Quantum Statistical Theory of Polarization Mode Dispersion

Polarization mode dispersion is modelled as decoherence of polarization under the disturbance of environment and the coupling with frequency. This model is described by the quantum master equation and the Langevin equation. It can be predicted that the optical beam is depolarized exponentially in a fibre and the differential group delay （DGD） is proportional to the square root of the propagation distance. The distribution of the DGD can also be calculated.     

Distributed Measurement of Birefringence by P-OTDR Assisted with Piezoelectric Polarization Controller

We propose a new polarization sensitive optical time domain reflectometry （P-OTDR） setup assisted with a piezoelectric polarization controller （PPC）. The input state of polarization can be changed by varying the voltage of PPC without any rotatable instrument, and only one optical receiver is used to detect the backward beam. We measure a single mode fibre and get the distribution of birefringence along the SMF.     

Passive polarization-controlled all-fiber gyroscope and other interferometric architectures

A novel all-fiber gyroscope architecture is disclosed making use of the author's U.S.-patented Passive Polarization Control (PPC) invention to stabilize the polarization state of the counter-propagating beams in the rotating Sagnac fiber loop. The PPC is simply a piece of variably spun birefringent optical fiber capable of transforming a circularly polarized light into a linearly polarized light that automatically aligns itself along a principal axis of the fiber. The all-fiber gyroscope architecture uses two cascaded directional couplers operating on circular SOP, thus providing an “SOP matching” with the PPC-terminated fiber loop. Re predicted PPC performance has been confirmed experimentally in a laboratory.     

Cascaded Optical Buffer Based on Nonlinear Polarization Rotation in Semiconductor Optical Amplifiers

A cascaded buffer based on nonlinear polarization rotation in semiconductor optical amplifiers is proposed, which is suitable for fast reconfiguration of buffering time at picoseconds. With the proposed buffer, sixty different buffer times are demonstrated at 2.5Gb/s.     

利用旋转波片组实现偏振变换器的两种新方法

偏振变换器作为一种重要的光学器件．以其高偏振变换精度、低成本、低插入损耗以及控制算法简单的特性在相干光纤通信和高速光纤通信领域具有十分重要的地位。提出了利用两个λ／4波片和一个λ／2波片的三波片组合实现任意偏振态变换的新方法。用改进的三维庞加莱球方法—偏振态投射平面的二维几何方法分别推导出了λ／4 λ／4 λ／2组合以及λ／2 λ／4 λ／4组合实现任意偏振态变换时每个波片的位置参量计算公式。研究结果表明：两个λ／4波片和一个λ／2波片的任意组合都可以实现任意偏振态的变换;用偏振态投射平面的几何方法处理偏振变换的相关问题比庞加莱球方法和矩阵处理方法简洁明了。研究结果为偏振变换器的设计提供了理论依据。     

Theoretical Design of Single-Polarization Single-Mode Microstructured Polymer Optical Fibres

Using the full-vector plane-wave expansion method, a kind of PMMA-based polarization-maintaining microstructured optical fibre （PM-mPOF） is theoretically studied. Dependence of the cutoff wavelengths of the two orthogonal polarization states （polarized along the two principal axes of PM-mPOF） on the structure parameters of the fibre is investigated in detail A single-polarization single-mode （SPSM） PM-mPOF working in the visible region is designed and optimized with the result of the maximum SPSM bandwidth of 140nm.     

Polarization properties of Rayleigh backscattering with a high degree of coherence in single-mode fibers

The state and degree of polarization (SOP, DOP) of Rayleigh backscattering (RB) are analyzed by using Jones calculus for the case the source coherent length is larger than the fiber length. It shows that the SOP of RB is the same as the SOP of input light, and the fiber disturbance does not influence the SOP of RB. The DOP of RB is also the same as that of input light. The corresponding experiments have been carried out, and the results agree well with all the predictions.     

Coherent, polarization and temporal properties of self-frequency shifted solitons generated in polarization-maintaining microstructured fibre

Coherence of both self-frequency shifted solitons and short-wavelength non-soliton radiation generated in a micro-structure fibre was investigated experimentally for the first time. Their spectral, temporal and polarization characteristics were studied as well. We found the solitons generated in 30-cm-long fibre pumped with 50-fs pulses at 795 nm and 835 nm from Ti:Sapphire oscillator to be coherent, whereas degree of coherence of blue-shifted radiation was amounted to 0.25–0.57 depending on wavelength.     

