A new single-polarization optical fiber

In the single-polarization optical fiber, two isolated stress-applying parts contribute to radiate one of the two orthogonal polarization modes due to the asymmetrical geometric-index effect in addition to a stress-induced birefringence effect without bending the fiber. The loss spectra for x- and y-polarizations and the length dependence of the crosstalk show that the present fiber exhibits single-polarization characteristics     

An asymmetric dual-core single-polarization single-mode photonic crystal fiber coupler

A vectorial finite element method (VFEM) is adopted to investigate the novel single-polarization single-mode (SPSM) photonic crystal fiber (PCF) coupler which has asymmetric dual-core and two lines of enlarged air holes. It is demonstrated that the SPSM region of the designed fiber can be more than 250 nm wide with a set of optimized air-hole parameters and the width of the SPSM region could change slightly by fine adjustment of the inner large air holes. The coupling length between the odd and even x-polarization modes is also investigated through fine-tuning the large and small air-hole diameters.     

Simulation of the properties of a single-polarization microstructured optical fiber

For the first time, the properties of a single-polarization microstructured fiber exhibited over a broad spectral range have been numerically simulated. The simulation was performed via the multipole method adapted to asymmetric structures. A structure with the highest values of birefringence and dichroism known to date has been proposed and investigated.     

Rapid continuous tuning of a single-polarization fiber ring laser

We have developed and studied what we believe is the first fiber laser operating in a single polarization at 1550 nm with PM fiber output and capable of wavelength tuning over a 20-nm bandwidth in less than 50 μs. The fast wavelength tuning speed in a fiber laser is achieved by incorporating an acousto-optic tunable filter into the laser. The same filter is used in an optoelectronic feedback loop to suppress the relaxation oscillations induced by wavelength transitions     

A novel single-polarization single-mode photonic crystal fiber with circular and elliptical air-holes arrays

A novel single-polarization single-mode photonic crystal fiber (SPSM-PCF) with circular and elliptical air-holes is proposed. The characteristics of the proposed SPSM-PCF are investigated by using a full-vector finite element method (FEM) with perfect matched layer (PML) boundary conditions. The results show that the SPSM operation is achieved with wider band, and the total dispersion profile of the SPSM-PCF is dispersion-flattened from 1.193 μm to 1.384 μm. This dispersion property makes the proposed SPSM-PCF useful for various applications, such as optical transmission and dispersion compensation for conventional fiber at long wavelength band with 500 nm negative dispersion region. It indicates that this is a good solution to realize broadband SPSM operation.     

椭圆孔正方形点阵单偏振单模光子晶体光纤的设计

设计了一种椭圆空气孔正方形点阵单偏振单模光子晶体光纤,并以聚甲基丙烯酸甲酯为基材,利用基于棱边/节点混合元的全矢量有限元法对该光纤进行了数值模拟。结果发现,其偏振模场、快轴模和慢轴模截止波长完全依赖于光纤的结构参数;通过优化光纤的结构参数,发现该光纤传输基模的一个偏振态（慢轴模）在0.62μm至0.70μm可见光波长范围内;若调整该光纤结构具有9圈椭圆空气孔时,其偏振模约束损耗在波长0.65μm处可以降至0.13dB/m。该聚合物基低损耗单偏振单模光子晶体光纤可以有效消除传统保偏光纤固有的偏振串扰和偏振模色散。     

Propagation characteristics of a single-polarization optical fiber with an elliptic core and triple-clad

This paper gives the propagation characteristics of a single-polarization optical fiber with an elliptic core and triple-clad. This fiber is designed so as to satisfy the zero total dispersion at the operating wavelength of 1.55 /spl mu/m in the single-polarization region. Thus far, we had studied the n propagation characteristics of single-polarization optical fibers with pits between an elliptic core and the outer cladding (Type-1) and with pits alongside the major axis of an elliptic core (Type-2). In this paper, it is found that a single-polarization optical fiber with an elliptic core and triple-clad has better propagation characteristics compared with Type-1 and Type-2. When the relative index difference between the core and the outer cladding is 0.5%, the main comparison results are as follows: 1) The minimum wavelength sensitivity of the total dispersion can be reduced by approximately 1/3 of those for Type-1 and Type-2, and 2) the single-polarization bandwidth is 2.2 times larger than those of Type-1 and Type-2.     

