光纤放大器泵浦光高效率注入方式的研究

本文报道了Ｅｒ３＋光纤放大器中，１４８０ｎｍ泵浦光对Ｅｒ３＋光纤高效率注入方式的研究结果。由于采用末端为类球面做透镜的锥形光纤耦合头，使得１４８０ｎｍ泵浦二极管激光器与单模光纤的耦合损耗最低达２．５９ｄＢ，同时耦合头的回波反馈仅为－３４ｄＢ；在Ｅｒ３＋光纤与单模光纤的接续上，采用了热膨胀芯技术，获得了小干０．５ｄＢ的接续损耗。     

Artificial Microwave Volume Holograms Based on Printed Disk Media: Theory and Measurement of Single-Grating Holograms

A new type of complex electromagnetic structure, the artificial microwave volume hologram (AMVH), has been developed. The structure consists of cascaded planar lattices of metallic circular patches with varying size and can be designed to have an effective dielectric modulation that follows a holographic interference pattern. Under the illumination of certain electromagnetic waves, an AMVH can reproduce a required wave field pattern based on its design, just like an optical volume hologram. A theoretical model, namely the self-consistent dynamic-dipole interaction theory, has been presented to characterize AMVHs for wave scattering and beam reconstruction. It can be used for designing and optimizing AMVHs. Comparisons with the coupled-wave theory (CWT) and a full-wave finite element method analysis have been made to validate the proposed theory. A prototype AMVH has been fabricated and measured, which has confirmed the AMVH concept as well as the theoretical model     

空间光通信系统发射光束准直特性研究

提出一种前端直接耦合光纤平凸透镜的聚合物直光锥光准直系统.通过具体地对直光锥的端体结构参数进行优化设计以得到高耦合效率准直精度的直接耦合式聚合物直光准直系统.并利用光线传输理论和仿真实验,论证了直光锥的锥角和锥长准直效能的较大影响.结果表明,选择合适的锥角和锥长能达到十微弧度级准直精度,能较好地满足空间光通信系统远距离发射和接收对于光束质量的要求.此外,理论数值和仿真实验同样验证了该直接耦合式直光准直系统对于较大发散角的发散光束具有较好准直效果.     

Improving the quantum efficiency of erbium-doped fiber laser by using a low-loss tipped fiber splicing process

A tipped single-mode fiber (SMF) structure is employed to reduce the fusion-splicing loss induced at the interface between SMFs and erbium-doped fibers (EDFs). By fusing the EDF and the tipped SMF with lens-like end face at once, the optimized fusion-splicing loss of as low as 0.2/spl sim/0.29 dB is obtained. An improvement on splicing loss of up to 0.46 dB is obtained as compared to the conventional EDF/SMF fusion geometry. The effects of tapered angle and radius of curvature at the end face of tipped fiber on the optimization of fusion-splicing loss are compared. The erbium-doped fiber laser with maximum quantum efficiency of 2.75% is reported by using the proposed splicing technology.     

球聚焦型3×1光纤熔锥耦合器的研究

以线性耦合波方程为基础,采用散射矩阵的方法讨论了等三角分布的熔锥型3×1光纤耦合器,并用射线理论分析了球聚焦透镜光纤的端面效应。将未封装的3×3熔锥光纤耦合器在束腰处切断,并将锥端面熔成聚焦球端,利用光信号在光纤锥形区和球聚焦透镜中特有的传输和耦合特性,实现了光纤的耦合、连接和分束。结果表明:采用该方法耦合效率可达70%左右。同时大大增加了耦合系统的失调容差,降低了调试和封装的难度,因而有着广泛的实际应用价值。     

Radiation Fields of a Tapered Film and a Novel Film-to-Fiber Coupler

Light in a tapered thin-film optical waveguide radiates into the substrate because the waveguide mode in the taper becomes cut off. Our measurement of the radiation pattern shows that the light emerges from the taper as a narrow beam with an angular width of only 2/spl deg/-4/spl deg/. We have studied the problem based on ray optics and based on a wave theory of radiation modes. We also have demonstrated a film-to-fiber coupler in which an optical fiber collects all the light emerging from the taper.     

A band-pass microwave photonic filter based on Lyot-Sagnac filter and cascaded optical structures

A band-pass microwave photonic filter（MPF）based on Lyot-Sagnac filter and two cascaded optical structures is demonstrated.In the experiment,a stabilized and tunable multi-wavelength optical source is obtained by slicing the broadband optical source（BOS）with a Lyot-Sagnac filter.A standard single-mode fiber（SMF）and a fiber ring resonator are cascaded to improve the mainlobe-to-sidelobe suppression ratio（MSSR）and Q-factor of the filter.The analysis shows that MSSR and Q-factor are improved by reducing the split ratio of the coupler or increasing the length of fiber in fiber ring resonator.The results have significant guidance for MPF design by choosing appropriate devices and parameters.Based on the analyses,a band-pass filter with MSSR of 53.54 dB and Q-factor of 4048 is achieved by choosing the split ratio of0.01,the length of SMF of 30 km and the length of fiber in fiber ring resonator of 152.27 cm.     