投影光学系统中的偏振像差分析

当光束斜入射时,光学薄膜存在一定的偏振效应。在飞利浦棱镜系统中,当一定大小孔径角的照明光束斜入射到分色合色薄膜后,S偏振分量和P偏振分量存在一定的相位差,使得线偏振光变成椭圆偏振光。利用琼斯矩阵偏振光线追迹的方法,分析了投影光学系统中由于两偏振分量相位差引起的偏振像差,以及它与暗态泄漏光强和系统衬比度的关系。得出了系统出瞳面上的光波偏振特性,以及在不同大小孔径角的照明光束入射下偏振像差的变化。分析了膜厚监控误差对光学系统偏振像差的影响,发现膜厚监控误差对偏振像差和系统衬比度有很大的影响。所使用的分析方法可以应用于其他大口径光学系统。     

基于半导体光放大器偏振旋转的全光缓存器

全光缓存器可实现数据包在光域内的缓存,是全光路由、伞光计算以及全光交换的关键部件之一.提出了一种基于半导体光放大器(SOA)中非线性偏振旋转(PR)的光纤环型全光缓仃器结构;提出了一种利用偏振主态(PSP)寻找两个正交线偏振态以及在线实时测量光纤中偏振态的方法.通过改变SOA的注入电流,实现了对两个正交偏振态转化的控制,利用这两个正交的线偏振态,实现了信号的"写"人和"读"出.利用该结构的缓存器,实现了2.5 Gb/s的1024 bits数据包6圈的缓存.缓存后的信号波形良好.     

Study of the stability of polarization mode dispersion in fibre

Polarization mode dispersion (PMD) is the ultimate limitation to high bit-rate fibre communication system. The stability of PMD is very important to its measurement and compensation. This paper puts forward a method to measure the stability of PMD by measuring the stability of the state of polarization (SOP) and introduces the conception of time evolution vector (TEV) of SOP. We observe the fact that the regularity of the principal state of polarization changing with time is the same as other SOPs‘‘, if we neglect the dependence of TEV on wavelength. We also measure the SOP‘‘s stability of some fibres with different lengths, and obtain results of PMD changing with time.     

基于激光偏振特性的水下声信号探测方法研究

水下航行体辐射的声波传播到水-空气分界面上时,会在水表面形成微扰,使水表面元产生微倾角.提出一种利用激光偏振特性对水下声信号进行探测的方法,不直接利用散射光强信息,而是利用激光在布儒斯特角附近入射水表面时,反射光偏振特性随入射角剧烈变化的特点对水表面微扰进行高精度探测.建立了该方法的理论模型,得到了入射波、出射波垂直分...     

Polarization of light and topological phases

The phase shifts experienced by a polarized light wave when it propagates through media with arbitrary birefringence, dichroism and depolarizing properties, while on the one hand provide the basis for a variety of optical devices and experiments, on the other provide a powerful means of understanding unitary evolution, nonunitary evolution and decoherence of two-state quantum systems by virtue of a mathematical isomorphism of the two systems. These also help understand aspects of evolution of classical systems under the group of rotations in three-dimensional space, namely the SO(3) group, by virtue of its homomorphism with the group SU(2) governing unitary evolution of polarized light waves. In this review we present a survey and analysis of recent work on topological phases with polarization of light which has revealed several counterintuitive features of such phase shifts such as 2nπ anholonomies, nonlinear and discontinuous behaviour originating hi singularities, peculiar spectral dependence, etc. We point out several areas where these results may find practical application, for example endless phase correction in interferometric sensors, fast switching spatial light modulators, phase shifters with unusual chromatic properties, phasing of antenna arrays, etc. Several useful theoretical insights relevant to polarization optics, quantum mechanics, classical mechanics and other areas of physics, obtained from the work on polarization states are described and some directions for future work are indicated.     

