Single-mode fiber-optic directional couplers

A new design of Y-type end-fused single-mode fiber directional couplers has been suggested and its optimum parameters to obtain losses of 0,5-1 dB have been determined. A technique has been developed for fabricating such couplers by electric arc fusion of single-mode fibers with thin claddings. Excess loss in these couplers splitting into two channels is 1—3 dB and the value is in good agreement with calculations. Cross-talk attenuation between reverse channels exceeds 60 dB, which is an indication of high directivity of the couplers. It has been found by experiments that the developed couplers maintain the state of polarization of the propagating radiation.     

Multichannel data acquisition system for assessing reliability of fiber-optic couplers

With the increased number of fiber-optic couplers in use in network applications, it is imperative that device reliability be ensured. Corning has developed flexible and accurate multichannel test systems for monitoring performance during environmental testing. One such single-mode system using 90 channels has been demonstrated with a one sigma stability of <0.004dB over 136 hours of testing.     

用三干涉臂马赫-曾德尔干涉仪制成的光纤密集型波分复用器

提出一种新型的光纤干涉仪 ,它是采用二个 3× 3单模光纤耦合器组成三光纤系统的马赫 -曾德尔 (Mach- Zehnder)干涉仪 ,当干涉仪的三条光纤干涉臂两两之间分别存在长度差Δ L和2Δ L时 ,干涉仪形成了一个波分复用间隔相等的三波分复用器 ,波分复用的波长间隔仅仅取决于ΔL的大小。实验样品的使用波段为 1.55μm,波长复用间隔为 1.6 nm,附加损耗为 0 .6 d B。     

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。     

Semiconductor waveguide directional couplers for coherent receivers

Optical waveguide 3-dB couplers integrated on semicondutors have been studied, designed and fabricated, using both bulk and diluted multi-quantum-well InGaAsP/InP-based materials, grown by MOCVD. The device structure is based on the two-mode interference (TMI) principle and is fully compatible for integration with the optoelectronic and electronic components of a coherent receiver. Bulk material couplers provide an output balanced within 0.05 dB per nanometer and an excess loss of 1.4 dB, compared to a straight guide, while coupling loss to a tapered-lensed single mode fibre is 4 dB.Improved coupling efficiency to single-mode fibres is achieved by use of moderately diluted multi-quantum-well waveguides, which include InGaAsP wells and InP barriers: coupling loss to a tapered-lensed single-mode fibre as low as 0.5 dB and excess loss of 1.8 dB are featured. Couplers fabricated with this waveguide structure have a balance sensitivity of 0.03 to 0.04 dB per nanometer.A moderately diluted multi-quantum-well 3-dB coupler has been permanently pigtailed and butt-coupled to a dual balanced PIN photoreceiver. This hybrid assembly was tested in a coherent transmission system at 155 and 622 Mbits^-1 showing sensitivities, for 10^-9 BER, of about-38.0 dBm and-28.8 dBm, respectively.     

一种改进的2×2 SOI Mach-Zehnder热光开关

本文设计并制作了基于强限制多模干涉耦合器的2×2 SOI马赫-曾德热光开关.这种光开关采用了深刻蚀结构的多模干涉耦合器和输入/输出波导,较大地提高了干涉耦合器的性能并减少了连接耦合损耗.同时,在调制臂区域采用浅刻蚀结构,保持其单模调制状态.深刻蚀多模干涉耦合器具有优越的特性,在实验中测得不均衡度只有0.03 dB,插入损耗－0.6 dB.基于这种耦合器的新型热光开关,其插入损耗为－6.8 dB,其中包括光纤-波导耦合损耗－4.3 dB,开关时间为6.8 μs.     

Four-wavelength DBR laser array with waveguide couplers fabricated using selective MOVPE growth

We have developed an integrated multiwavelength laser with waveguide couplers using a novel selective metal-organic vapor-phase epitaxy (MOVPE) technique. The lasing wavelength was controlled by modulating the effective refractive index of distributed Bragg reflector (DBR) waveguides. Array lasing wavelengths were distributed from 1548.0 to 1553.5 nm with an average spacing of 1.8 nm. The propagation loss of the waveguide coupler was about 16 dB for inner ports and 20 dB for outer ports with a 6 dB splitting loss. Four-wavelength laser outputs were coupled into a single-mode fibre.     

Design for broadband high-efficiency grating couplers

In this Letter, we propose general optimization methods to design broadband high-efficiency grating couplers for planar waveguides. We attribute the coupling bandwidth to the mismatch of effective indices between the diffracted beam and the actual grating structure around the operation wavelength for fiber to waveguide excitation. The coupling bandwidth formula is deduced. A simple parameter-separate optimization procedure is proposed for general layered grating couplers for high coupling efficiency. Using our principle, we optimized a grating coupler for a horizontal slot waveguide operating at wavelength 1.55 μm for TM polarization. The grating coupler has 1 dB bandwidth of 60 nm and coupling efficiency of 65% with incident light from single-mode optical fiber (SMF) at 8°.     