Highly Symmetric Optical Fiber Tapers Fabricated With a CO2 Laser

This letter presents a simple technique that improves the symmetry of tapered fibers fabricated with a continuous-wave CO₂ laser. The uniform heat distribution inside an optical fiber is achieved by using a nonscanning dual-spot laser beam which applies heat on two sides of the optical fiber simultaneously. In so doing, highly symmetric tapers are obtained with an ellipticity close to unity. These tapers can be used as low-loss and polarization-dependent loss optical fiber filters or other optical devices such as symmetric fibers lenses     

Frozen-in viscoelasticity for novel beam expanders and high-power connectors

Frozen-in viscoelasticity has a significant, yet previously overlooked, impact on the refractive index profile of optical fibers and can serve as the basis for novel fiber devices. Viscoelastic strains can be frozen into an optical fiber during draw, or by cooling down a drawn fiber from high temperature while under tension. The resulting refractive index perturbation can exceed 0.003, exhibits minimal birefringence, and is concentrated in the highest viscosity region of the fiber. We have developed a quantitative theory for the refractive index perturbation, which is in excellent agreement with measured data. We have harnessed frozen-in viscoelasticity to create novel high-performance all-fiber beam expanders achieving mode field diameters in excess of 40 /spl mu/m. These beam expanders are suitable for low-cost high-volume manufacturing and can serve as the basis for high-power single-mode fiber (SMF) connectors, since their lower power density improves reliability during high-power operation. Because of the significant reduction in free-space diffraction associated with the enlarged mode field diameter, these beam expanders may be suitable for MEMS applications, or for coupling between optical fiber terminations and optical fiber sources or detectors.     

一种新型的全光纤超短光脉冲压缩方案

文章提出了一种基于正常色散递减光纤（ND—DDF）、单模光纤（SMF）和非线性环镜（NOLM）组成的全光纤超短脉冲压缩方案。利用光脉冲在正常色散区的色散递减光纤（ND-DDF）中传输时,在脉冲的中心部分将带上较大线性正啁啾（和普通光纤相比）,当脉冲在SMF中传输时色散致啁啾对其进行补偿从而有一个脉冲压缩的过程,最后利用NOLM对压缩后的脉冲进行进一步的压缩和消基座处理。数值模拟的结果表明：半峰全宽为10ps、能量为74pJ的高斯脉冲经过1km的DDF、79m的SMF和20m的NOLM后,可以获得峰值功率为210W,半峰全宽为120fs且几乎无基座的超短脉冲。     

单模光纤拉伸器分布式双折射特性实验研究

在偏振敏感光纤系统中,光纤双折射是重要的参 量。基于压电陶瓷的单模光纤(single-mode fiber,SMF)拉伸器是光纤系统中引入应变、光程或 相位变化等常用的器件,而少有人关注过光纤拉伸器引入的双折射特性。本文提出基于分布 式偏振分析的SMF拉伸器双 折射特性表征方法,结合全穆勒矩阵分析和光频域反射仪技术,可以得到SMF拉伸器缠 绕光纤的分布式双折射特性。实 验得到:在光纤拉伸器使用过程中,光纤双折射随驱动电压增大而增加;当光纤拉伸器缠绕 光纤表面不平整时,可引入更高 的基底双折射,且在施加驱动电压时,基底双折射增加更加明显;设计合适的拉伸机构和光 纤缠绕方法,能有效地避免光纤拉 伸器使用过程中双折射的改变,但可能会引入较强的基底双折射。本文研究结果对于在偏振 敏感光纤系统中使用光纤拉伸器时系统性能的评估及优化具有指导意义。     

大模场面积光纤激光器拉锥法模式选择

大模场面积(LMA)光纤激光器的光束质量通常比单模光纤激光器的光束质量差。采用光纤拉锥的方法进行模式选择,从而提高大模场直径光纤激光器的光束质量。拉锥区距光纤激光器的输出端约5 mm,纤芯最小为9μm,约为未拉锥部分纤芯直径26μm的1/3。实验研究表明,在拉锥后,光纤激光器的光束质量因子M2由3.50减小为1.81,相应的斜率效率由63.6%减小为51.1%。虽然拉锥后最大输出功率减少了约19.8%,但其亮度增大为拉锥前的3倍。     

90° Light Beam Deflection Technology for Single-Mode Optical Interconnection Systems

In this letter, we demonstrate an extremely low loss (<0.06 dB) 1-mm bending radius 90deg light deflection by using a 12-single-mode-fiber ribbon for optical interconnection systems. This technology is easy to be adopted for optical surface mount assemblies that need light beam deflection between the vertical surface-emitting lasers or surface-receiving photodiodes and optical paths parallel to an electric circuit board. We have chosen single-mode fiber (SMF) for the 90deg-bent fiber expecting the single-mode transmission will be applied for high-performance optical interconnection systems because of its wide bandwidth and stability in transmission characteristics. In order to minimize the bending loss and accomplish a small bending radius, we have developed a new optical fiber having higher refractive index of the core (high delta n fiber) than that of conventional fiber and 80-mum-cladding 125-mum spacing 12-fiber ribbon for dense packaging and easy handling in narrow spaces. It is bent at a radius of 1 mm by heating process with a ceramic heater.     