A single-polarization optical fiber of hollow pit type with zerototal dispersion at wavelength of 1.55 μm

This paper gives a design method for the single-polarization optical fiber which satisfies simultaneously the wide single-polarization bandwidth, the large modal birefringence, and the zero total dispersion at the wavelength of 1.55 μm. As a type of single-polarization fiber, the optical fiber with two hollow circular pits across the core-clad interface is proposed and designed. The normalized power (=Δ the power in the core/the total power) in the core is also evaluated for the designed fibers. It was found from the numerical analysis that when the zero total dispersion is satisfied at the wavelength of 1.55 μm, the maximum modal birefringence of 1.133×10^-3 and the maximum single-polarization bandwidth of 100.6 nm are attained for the relative index difference of 1.6%. Then the normalized power in the core is 0.859     

Design of single-polarization single-mode photonic crystal fiber at 1.30 and 1.55 /spl mu/m

Single-polarization single-mode (SPSM) operation of a highly birefringent (HB) photonic crystal fiber (PCF) is investigated in detail by using a full-vector finite-element method (FEM) with anisotropic perfectly matched layers (PMLs). The cutoff wavelengths of the two linearly polarized principal states can be designed by varying the structure parameters of the PCF. The confinement loss and splice loss to standard single-mode fiber for particular SPSM PCFs are calculated and optimized at both 1.30 and 1.55 /spl mu/m.     

Butterfly model of single-polarization fibers

An exact analysis of propagation along practical single-mode single-polarization fibers is difficult and involves extensive numerical analysis. The authors present a simple refractive-index profile-the butterfly profile-which exhibits the key features of single-polarization operation, but possesses exact analytical solutions of the scalar wave equation for its modes, enabling such quantities as fundamental-mode cutoff and birefringence to be readily evaluated. The accuracy of perturbation solutions based on axisymmetric profiles can also be determined. By incorporating stress anisotropy, the relative values of cutoff for the two polarizations of each mode are shown to be in quantitative agreement with measured values for the bow-tie fiber     

Dual-polarization versus single-polarization MIMO channel measurement results and modeling

This paper presents a simple multiple-input-multiple-output (MIMO) channel model that predicts the eigenvalue distribution and hence, the capacity of MIMO systems using vertically polarized and dual-polarized transmit-antenna configurations with dual-polarized receive antennas. The channel model is verified using broadband outdoor channel measurements taken by a 2 x 3 MIMO system in the 2.5 GHz band.     

硅基二氧化硅单模单偏振光波导的设计

在不增加工艺难度的前提下,利用硅基二氧化硅光波导的双折射效应并结合有效折射率方法, 设计了一种新型单模单偏振波导, 使得两个正交偏振模式中的TM 模式被截止, TE 模式可以通过. 利用三维有限差分光束传输法(3D -BPM ) 进行数值模拟,结果显示,对于TM 模式消光比可高达到50dB 以上.此种结构的光波导可以直接制作偏振器, 同时还易与其他波导器件集成.     

Design of three-dimensional silica on a silicon single-mode single-polarization waveguide

We present a design of three-dimensional(3D) silica on a silicon single-mode single-polarization waveguide (SMSPW) by taking into consideration the induced birefringence effect of the silica.This can cut off the TM mode and transmit the TE mode.The characteristics of the light propagating across the polarization maintaining waveguide were simulated by 3D beam propagation methods(3D-BPM).The result showed that the SMSPW has a high extinction ratio over 50 dB for the TM mode.Without increasing the complexi...     

