Tapered single-mode optical fiber evanescent coupling

We describe the results of a numerical and experimental investigation of how a point source of radiation couples light to the HE ₁₁ mode of a tapered single-mode fiber. Specifically, we have investigated two different geometries of nonadiabatic, tapered single-mode optical fiber. The motivation for this study is the characterization of a single-mode tapered optical fiber biosensor. In such a device light is collected from fluorescent sources located along the cladding surface of the tapered fiber. Taper-to-taper coupling measurements and fiber mode calculations indicate the device sensitivity decreases exponentially as sources are moved away from the tip of the tapered fiber     

单模光纤与单模平面波导端面激励耦合的研究

本文研究了单模光纤与Ti内扩散LiNbO_3单模平面光波导的端面激励耦合问题。测量了它们的场强分布轮廓,给出了两者位置失配影响耦合效率的实验数据。在光纤输出端用光致抗触剂制作一个微透镜,缩小光纤输出的高斯光束束腰尺寸,耦合效率提高了1.47倍,与理论计算值相符。     

Birefringence in single-mode optical fiber due to elliptical core deformation and stress anisotropy

A formula for the difference between propagation constants of two polarization modes caused by elliptical core deformation and stress anisotropy is given for single-mode optical fibers. Birefringence in circular and elliptical core fibers subject to an externally applied uniaxial pressure are measured. Birefringence caused by elliptical core deformation and stress anisotropy are experimentally separated by measuring their wavelength dependences. A value of3.36 times 10^{-10}cm²/gram weight (gw) (=3.43 times 10^{-12}m²/N) is obtained for the stress-optical constant of silica fibers. Residual stress corresponding to external pressure of 240 gw/cm is observed for a fiber with 0.35 core ellipticity.     

耐弯曲单模光纤

本文讨论了光纤弯曲损耗及其主要影响因素,比较了目前采用的改善光纤弯曲损耗各种方法,对照G．652D光纤的特性,分析了两种新型耐弯曲光纤G．657A和B光纤的特性,指出了它们的应用场合。     

SC-type single-mode optical fiber connectors

SC-type single-mode optical fiber connectors specifically developed for subscriber loop networks are discussed. The properties and design of precision zirconia ceramic ferrules which have been found to be ideal for high-performance, low-cost single-mode optical fiber connectors are described. A design approach featuring a plastic-molded rectangular connector housing using a push-pull coupling mechanism which has also been found to be suitable for durable, compact, and low-cost connectors is presented. SC connectors used with 10/125 single-mode fibers exhibit insertion loss of 0.06 dB and return loss of 38.6 dB, with no degradation during and after mechanical and environmental tests. To realize higher packaging density, duplex-ferrule connectors, quadruple-ferrule connectors and optical attenuators have also been developed on the basis of the SC connector design     

Fabrication of single-mode chalcogenide optical fiber

Long lengths (>150 m) of single-mode chalcogenide optical fiber were fabricated by a double crucible technique. Single-mode transmission through 10 m of continuous fiber was demonstrated using an F-center laser at 2.7 μm. The optical loss of this fiber was measured by a standard cutback technique using an FTIR spectrometer and also using an F-center laser, A minimum loss of less than 1 dB/m was obtained     

激光成像系统中高耦合效率单模光纤耦合器设计

在三维激光成像系统中,其性能表现绝大部分决定于器件接收背反射光能幅度的大小,以及耦合器中空间光到光纤纤芯的光耦合效率的高低.为了增加耦合器中激光能量到纤芯内的耦合效率,提出了一种新型非球面透镜到锥形光纤头的耦合器的设计,得到了该耦合器中耦合效率的解析表达式.通过优化耦合透镜的倒相对孔径,对应波长为1 310 nm和1 ...     

Random coupling theory of single-mode optical fibers

A random coupling theory is developed for analyzing the propagation characteristics of the polarization state of light in single-mode optical fibers (including conventional and polarization maintaining fibers) under random disturbances. The basic idea is that the disturbances that a fiber suffers in practice continuously change with time and space, so time-varying coupling will occur along the fiber between two linearly polarized modes HE₁₁ that may propagate in the fiber. A coupled-mode equation of single-mode fibers under random disturbances is derived and solved rigorously with few assumptions. A random coupled-mode equation is derived considering time and space variation. Analytic solutions are obtained and used for analyzing the effect of random birefringence, polarization dispersion, polarization fluctuation, and evolution of the degree of polarization in single-mode fibers and for characterizing fiber properties     

Analysis of the degree of polarization of optical waves in a single-mode optical fiber with random coupling

A single-mode optical fiber model is proposed with discrete mode-coupling centers having random coupling coefficients at regular intervals. The degree of polarization in a single-mode fiber with random-mode coupling does not approach zero with increasing fiber length. Numerical results show that the ensemble average of the degree of polarization approaches a nonzero value the magnitude of which depends on the coupling intensity, the light source spectrum, the fiber birefringence, and the spatial frequency of coupling centers, The theoretical and numerical results clarify the limitation of the perturbation iteration method for long optical fibers.     

多模光纤到单模光纤耦合效率的研究分析

由于多模光纤的纤芯直径远大于单模光纤的纤芯直径,且多模先纤的数值孔径也大于单模光纤的数值孔径,因此多单模转换效率极低.为了提高多模光纤到单模光纤的耦合效率,采用自聚焦透镜对从多模光纤出射的光束进行汇聚,使其半径大小尽量与单模光纤的芯径大小相匹配,然后再利用球透镜来减小被汇聚过的光束的发散角,在不考虑各种连接损耗的前提下,通过ZEMAX来求解多模光纤到单模先纤的耦合效率.采用这种新型组合透镜耦合的方法可以极大提高多单模耦合的耦合效率,其最高耦合效率可达到38.7%.因此,这种组合透镜法是可行的.     