全光学偏振自动控制器

本文报道新近研制的一种单模光纤偏振控制顺，该器件采用全光学的方法对光纤输出光信号的任意偏振态进行自动调整，使其成为一沿给定方向偏振的线偏振态，器件插入损耗小于１ｄＢ，与半导体激光放大器耦合损耗可小于５．５ｄＢ，其偏振灵敏度不大于０．５ｄＢ．     

Coherent recombination of laser beams with interferometrical phase control

A HeNe laser beam is split into four component beams which are subsequently transmitted through four polarization-preserving monomode fibres. At the end of the fibres the emerging beams are coherently recombined in pairs in two steps using inverse beamsplitter cubes. The unavoidable phase differences within each pair of beams, which are caused by temperature and pressure fluctuations in the fibre environment, are detected interferometrically at the fibre ends. Using homodyne techniques, these differences are measured and compensated for by lengthening the optical path in the individual fibres with piezo-electric stretching. With appropriate adjustment of the relative phases the emerging beams can be superimposed onto each other so as to re-form one single coherent beam.     

Pulse Evolution Characteristics in Self-Similar Mode-locked Fibre Laser

A self-similar mode locked fibre laser is studied based on a numerical model. By introducing a dimensionless factor k to characterize the pulse shape, the self-similar pulse evolution, formation and the temporal and spectral shape changes due to the elements in the cavity are investigated throughout the laser cavity. The results show that in the self-similar mode locked fibre laser, self-similar pulse is first formed in the single-mode fibre, which is then amplified in the gain fibre. Gain bandwidth has a small influence on pulse shape, so high energy self-similar pulse can be obtained after amplification. Because net cavity dispersion directly influences the pulse width as well as peak power after compression by a pair of gratings, which can determine the pulse self-similar evolution, it is very important to control the net cavity dispersion to a certain range to obtain self-similar pulses.     

Impact of spin-zero particle-photon interactions on light polarization in external magnetic fields

If the recent PVLAS results on polarization changes of a linearly polarized laser beam passing through a magnetic field are interpreted by an axion-like particle, it is almost certain that it is not a standard QCD axion. Considering this, we study the general effective interactions of photons with spin-zero particles without restricting the latter to be a pseudo-scalar or a scalar, i.e., a parity eigenstate. At the lowest order in effective field theory, there are two dimension-5 interactions, each of which has previously been treated separately for a pseudo-scalar or a scalar particle. By following the evolution in an external magnetic field of the system of spin-zero particles and photons, we compute the changes in light polarization and the transition probability for two experimental set-ups: one-way propagation and round-trip propagation. While the first may be relevant for astrophysical sources of spin-zero particles, the second applies to laboratory optical experiments like PVLAS. In the one-way propagation, interesting phenomena can occur for special configurations of polarization where, for instance, transition occurs but light polarization does not change. For the round-trip propagation, however, the standard results of polarization changes for a pseudoscalar or a scalar are only modified by a factor that depends on the relative strength of the two interactions.     

Spectroscopic polarimetry with a channeled spectrum

We describe a novel method for the spectroscopic measurement of the state of polarization (SOP) of light. A pair of thick birefringent retarders is incorporated into the spectroscopic polarimeter, so the generated channeled spectrum is composed of three quasi-cosinusoidal components carrying the information about the SOP of the light that is being measured. Fourier inversion of the channeled spectrum provides significant parameters for determination of the spectrally resolved Stokes parameters of light. No mechanically movable components for polarization control or active devices for polarization modulation are used, and all the Stokes parameters can be determined at once from only the single spectrum. The effectiveness of this method is demonstrated by the generation of elliptically polarized light whose SOP varies with wave number.     

Propagation of Single-Mode Fibre Laser Beams through an Optical ABCD System with Circular Aperture at the Fibre Output End

Based on the expansion expression of the fundamental mode of a single-mode fibre in terms of Laguerr-Gauss modes, the propagation of a beam of a weakly guiding fibre laser through an opticM ABCD system with a circular aperture at the fibre end is studied. The results show that there is much difference between the propagation of the laser beam described by the expansion expression and by the Gaussian mode approximation. The depth of focus of the laser beam is longer than that of the Gaussian modes.     

Polarization mode dispersion in single mode optical fibers due to core-ellipticity

The variation of polarization mode dispersion (PMD) with V-parameter in single mode optical fibers due to core-ellipticity is studied by performing numerical simulations taking into account both geometrical and thermal-stress-induced birefringences as well as the variation of fiber refractive indices with wavelength. Simple empirical relations are given for calculating the mean PMD for any value of core-ellipticity and V-parameter of a standard single mode fiber. It is observed that the mean PMD saturates for V ? 1.8 leading to very small second order PMD.