Quantitative comparison of classification capability: fullypolarimetric versus dual and single-polarization SAR

Addresses the land-use classification capabilities of fully polarimetric synthetic aperture radar (SAR) versus dual-polarization and single-polarization SAR for P-, L-, and C-band frequencies. A variety of polarization combinations are investigated for application to crop and tree age classification. Based on the complex Wishart distribution for the covariance matrix, maximum likelihood classifiers for all polarization combinations are used to assess quantitative classification accuracy. Thus, this allows optimally selecting the frequency and the combination of polarizations for various applications     

Theory of resonant absorption effect and its application tosingle-mode single-polarization fibers

A slight deviation from the resonant condition virtually stops the exchange of energy between two parallel fibers. When one fiber is birefringent, and the other isotropic and lossy, the energy of only one polarization mode swaps back and forth between two fibers and is eventually absorbed. The scalar wave equation is used to investigate the resonant effect. It is found that energy conservation is an intrinsic property of the solution of the scalar wave equation for any trial function, and that standard coupled mode equations obtained from Maxwell's equations can be derived from the scalar wave equation in an exact way. The resonant effect discussed can provide very high extinction ratio at extremely low penalty of additional loss. For example, an extinction ratio of 1.2×10⁴ dB with a penalty of 0.2 dB can be expected after 1-km transmission for waveguide parameters common in fiber optics     

基于光纤锥和多模渐变光纤的马赫-曾德尔干涉仪的传感特性研究

提出了一种基于光纤锥和纤芯失配光纤结构的马赫-曾德尔干涉(MZI)传感器。在距离单模光纤(SMF)锥25mm处熔接一段长30mm的多模渐变光纤(GI MMF),形成SMF-光纤锥-SMFGI MMF-SMF结构。其中,光纤锥起到增加包层模能量的作用,GI MMF为传感臂。传感器外界环境温度、折射率及应力的改变都会使传感器的纤芯基模和包层模的光程差发生改变,从而引起传感器干涉谱发生变化,通过监测干涉谱的变化可以实现对外界物理量的测量。实验研究结果表明,当环境溶液温度在30~89℃范围内变化时,传感器的温度灵敏度为78.6pm/℃,线性度为0.997;环境溶液折射率在1.333~1.394变化范围内,传感器的折射率灵敏度为81.48dB/RIU,线性度为0.989;轴向应变在0~933.3με变化范围内,传感器的应变灵敏度为0.33×10-2 dB/με,线性度为0.998。本文传感器可以实现多个物理量的同时区分测量。     

A high-stability fiber amplifier source for the fiber opticgyroscope

We demonstrate an erbium-doped fiber amplifier (EDFA) source for the fiber gyroscope with an overall mean wavelength stability of four parts per million. This source, which amplifies the gyroscope signal before detection, is shown to be more stable than a similar single-pass source in a standard configuration. The effects of varying the fiber temperature, pump power, pump wavelength, gyroscope feedback power and signal polarization state on the output mean wavelength are individually explored. Experimental results are in excellent agreement with simulations     

A poled electrooptic fiber

A simple fabrication technique, readily extensible to volume manufacturing, is presented to produce an electrooptically active fiber segment that can be simply integrated into optoelectronic devices. The fabrication technique offers a dielectric isolation structure surrounding the fiber to allow high field poling, a pair of electrodes used both for poling and for inducing an electrooptic effect that can be lithographically defined for either velocity-matched, high speed RF modulation or quasiphasematched three-wave mixing interactions, and ends of the fiber unaffected by the fabrication and available for splicing with additional fiber sections. An electrooptic coefficient, including overlap between the nonlinearity and the fiber mode, as high as 0.3 pm/V was obtained by combined temperature/electric field poling.     

保偏光纤饱和吸收体单频窄线宽光纤激光器

研制了一种基于保偏(PM)光纤可饱和吸收体结合光纤光栅Fabry-Perot(FBG F-P)标准具的单频窄线宽光纤激光器.该激光器以高增益掺Er3+光纤(EDF)作为增益介质,采用行波环形腔消除空间烧空效应,并结合FBG F-P标准具选模,实现激光器单频运转.用一段PM EDF作为可饱和吸收体抑制跳模,以获得高效、稳...     

适于光纤到家庭的新型光纤：多芯单模光纤

本文介绍法国电信公司和阿尔卡特公司开发的多芯单模光纤,重点介绍了４芯单模光纤的结构设计、预制棒制造工艺、拉丝技术和光纤特性,也介绍了该新型光纤在ＦＴＴＨ用途中的技术经济优越性。