Transmission of a Gaussian pulse in single-mode fiber systems

A formula for the calculation of the transmitted pulse shape through single-mode fiber systems has been derived by using the linear superposition method. It is then applied to the transmission of a Gaussian pulse in the systems with monochromatic, single-mode, and multilongitudinal-mode laser sources. Numerical results are obtained for the various envelopes of multilongitudinal laser spectra. Applicability of the theory to the power spectra of any shape, effects of side modes of a single-mode laser on pulse transmission, and the possibility of developing a technique for obtaining the chromatic dispersion of a fiber are pointed out.     

Flip-chip approach to endfire coupling between single-mode optical fibres and channel waveguides

We report a practical approach to the positioning of a number of single-mode fibres for endfire coupling to channel waveguides. Boivin's approach has been extended to a flip-chip configuration which permits its use with substrates other than silicon.     

高功率啁啾高斯脉冲在光纤中传输的形变研究

从光纤广义非线性薛定谔方程出发,定义了用于衡量脉冲形变大小的脉冲形变因子,定量地分析了在传输过程中脉冲形变因子、临界长度、临界功率及初始啁啾之间的关系。结果表明:在传输过程中,当入射脉冲的峰值功率一定时,正啁啾脉冲的形变比负啁啾脉冲和无啁啾脉冲的形变小;当脉冲的初始啁啾一定时,脉冲传输的临界长度随着传输功率的增加而降低,且随着功率的增大,不同初始啁啾脉冲的临界长度趋于一致;在传输距离一定时,临界功率与初始啁啾呈线性变化,且啁啾的漂移对正啁啾脉冲的临界功率影响较大。     

用腐蚀熔融法制造单模激光二极管与单模光纤相耦合的半球微透镜

近年来由于单模光纤研究的极大成功，促进了单模光纤通信系统和单模光纤应用技术的迅速发展。单模光纤的实际损耗已降到接近理论值，因此为进一步改善单模光纤传输系统的信噪比，提高激     

Raman amplifier model in single-mode optical fiber

Equations to describe the process of Raman amplification in single-mode optical fiber and Stokes and anti-Stokes spontaneous emission generation with conservation of photon number are derived from first principles. The numerical simulation of Stokes and anti-Stokes spontaneous emission is in good agreement with experimental results. The importance of the sometimes-omitted anti-Stokes spontaneous emission terms in wavelength-division-multiplexed situations for optical signal-to-noise ratio is demonstrated by the simulation of light propagation through transmission fiber with and without Raman amplification.     

Efficient self-aligning multibeam coupling into a single-mode fiber

We present and demonstrate a method for efficient coupling of many beams into a single-mode fiber. Using the phase conjugating property for mutually incoherent beams of the double phase conjugate mirror (DPCM), we achieved coupling for a full 6×6 matrix of beams into a single-mode fiber. In principle, this number of input channels can be increased manyfold beyond the 36 used in our experiment. Of the phase conjugate generated by the DPCM in the direction of the fiber, over 97% (Fresnel corrected) entered the fiber, thus giving a highly accurate coupling. The DPCM transmission efficiency itself was measured at 40% (Fresnel corrected), thus giving an overall coupling efficiency of 39%. By optimizing the DPCM parameters, a significantly higher overall coupling could be achieved. An additional advantage of this method is that the DPCM will reconfigure if there are small changes in the system, thus making the system very robust. This multichannel coupling method can be of importance in the coupling of the output beams of a vertical cavity surface emitting laser (VCSEL) into a single-mode fiber where each channel may carry independently modulated information. This technique can be further generalized to a bidirectional multisingle-mode fiber interconnection system, of which a basic 3×2 system is demonstrated     

High-precision characterization of single-mode optical fiber arrays

A precise method of measuring core center dispersion in single-mode fiber arrays is presented. This approach dispenses with the use of high-precision linear translation stages and is based on a direct comparison of the fiber core center position to a simple lithographically patterned template. Combining image recognition and efficient processing algorithm, the fiber-core center positions of fiber arrays can be determined with precision of order of 0.1 /spl mu/m, in both longitudinal and transversal directions. Complementary information about the position of fibers within v-grooves as well as bending of multifiber arrays can be also obtained.     

Polarization fluctuations in a single-mode optical fiber

Polarization fluctuation characteristics of single-mode optical fiber output are examined theoretically and experimentally. A fiber model for studying these characteristics from the perspective of probability on the Poinare sphere is proposed. The relationship of the degree of polarization fluctuation to time and fiber length is shown theoretically. Measurements of submarine and underground cables and long-haul fibers up to 270 km in length generally support the proposed model     

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。     

Mode coupling in angled facet semiconductor optical amplifiers andsuperluminescent diodes

The modal reflectivity of an angled facet has been calculated for index-guided devices when the fundamental mode excites various higher order modes at the facet. The calculations were carried out for waveguide widths ranging from 2 to 20 μm for various lateral index steps and at wavelengths of 834, 1300, and 1550 nm. Plots from these calculations can be used to determine the appropriate facet angles to obtain a given modal reflectivity and optimize the design of optical amplifiers and superluminescent diodes