1.3μm光学环行器正向损耗及反向隔离比的理论及实验研究

在理论及实验上分析了影响光环行器插入损耗及反向隔离比的因素,讨论了环行器中起、检偏镜参数对其性能的影响.结果表明,起、检偏镜的各组参数存在最佳选择,以保证环行器具有低插损、高隔离比及与偏振无关的特性.作者研制的环行器正向损耗小于1dB,反向隔离比在25.5dB与28dB之间.     

基于二维磁性光子晶体的三端口Y形铁氧体柱环行器

提出一种二维磁性光子晶体缺陷结构,实现了三端口Y形铁氧体柱环行器。采用平面波展开法和有限元方法计算环行器外部特性,计算结果表明:三角晶格二维光子晶体点缺陷微腔谐振频率与相应实验结果一致。在中心频率处,环行器传输效率最高,在输出与输入端口之间几乎没有能量损失;隔离度与插入损耗分别达到23.2dB和0.003 7dB。当偏离中心频率时,传输效率逐渐降低,随频率偏移量增大,环行器传输特性急剧变差。由于所设计的环行器以空气为背景,可克服空气孔结构Y形环行器隔离度低的不足,解决多个铁氧体柱带来的损耗大的问题,因此具有一定意义.     

四端口十字型二维磁性光子晶体环行器

提出一种新的二维磁性光子晶体缺陷结构,并采用该结构使用5个铁氧体柱实现了四端口十字型铁氧体柱环行器。在得到的正方晶格二维光子晶体点缺陷微腔谐振频率与文献中相应的数值结果一致的基础上,采用平面波展开法和有限元方法计算环行器的外部特性。数值结果表明:在中心频率处,环行器隔离度最高达23.49dB,插入损耗最低为0.0281dB;当偏离中心频率时,随着偏移量的增大,环行器的传输性能逐渐变差。设计的环行器的波导内只有一个柱体,从而解决了已有结构中多个柱体带来的插入损耗大的问题。     

倒锥透镜型塑料光纤连接器光学特性研究

提出一种基于倒锥透镜光纤端的新型塑料光纤连接器.为了增大光纤的数值孔径,降低光纤端面对于对准准确度的要求,连接器的光纤连接端面制成倒锥透镜形状.利用截断法对该类型连接器的光学特性进行了测试.1 m长光纤跳线总损耗有75.7％集中在5.4 dB～6.0 dB之间,连接损耗70.7%集中在2.1 dB~2.7 dB之间,同一组跳线插拔200次连接损耗有95％集中分布在2.2 dB～2.58 dB.实验结果表明：倒锥透镜型塑料光纤连接器可以满足“光纤入户”对连接器性能的要求.     

可编程控制的全光磁调谐多路上／下载复用器

研制了一种新型的用于WDM全光网的全光型上/下载复用器，由一对相同的光纤环行器、串接其间的可调谐光纤Bragg光源、WDM复用器和解复用器构成。其中光纤Bragg光栅是用紫外光直写方式在普通单模光纤上制成。讨论了该利用器的工作原理、结构设计、性能和特点。利用磁极间磁场力使光纤光栅产生显著的波长偏移。用可编程磁 极调控光栅的波第偏移。其信道波长调谐速度快，装置无需外加能源即可保持信道波长的偏移。给出了其性能测试结果。信道波长间隔0.8nm，上/下载信道插入损耗1.5dB，通过信道插入损耗2.0dB，上/下端口隔离度30dB，串扰小于-30dB，可调谐信道波长范围6.0nm。其特点是结构简单，可靠。可实现信道波长再利用，从而提高网络的灵活性。     

自放大结构分布反馈光纤激光器输出特性

在光敏性掺铒光纤上制作了45mm长非对称相移结构光纤光栅,构成前后向功率输出比大于100∶1的分布反馈光纤激光器.利用一定长度的掺铒光纤吸收有源相移光栅后的剩余泵浦光,实现了对前向输出激光信号的放大,并采用OptiSystem软件模拟了掺铒光纤长度与增益的关系.为了保持输出激光的窄线宽和低噪音特性,利用布喇格波长与激光相同的光纤光栅和光纤环行器构成光窄带滤波器,对放大后激光信号的ASE噪音进行滤除.研究表明:所设计的激光器结构充分利用了泵浦光,在300mW的(980nm)泵浦功率下获得了功率为32.5mW,线宽为11.5kHz,相对强度噪音为-87dB/Hz的激光输出.     

