneous optical fibre

This communication reports the existence of a general purpose finite-element analysis program which can be used for the analysis of stress-induced birefringence in a single-mode optical fibre. This is applied to the azimuthally inhomogeneous fibre and it is found that the stress-induced birefringence is an order of magnitude larger than the geometric birefringence in the vicinity of V = 2. Maximum birefringence occurs when equal segments of different indices are used in the core.     

单轴晶体双折射率随温度变化的双光路测量

为了研究单轴晶体最大双折射率在某一波长下随温度的变化情况,根据偏振光干涉的理论分析,推导出了单轴晶体最大双折射率随温度变化的解析式.在此基础上,设计、建立了一套双光路对比测试实验系统.利用该实验系统对石英晶体样品进行测试,获得了其实验数据变化曲线,并总结出了在测试波长下,石英晶体最大双折射率随温度变化的数学式.结果表明,单轴晶体在某一波长下的最大双折射率基本上与温度成线性关系;实验过程中,只要精确调整仪器,并注意控制好实验所需温度,其测量结果是可靠的.     

用于DWDM系统的双折射型Interleaver原理分析

介绍了交叉复用器 (Interleaver)在密集波分复用 (DWDM)光纤通信系统中的作用 ,利用各向异性晶体的双折射和偏振光的干涉分析了双折射型Interleaver器件的原理 ,给出了一种双折射型Interleaver与薄膜滤波器混合结构的DWDM光纤通信系统的概念设计     

向列相液晶双折射特性的研究

考虑包含偶极子相互作用及其关联的分子相互作用势，用统计物理方法讨论了向列相液晶的双折射随波长、温度和偶极关联因子的变化。结果表明，向列相液晶双折射随波长红移和温度升高而减小，而偶极关联因子越大的液晶，双折射越大。     

双折射对孤子传输的影响及其相互作用控制

利用对称分步傅里叶法,数值研究了双折射光纤中孤子的传输特性,分析了孤子脉冲的入射偏振角为30°时两偏振分量群速度失配对孤子传输产生的影响。结果表明,光纤的双折射大小影响着脉冲峰值对时间的漂移程度,双折射越大,峰值漂移越多。如果光纤的双折射具有随机性,峰值漂移被修正,孤子传输的两偏振分量脉冲强度会随着传输距离有强弱不规则的变化,但是两偏振分量的强度变化互相补充,合成强度没有太大的变化,孤子能够稳定的传输。非线性增益可以有效地抑制随机双折射对孤子传输相互作用的影响,使得原本会产生交叠走离的相邻孤子传输不偏离原来的时间槽,实现了对偏振模色散良好的控制作用。     

类矩形保偏光纤应力双折射分析

采用有限元方法对“类矩形”保偏光纤的应力双折射进行了分析,给出了保偏光纤横截面上的应力分布图形及应力双折射分布曲线;应用全矢量电磁场有限元方法,计算了保偏光纤的两个偏振模场的分布、传输常数及模式双折射.在给定模拟条件下,纤芯的应力双折射约为 3. 33×10-4,其模式双折射约为 3. 72×10-4.计算结果表明,这种“类矩形”保偏光纤与其它保偏光纤相比,有几个明显的优点,即有更佳的应力传递效果、均匀的应力场分布、更大的应力双折射.     

Recent Advances in Birefringence Studies at THz Frequencies

In the last few years, various studies on terahertz (THz) birefringence have been presented, based on polarization-sensitive THz time-domain spectroscopy. The field of THz birefringence is a wide one covering several aspects, such as different materials exhibiting THz birefringence, polarization-sensitive THz technology, as well as numerous methods for extracting the birefringence properties of a sample from the THz data. Therefore, this paper aims at reviewing recent results on THz birefringence measurements presented in literature, addressing the above aspects and giving an overview of the topic. Moreover, it will focus on the investigation of birefringent fibrous samples, where specific results will be discussed in detail. Altogether, this paper should give a comprehensive view on the recent achievements in the measurements of THz birefringence.     

Birefringence in benzocyclobutene strip optical waveguides

We report the fabrication of benzocyclobutene strip optical waveguides and the measurement of their birefringence properties. To take into account the stress-induced birefringence in the waveguide, we generalize the formulas reported previously for the analysis of strip waveguides. Our experimental results are shown to agree closely with the theoretical calculation. The condition for achieving zero modal birefringence by control of the aspect ratio of the strip of the waveguide is highlighted. The dependence of the birefringence in the waveguides on the temperature is also measured and discussed.     

Measure of twist-induced circular birefringence in long single-mode fibers: theory and experiments

Production defects and external perturbations cause standard telecommunication fibers to be randomly birefringent. Fiber birefringence is the origin of the well-known polarization mode dispersion (PMD), which degrades system performances. The knowledge of birefringence properties may be crucial, especially when problems like development of low-PMD fibers or PMD interaction with optical nonlinearities in very high-capacity systems are faced. Some techniques are known to measure birefringence, and useful results have been obtained for both installed and wound-on-drum fibers. However, measurement of the circular component of birefringence still presents difficulties. In this paper, a new method for circular birefringence measurement is proposed that applies to long single-mode twisted fibers. The technique is based on polarization-sensitive optical time-domain reflectometry. Experimental results are in good agreement with the theoretical analysis.     

Measurement of the birefringence of UV-written channel silicawaveguides by magnetooptic polarization-mode coupling

We report the measurement of the birefringence in integrated-optical waveguides using magnetooptical coupling between the two principal polarizations of the fundamental mode. We demonstrate this measurement technique for directly ultraviolet (UV)-written channel waveguides in silica on-silicon and silica-on-silica. The dependence of the waveguide birefringence on the UV-writing power and UV polarization is investigated. The results are compared with the birefringence of etched waveguides in comparable material systems. An analytical formula for the form birefringence in buried channel waveguides is developed, and measured data are compared with theoretical results