Buried Sol-gel/SiON Waveguide Structure for Passive Alignment to Single-Mode Fiber on Si Substrate

Buried sol-gel/SiON waveguide structure is proposed for efficient optical coupling to single-mode fiber (SMF) using passive alignment technique on silicon substrate. Difficulties of photolithographic patterning on highly nonplanar surfaces were resolved by fabricating the waveguide devices at a distance from the proximity of deep grooves and by using the sol-gel material for producing negative images of the cores in the buried waveguide structure. A good optical coupling between the waveguide and SMF is obtained by bringing the SMF in close contact to the waveguide facet after saw-cutting the SiON cladding away. The loss due to fiber displacement is about 0.6 dB per facet     

Bending effects in biconically tapered single-mode fibers

Biconically tapered single-mode fibers were fabricated, and their characteristics were studied experimentally. The optical throughput was measured as the fiber was being pulled to produce the required radial profile. The tapered single-mode fiber was bent in a simple fixture, and the optical throughput was measured as a function of the bending angle. It is seen that the bending resulted in very strong oscillations of the optical power as the bend angle was varied. At the point when the light in the core was minimal, the cladding region was bright, indicating that the light has moved to the cladding. The propagation characteristics of the tapered single-mode fiber subjected to bending are analyzed using a stepwise approximation. A simple sensor based on this principle is discussed     

基于宽谱光源的光控微波延时技术

提出一种新型的基于宽谱光源和色散器件结合的光控波束形成网络(OCBFN)方案,与利用独立激光器的方案进行了比较,给出了该方案的工作原理和延时链路理论分析,并通过实验验证了该方案实现光控延时的可行性。实验中利用掺铒光纤放大器(EDFA)作为宽谱光源,10 km单模光纤(SMF)作为色散器件实现光路延时,可调谐光滤波器选择光路的工作波长,利用矢量网络分析仪产生微波信号并测量信号延时特性,在9.25~10.25 GHz微波频段中,实验测得的系统延时范围、延时精度及真延时特性(延时大小与微波信号频率无关)验证了基于宽谱光源的可调谐光控微波延时方案的可行性。     

半导体激光器与单模光纤的耦合—理论与实验研究

本文介绍半导体激光器与单模光纤耦合的理论与实验研究.采用拉锥光纤,实验测量的高功率大辐射角半导体激光器与单模光纤之间的耦合效率为44％.     

1.55-μm InGaAsP-InP spot-size-converted (SSC) laser with simpletechnological process

In this letter, we report the realization of a 1.55-μm spot-size-converted (SSC) laser using conventional SCH-MQW active layers and conventional photolithography. The laser consists of a 300-μm-long rectangular gain section, with compensated multiple-quantum-well (MQW) structure, and a 300-μm-long tapered passive waveguide, fabricated on lower SCH layer. The device exhibits a beam divergence of 13°×18° and 3.5-dB coupling loss with a cleaved single-mode fiber (SMF). The 1-dB alignment tolerance is ±2.3 μm in the vertical direction and ±1.9 μm in the lateral direction, respectively     

A study on the development of transmission-type extrinsicFabry-Perot interferometric optical fiber sensor

The conventional reflection-type extrinsic Fabry-Perot interferometric (EFPI) optical fiber sensor has good sensitivity and resolution compared with other types of optical fiber sensors. However, they have the disadvantage that the distinction of strain direction of EFPI is difficult because of measurement method by only fringe counting. This paper presents the newly developed transmission-type EFPI (TEFPI) optical fiber sensor, which has been improved by additional functions, and whose measuring system differs from that of the reflection-type EFPI optical fiber sensors using a single-mode fiber (SMF) and multimode (MMF) fibers as light guides and reflectors, respectively. The output signal of the TEFPI optical fiber sensor was analyzed with the uniform plane wave-based model, the SMF power distribution-based model and the splice loss-based model; the analyzed signals were then verified experimentally. Based on the results of analysis, the TEFPI optical fiber sensor was fabricated using two single-mode fibers connected to the light source and optical receiver; this was then used in strain measurement. The strain measured by the TEFPI optical fiber sensor was compared with that measured by the electric strain gauge     

MEMS可调谐平顶窄带光学滤波器

设计了一种基于MEMS技术的可调谐光学滤波器,它通过光栅将输入的宽带光信号色散展开,以一个MEMS扭镜选择将对应滤波器通带的光信号反射至输出端,从而实现光学滤波和波长调谐功能。滤波器的输入端采用单模光纤,输出端采用多模或者少模光纤,可以实现窄带且平顶的通带特性。经过参数优化,仿真分析得结果显示,采用多模/少摸光纤输出的两种滤波器,其0.5 dB和25 dB带宽分别为0.95 nm/0.29 nm和1.39 nm/0.69 nm,分别满足100 GHz和50 GHz信道间隔的DWDM系统要求。由于输出端采用多模或者少摸光纤,从该滤波器输出的光信号不能继续在单模光纤中传输,只能由光探测器接收,因此该滤波器一般应用于全光网络节点中的下载端口。