掺Er光纤飞秒激光器载波包络位相偏移的探测

本文介绍了基于掺Er光纤飞秒激光器光学频率梳中光学部分的研制. 实验上采用重复频率为230 MHz的掺Er光纤飞秒激光器,通过放大、光谱展宽以及单臂f—2f系统,在优化及分析相关参数影响的基础上,获得了~30 dB信噪比f₀的输出,为光纤光学频率梳的建立奠定了基础. 关键词： 掺Er光纤激光器 光学频率计量 光纤光学频率梳 光谱展宽     

剪扭作用下塑料光纤力光转换特性试验研究

为了研究滑开型和撕开型裂缝条件下塑料光纤的光学感知特性,分别进行了剪切和扭转作用下塑料光纤的力光转换特性试验.结果表明,在错动位移由0增加至0.5mm的过程中,光损耗值和菲涅尔反射值与错动位移呈近似线性关系,灵敏度分别达到15.6dB/mm和5.9dB/mm.塑料光纤内部的光损耗特性对剪切作用较敏感,而对扭转作用不敏感,光损耗水平保持在1dB左右.滑开型和撕开型裂缝条件下塑料光纤具有相似的光学感知特性,菲涅尔反射值和光损耗值都可以作为裂缝错动位移的监测指标,其中,光损耗水平变化幅度更大,对裂缝的感知更敏感.     

覆石墨烯微纳光纤双折射与电光调控特性

石墨烯具有特殊的二维柔性结构,可调控费米能级特性和优异的光学、电学性能。利用有限元法,对覆石墨烯微纳光纤光场调控进行理论分析,通过改变石墨烯与缓冲层结构覆微纳光纤的角度,破坏光纤的对称性结构,使光纤具有双折射特性,双折射度大小与石墨烯覆盖角度有关;通过外加电压的方法改变石墨烯的化学势,可对光纤进行开关调控,由此设计出一种包覆石墨烯的微纳光纤电吸收型调制器并进行性能分析。通过数值分析可发现当覆盖光纤角度为270°时,1550nm处双折射度可达1.23×10-3;电吸收调制器工作在1550nm时,器件长度为18μm,消光比为7dB,3dB带宽可达到927 MHz,插入损耗为0.58dB。     

基于210km实地通信链路的高稳定性光学频率信号传递

利用西安和咸阳之间的电信省级骨干光纤网构建了210km的光学频率信号传递测试链路,链路损耗为0.23dB/km。实验中采用可搬运、基于光纤干涉仪、线宽约为200 Hz的激光器作为光源,利用两台低噪声双向掺铒光纤放大器(EDFA)补偿光纤链路损耗和增加光信号的传输距离,放大器平均增益控制在15dB左右,以防止激射。通过测量和分析不同情况下光纤链路的附加相位噪声,可观测到铁路震动引起的规律性干扰。当噪声抑制系统在锁定状态时,链路的相位噪声被抑制了23dB,在剔除铁路干扰时段数据后,获得的210km实地通信链路的秒级频率稳定度达到了1.51×10-14,万秒频率稳定度达到了5×10-17。利用210km通信链路进行了光学频率信号的远程传递测试,分析了限制频率稳定度的主要影响因素,并针对现行光纤布设方式提出了补充要求。该研究为基于通信链路的高精度光学频率信号的传递与比对提供理论支撑。     

A broadband Ka-band microstrip circulator for integrated millimeter wave systems

A Ka-band microstrip circulator, using ferrite with 4 M=5000 G, have been developed. By optimizing the circulator configuration, broadband n=2 Chebyshev response performance are obtained over 7 GHz bandwidth. The circulator have isolation of greater than 15 dB, and insertion loss of less than 1.0 dB.     

Fiber devices using polarization- maintaining fibers

Fiber devices using polarization-maintaining fibers called PANDA fibers are presented. They are polarization-maintaining couplers and polarization-splitting couplers, optical isolators and optical circulators, and multi/demultiplexers designed for 1.3 μm wavelength. Crosstalk of-32 dB and excess loss of 0.03 dB for the polarization-maintaining coupler, and polarization-splitting ratio of 17 dB and excess loss of 0.5 dB for the polarization-splitting coupler have been fabricated by a fusion-elongation method. A fiber polarizer with the extinction ratio of more than 40 dB has been presented by using the difference of bending loss between the orthogonal modes in the PANDA fibers. Multi/demultiplexer with narrow band-pass of 1.4 nm utilizing combination of PANDA fiber polarization dispersion and the polarization-splitting coupler has been realized. An optical isolator consisting of fiber polarizers and a spherical YIG with a lens function and an optical circulator consisting of polarizing-splitting couplers and spherical YIGs have been achieved.     

Fiber devices using polarization- maintaining fibers

Fiber devices using polarization-maintaining fibers called PANDA fibers are presented. They are polarization-maintaining couplers and polarization-splitting couplers, optical isolators and optical circulators, and multi/demultiplexers designed for 1.3 μm wavelength. Crosstalk of-32 dB and excess loss of 0.03 dB for the polarization-maintaining coupler, and polarization-splitting ratio of 17 dB and excess loss of 0.5 dB for the polarization-splitting coupler have been fabricated by a fusion-elongation method. A fiber polarizer with the extinction ratio of more than 40 dB has been presented by using the difference of bending loss between the orthogonal modes in the PANDA fibers. Multi/demultiplexer with narrow band-pass of 1.4 nm utilizing combination of PANDA fiber polarization dispersion and the polarization-splitting coupler has been realized. An optical isolator consisting of fiber polarizers and a spherical YIG with a lens function and an optical circulator consisting of polarizing-splitting couplers and spherical YIGs have been achieved.     

