高准确度熊猫保偏光纤自动定轴技术

保偏光纤偏振轴的检测和对准是保偏光纤应用中的关键技术.为提高基于端面成像的偏振轴检测方法的检测精度,以熊猫型保偏光纤为研究对象,采用基于曲面拟合的亚像素边缘检测算法和椭圆拟合算法提高检测的准确度,采用多次测量取平均法提高检测的精确度;利用检测结果的正态分布特性,提出一种基于概率的偏振轴定轴方法.搭建了保偏光纤自动定轴系统并进行实验,准确性验证实验结果表明:亚像素边缘检测方法平均可以减小45%的偏差,而拟合椭圆相较拟合圆平均可以减小15%的偏差;精确性验证实验表明采用多次测量取平均的方法可以有效减少检测结果的离散程度;定轴实验的结果表明,基于概率的偏振轴定轴方法可以达到优于0.1°的定轴准确度.     

船舶内燃机制造与维修专业教学改革实践

该文介绍了船舶内燃机制造与维修专业教学改革的指导思想和目标；专业教学改革的基本思路与做法；专业教学改革取得的主要成果。     

面子维护的语用策略——汉语中不同意的间接表达

中国人经常用以维护他人面子的策略之一是尽量使用间接、委婉和模棱两可的言词。在汉语中间接表达不同意的类型有模糊含蓄法、移情表达法、假托直言法和转移话题法(移花接木法)。本文就是从维护面子的角度,探讨汉语中间接地表达不同意的这几种类型的语用策略。     

黄金分割律与人的形体美

本文论述了黄金分割律与人的形体美和养生之道之间的关系。     

Characteristics of Guided Acoustic Wave Brillouin Scattering in Polarization Maintaining Fibers

Characteristics of guided acoustic wave Brillouin scattering in polarization maintaining fibers are investigated theoretically and experimentally. Spectra of polarized and depolarized scattering are measured for two different types of polarization maintaining fibers: the PANDA (polarization maintaining and absorption reducing) fibers and the elliptical-jacket fibers. Calculated results are in agreement with the experimental ones in the low frequency region.     

The research on beat length of polarization maintaining optical fiber with external pressure

Based on the coupled mode equations and elastic optic effect theory, the relationship between polarization maintaining fiber (PMF) beat length and external pressure was analyzed. Moreover, the beat length variation with different external pressure values F as well as angles θ between the pressure direction and PMF's x-axis was calculated numerically. The results demonstrated that the beat length variation was determined both by F and θ simultaneously. When F was a constant, the beat length was changed periodically in π cycle sinusoidal form with θ variation. Then, the minimum and maximum values of beat length would be obtained when θ were even and odd multiples of π/2, respectively. Meanwhile, the beat length variation was linear with F as θ was fixed. In this situation and with F increasing, if θ ∈ (kπ + π/4, kπ + 3π/4) (k ∈ Z), the beat length would increase linearly; otherwise, the beat length variation would be in the opposite direction while θ ∈ (kπ − π/4, kπ + π/4) (k ∈ Z); however, it remained almost unchanged in the case of θ = kπ ± π/4 (k ∈ Z). Finally, the beat length was measured with different pressure values F and angles θ based on a Sagnac interferometer system, and the results shown a great agreement with the theoretical analysis and simulation.     

高性能保偏光纤的关键应用特性研究

开发出一种高性能保偏光纤的制造工艺,并制备出包层直径为80μm的细径高性能保偏光纤。试验表明：该光纤具有优良的全温（-50℃～85℃）偏振串音性能,光纤全温串音变化典型值在3．23dB,具有良好抗弯曲性能和良好的端面研磨性。     

Design of hybrid photonic crystal fiber: Polarization and dispersion properties

A highly birefringent dispersion compensating hybrid photonic crystal fiber is presented. This fiber successfully compensates the chromatic dispersion of standard single mode fiber over E- to L-communication bands. Simulation results reveal that it is possible to obtain a large negative dispersion coefficient of about −1054.4 ps/(nm km) and a relative dispersion slope of 0.0036 nm⁻¹ at the 1550 nm wavelength. The proposed fiber simultaneously provides a high birefringence of order 3.45 × 10⁻² at the 1550 nm. Moreover, it is confirmed that the designed fiber successfully operates as a single mode in the entire band of interest. For practical conditions, the sensitivity of the fibers dispersion properties to a ±2% variation around the optimum values is carefully studied and the nonlinearity of the proposed fiber is also reported and discussed. Such fibers are essential for high speed transmission system as a dispersion compensator, sensing applications, fiber loop mirrors as well as maintaining single polarization, and many nonlinear applications such as four-wave mixing, etc.     

巷道净断面最优尺寸的确定

本文以生产要求和安全间隙为原则,以实现巷道开凿支护费、维修费、通风电力费总现值最小为目标,建立了巷道净断面尺寸设计的数学模型,把该模型引入计算机可完成巷道断面尺寸的最优选择。     

Frequency modulated and polarization maintaining fiber laser with narrow linewidth

A novel configuration of fiber laser with frequency modulation is presented. Frequency modulation, stable polarization state and narrow linewidth are realized by using the waveguide phase modulator, polarization maintaining devices and saturable absorber. It is shown that the laser output reaches 23 mW, linewidth is less than 1 kHz, polarization extinction ratio is higher than 20 dB and maximum value of frequency deviation can reach 7.5 MHz.