Automated fusion-splicing of polarization maintaining fibers

An advanced splicing technique for polarization maintaining (PM) fibers has been derived based on the polarization observation by lens-effect-tracing (POL) method. With this technique, azimuthal alignment on common types of PM fibers can be automatically performed in a passive way by an automated fusion splicer. Because the method permits an accurate estimation of the splice's extinction ratio before and after actual splicing, the quality of the splice call be estimated without having to make an active measurement. The experiment results illustrated in the paper show a mean extinction ratio 32.2 with 2.73 dB standard deviation and mean difference between measured and estimated extinction ratio 0.18 dB, respectively, for six different types of PM fibers     

长波长细径保偏光纤的制作

通过介绍长波长熊猫型细径保偏光纤的制作工艺过程.分析细径保偏光纤制作的技术难点,初步解决了细径保偏光纤制作工艺中的问题,制作出了长波长熊猫型细径保偏光纤样品.所制作的保偏光纤在1550nm波长下损耗小于1dB/km,偏振串音达到近-28dB/km.     

Analysis of the polarization behavior of hybrid modes in highlybirefringent fibers

The polarization properties of hybrid waveguide modes in highly birefringent fibers are theoretically and experimentally investigated. The Jones spatial polarization matrix of the fiber for a hybrid mode is derived. Both monochromatic and quasimonochromatic cases are considered. The case of stress nonuniformities and its consequences to polarization preservation is addressed. The problems related to the polarization preservation along single- and two-mode fibers are discussed     

Numerical analysis of residual stresses in preform of stress applying part for PANDA-type polarization maintaining optical fibers

This study is concerned with numerical simulation of the mechanisms responsible for formation of technological and residual stresses in preforms of non-uniformly doped silica stress applying rods for optical fibers of PANDA-type caused by cooling and etching of the upper layers. The relationships between the doping degree and the rod radius meeting the strength criterion have been established. It has been found that doping of the stress applying rod with doping additives compensating the refractive index increases the level of the stress state. To take account of this effect a set of doping relationships acceptable for compensated rods has been proposed.     

保偏光纤拍长的测量方法

介绍了保偏光纤拍长测量的几种常用方法,就其测量原理,试验装置及优缺点分别进行了较为详细的分析和说明.并就目前多数测量方法适用于高双折射光纤的不足,介绍了一种较好的测量低双折射光纤拍长的方法.     

Anisotropic polarization maintaining optical fiber ring resonators

Suppression of the polarization drift of optical fiber ring resonators is investigated both theoretically and experimentally by employing anisotropy in a polarization maintaining fiber ring. A general analytic expression for the transmission of the device is derived allowing the fiber modes to exhibit any combination of polarization crosstalk, differential loss or differential coupling. The analysis shows that a moderate level of ring anisotropy, such as that of 10 dB in line polarizer or polarization selective coupler, is sufficient to greatly suppress the drift of the eigenstates of polarization (ESOPs), finesse and resonant point, restoring the device's suitability for most practical applications. An inevitable consequence of introducing ring anisotropy is the loss of orthogonality of the ESOPs. This effect limits the anticipated benefit in high sensitivity applications. A practical anisotropic PMRR is demonstrated by inserting a thin film of nematic liquid crystal between the two halves of the polished coupler of the ring. This resonator demonstrates a polarization response immune to environmental perturbations     

Coupled coplanar waveguide with anisotropic substrate

Frequency-dependent hybrid-mode values of the characteristic impedances as well as the effective dielectric constants are presented for the coupled coplanar waveguide with uniaxially anisotropic substrate for the first time. The characteristic impedances are calculated by using two different definitions, that is, the voltage/current and power/voltage criteria, and both of them converge to the quasistatic values in lower-frequency ranges.     

LP modes and ideal modes on optical fibers

The transformation from coupled-mode equations for LP modes to those for ideal modes and the expressions of one set of modes in terms of linear combinations of the other set of modes are studied, using the coupled-mode theory. The expressions (including higher-order corrections) of modal fields and propagation constants for ideal modes are given in terms of those for LP modes in three different cases. Thus, cases where a LP mode can or cannot directly replace a corresponding ideal mode are made clear.     

Coupled mode analysis of polarization volume hologram

We theoretically analyze polarization holographic recording based on photoinduced dichroism and birefringence. Such vectorial recording is achieved by preferentially transforming dye molecules aligned with the incident polarization in dynamic photoanisotropic organic materials. Orthogonal linear and orthogonal circular recording geometries, which produce only pure polarization modulations, are considered. The analytic solutions of the intensity and phase of the recording beams at steady state are derived. The theoretical results indicate the dependence of diffraction efficiency on the photoinduced dichroism and birefringence and on the polarization state of the probe beam. Results of numerical simulation are provided and compared with the analytic solutions     

Explicit birefringence analysis for anisotropic fibers

A hyper-perturbation approach is used to find the Taylor expansion formulas for the dispersion curves of arbitrarily indexed optical fibers. These formulas are then used to give analytically the birefringence characteristics of optical fibers with biaxially anisotropic core and cladding. The dependence of the fiber birefringence on the index difference, index anisotropy, and the normalized frequency is explicitly determined. Simple, accurate analytic formulas have been presented for anisotropic fibers with step- and parabolic-index profiles. Numerical results are in good agreement with the literature results     