双通道三端口反射式光环行器 结构与特性分析

为了降低广泛应用于光通信系统的光环行器的制造成本和占空比，增强系统中各器件的功能复用，提出一种功能复用反射式光环行器设计方案，利用透镜和反射镜组成光的空间交叉功能来实现功能复用以及光束方向传输引导，从而达到反射式光环行器输入 输出多尾纤之间的对应耦合。利用琼斯矩阵，从理论上对其主要性能进行了分析。分析结果表明，设计的光环行器在功能复用基础上具有低插入损耗、高隔离等特性，达到了光环行器的性能指标，在低插入损耗、高隔离的基础上具有功能复用效用。     

Digitally controlled fault-tolerant multiwavelength programmable fiber-optic attenuator using a two-dimensional digital micromirror device

A digitally controlled multiwavelength variable fiber-optic attenuator using a two-dimensional digital micromirror device (DMD) is introduced. The results from an experimental four-wavelength (i.e., 1546.92, 1548.52, 1550.12, and 1551.72 nm) proof-of-concept attenuator indicate a 26-dB dynamic range and 11-bit resolution. The measured attenuator average coherent optical cross talk per wavelength channel is -38 dB , limited by the additive noise resulting from the nonideal isolation of the optical circulator and the attenuator module. The average optical loss for our experimental attenuator is 15 dB and is limited mainly by the visible-mode DMD that is used as a 1550-nm infrared window device. Our theoretical estimate of a <8-dB loss optimized attenuator can be used for equalization in multiwavelength fiber-optic communications with as many as 108 wavelengths.     

Design and simulation of self-biased circulators in the ultra high frequency band

Theoretical models were developed to design self-biased Y-junction circulators operating at ultra high frequency (UHF). The proposed circulator designs consist of insulating nanowires of yttrium iron garnet (YIG) embedded in high permittivity barium-strontium titanate (BSTO) substrates. A design with as many as 10⁵ or greater wires may be considered in its entirety to determine the electromagnetic scattering S-parameters of a circulator design, thus helping to mitigate the computational limitations of the available finite element method (FEM) tools. The approach seeks to represent the nanowires and the BSTO substrate by an equivalent medium with effective properties inclusive of the average saturation magnetization, dynamic demagnetizing fields, and permittivity. The effective medium approach was validated in comparison with the FEM models. Using the proposed approach, a self-biased junction circulator consisting of YIG nanowires embedded in a BSTO substrate was designed and simulated in which the center frequency insertion loss was calculated to be as low as 0.16 dB with isolation of −42.3 dB at 1 GHz. The 20 dB bandwidth was calculated to be 50 MHz. These results suggest that practical self-biased circulators at the UHF band are feasible.     

Optimized design of multiport optical circulator

This research proposes a practical multiport optical circulator design by using polarizing beam splitter cubes as spatial walk-off polarizers. The use of Porro prisms for directing light requires fewer components and improves space-efficiency. Therefore, a high performance device can be produced at a reduced cost. A six-port optical circulator prototype was fabricated to show the feasibility of the proposed design. The insertion losses range between 0.52 and 1.05 dB, the isolations range between 26.20 and 45.13 dB, and the return losses are 27.72 dB. The benefits of this design's simple and symmetrical structure include cost-efficiency, simple fabrication processes, polarization-independence, the resolve of polarization-mode dispersion issues, and high performance. Additionally, the number of ports can be increased easily.     

A mm-wave four-port quasi-optical circulator

A four-port quasi-optical circulator has been designed, built and tested for operation in the millimetre wave band. The specific circulator reported here was investigated over a 20 GHz bandwidth, centred on 94 GHz. Good performance characteristics were obtained over this bandwidth. Isolations of better than 30 dB and insertion losses of around 0.5 dB were achieved. The input vswr was found to be less than 1.35 over the whole bandwidth investigated and vswr's of less than 1.1 were achieved for narrower bandwidths. It is possible of course to configure the 4-port circulator as a 3-port circulator or indeed as 2-port isolator. Further optimization and consequent improvements in performance are almost certainly obtainable.     

单模光纤1250～1650 nm超平坦宽带耦合器

随着光纤技术的飞速发展和应用．光纤无源器件顺应当前形势也获得很大的发展空间,其中光纤熔锥器件具有制作简单、性能可靠、价格便宜及技术指标优越等优点,从而广受青睐。在熔锥器件中,光纤耦合器是广为应用的基础元器件。目前为实现全光通信。光纤超平坦宽带耦合器则成为热点课题。利用特殊相位补偿工艺方法,研制出单模光纤超平坦宽带耦合器。其工作波长范围为1250～1650nm,3dB带内最大插损偏差小于等于0．4dB,带内最大附加损耗小于等于0．1dB,方向性(输入侧非注人光的一端的输出光功率与注入光功率的比值)大于等于66．5dB,偏振相关性小于等于0．1dB。研制方法有很高的成品率,可批量生产。