Variational analysis of anisotropic graded-index optical fibers

The variational principle for nonstandard eigenvalue problems recently introduced and used for step-index optical fiber analysis by the present authors is extended to anisotropic graded-index optical fibers. It is seen through an example of a round parabolic-index fiber that the choice of trial functions is more delicate than for the step-index fiber because of the more complicated field function. Certain two-parameter approximants, however, appear accurate enough and can be optimized with a simple calculator or desk computer analysis     

Eigenstates of polarization of elliptical single-mode fibers

The degree of polarization of radiation in an elliptical polarization-maintaining fiber and the polarization states of eigenpolarization modes of such fibers have been experimentally investigated in a wide spectral range. It has been shown that the elliptical fibers are uniform, homogeneously twisted fibers with elliptically polarized eigenpolarization modes. The ellipticity of the eigenpolarization mode is independent of fiber length and increases with wavelength, while the azimuth of the eigenpolarization mode is spectrally independent     

基于部分保偏器件的干涉型光纤传感器

在单模光纤构成的干涉型光纤传感器中,存在偏振衰落问题,将导致干涉效率降低.而为了消偏振衰落采用全保偏器件的光纤传感器成本过于高昂,影响其实用性.以马赫.泽德干涉仪为基础,用反馈信号控制偏振控制器加起偏器的结构消除了偏振衰落,构造了基于部分保偏器件的干涉型光纤传感器.实验得到系统输出信噪比稳定在60 dB左右.     

Tunable polarization maintaining fiber Bragg grating based OSNR monitor

A simple optical performance monitoring scheme based on a tunable polarization maintaining fiber Bragg grating is proposed. The proposed technique measures the in-band optical signal-to-noise-ratio through orthogonal polarization detection. The scheme is successfully demonstrated for NRZ-OOK signals at 10 Gb/s with an input dynamic range of around 20 dB. The results show that the performance of the scheme is not sensitive to the effects of chromatic dispersion.     

保偏光纤保密通信研究

利用保偏光纤受到外界干扰时主轴发生变化,从而使其中传输的偏振光的偏振度发生变化的原理,实时检测介入窃听,给编码保密通信增加了一个保密度。由于是比例检出,信噪比高,抗干扰能力强。记录了无究听时系统在-3℃～60℃的背景噪声作为对比检出依据。检出窃听的阈值是裸光纤弯曲半径为8.5mm。     

Coupled modes of multiwaveguide systems and phased arrays

A new theory describing coupled mode propagation in an array of arbitrary optical waveguides is developed. The formulation unambiguously accounts for real and/or imaginary index perturbations and its solutions yield supermode patterns and propagation constants. Several examples of coupled TE slab waveguides are evaluated and the results are shown to compare very favorably with exact solutions. The calculated propagation constants and mode patterns differ quantitatively and qualitatively from those derived from the prior theory. In particular, the supermode gains derived according to the new theory agree very well with exact solutions and predict different supermode ordering and splitting than those derived by the prior theory.     

保偏光纤模式耦合分析及其相干检测

当保偏光纤存在结构不均匀或者受到外部扰动时,将使其内部传输的一部分偏振光耦合到与其正交的偏振态上去。分析了保偏光纤内偏振光模式耦合的原理,给出了基于白光干涉法的偏振模式耦合检测方法,并用迈克尔逊干涉仪对保偏光纤的偏振模式耦合的耦合强度和耦合点发生的空间位置进行了测试。通过步进电机控制迈克尔逊干涉仪扫描臂的反射镜移动,改变干涉仪两臂之间的光程差,来补偿由于偏振耦合而形成的两偏振光从保偏光纤出射时的光程差,实现了对偏振耦合的测量。为提高检测系统的灵敏度,需提高输出信号的信噪比,对光源发出的光进行高频调制,通过频谱搬移和相干解调,有效地抑制了各种干扰和噪声,使输出信号的峰值信噪比提高了5.1 dB,耦合强度测试最小值也由-57.6 dB提高到-62.7 dB,增强了测试系统检测微弱偏振耦合的能力。     

Study of whispering gallery modes in anisotropic single-crystaldielectric resonators

The Rayleigh-Ritz method and the finite element method nongenerating spurious solutions are employed for analysis of whispering gallery modes (WGMs) in cylindrical single-crystal anisotropic dielectric resonators. These methods allow accurate computation of the resonant frequencies, the Q-factors (depending on the dielectric and on the conductor losses), and the electromagnetic field distributions for all WGMs in the presence of additional elements like metal shields, MIC substrate, or supports. Different families of modes are studied both theoretically and experimentally. The mode coupling phenomenon is investigated. A WGM single-crystal quartz resonator is presented having an unloaded Q-factor greater than 30000 at about 100 GHz, including radiation and dielectric losses     

旋转光纤中的拍长与偏振态保持能力

理论分析了旋转光纤在不同参考坐标系中的拍长及其与旋转光纤偏振态保持能力之间的关系——结果表明,旋转光纤没有确切的拍长定义,只有近似的用于描述旋转光纤偏振态保持能力的拍长计算公式。     

熔锥型宽带保偏光纤耦合器的研究

熔融拉锥型宽带保偏光纤耦合器的制造工艺及其工艺参数的设置,对器件的性能有直接的影响.根据熔融拉锥型宽带保偏光纤耦合器的原理和光纤电磁理论,结合试验事实,对熔融拉锥的工艺进行了总结:实现了常规熔融拉锥型宽带保偏光纤耦合器的制作,并对产品进行了测试,完成了预期研究目标.