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.     

Micro-optic devices for fiber-optic communications

A novel approach, “micro-optics”, is proposed to realize coupling/branching in fiber-optic communications. The operation is based on the beam transformation in a graded index rod (beam undulation and beam size change), in association with reflection or refraction at a graded index rod facet. Small-size couplers/dividers have been devised by inserting a semitransparent mirror between the facets of two graded index rods with a length of a quarter of the undulation period. Their best features are small size, simple structure, low insertion loss, and wide application areas. An excess insertion loss as low as 0.5 dB has been realized in a 3-dB divider with SELFOC® rods. As further applications of them, wavelength division multiplexers/demultiplexers have been developed by replacing the semitransparent mirror with a dielectric interference filter. An insertion loss of as low as 1.2 dB and isolation of more than 20 dB for wavelength separation of 20 nm have been realized. Results are also shown on the other type of micro-optic couplers/dividers.     

A Novel Design of Grating Couplers for Efficient Broadband Coupling between Silicon-on-Insulator Nanophotonic Waveguides and Fibres

A novel design of out-of-plane grating couplers is proposed for coupling between silicon-on-insulator nanophotonic waveguides and single-mode fibres. The coupler with the first-order diffraction coupling to the optical fibre is actually a second-order reflected grating with two times of period of the first-order grating. To enhance outcoupled power, a back hole is designed to form in the silicon substrate and a kind of metals is placed on the top acting as a reflection layer. The coupler is optimized using coupled-mode-based simulations, showing that the coupling efficiency to and from tapered optical fibre can be as high as 85% with 1dB bandwidth about 23 nm.     

Multifunctional spectrum-periodic polymer MZI electro-optic switch/filter using serial-cascaded phase-generating couplers: theory, design and analysis

A multifunctional polymer asymmetric Mach-Zehnder interferometer electro-optic switch/filter comprising two serial-cascaded phase-generating couplers and a pair of microstrip electrodes is proposed. Due to the optimization on PGC structure with the given nonlinear least square approximation method, the phase compensation condition and extinction ratio (ER) compensation condition are both realized for achieving periodic frequency response. The ON- and OFF-states voltages are 0 and 8.06 V, respectively. The device has two input ports (A1 and B1) and two output ports (A2 and B2), port A2 contains 10 channels numbered from #?7 to #2, and port B2 contains 9 channels numbered from #?7 to #1. As an optical filter (ON-state), the wavelength space of each channel is within 19.2–21?nm (standard value 20?nm) with the maximum period variation less than 1?nm. The insertion loss for channels #?7 to #2 of port A2 is within 2.69–19.3 dB, and that for channels #?7 to #1 of port B2 is within 2.09–20.2 dB. As an EO switch, the ER of each channel between ON-state and OFF-state for port A2 is more than 15.7 dB, and that for port B2 is more than 12.6 dB. Besides, as required in CWDM networks, the device also exhibits favorable thermal stability under the case of large temperature variation.     

Computer aided design of inverted strip dielectric waveguide millimeter-wave couplers

A computer aided design technique has been developed for the design of a beam splitter coupler and a distributed type coupler using inverted strip dielectric waveguides. The optical beam principle has been used for the beam splitter coupler. Numerical results for these couplers at 80 GHZ with minimum directivity of 30 dB and VSWR of 1.15 have been presented.This work was supported by the Faculty Research Committee of the University of North Dakota under research Grant Number 1813/0909/2369.     

SOI大截面单模脊形X型分支波导的研制

报道了硅片直接键合（ＳＤＢ）ＳＯＩ大截面单模脊形互型分支波导的研制．对于波长为１．３μｍ的光，在θ＝２°小分支角时，这种分支波导的通道串音小于－２０ｄＢ，辐射损耗小于０．３ｄＢ．直通传输损耗小于０．８５ｄＢ／ｃｍ．     

Fiber-Grating-Based Optical Limiting Amplifier Module for Dual-Wavelength, Hybrid Data Rate Transmission

A multichannel fiber-grating-based optical limiting amplifier module is proposed. Dual-wavelength, hybrid data rate transmission is demonstrated with 30 dB input dynamic range. For 5.0 and 2.5 Gbit s dual-channel transmission in a 200 km single-mode fiber, power penalty due to gain competition between channels and backreflection noise is less than 0.6 dB compared to the receiver sensitivity of 0 km, 5.0 Gbit per second single-channel operation.     

Fiber-Grating-Based Optical Limiting Amplifier Module for Dual-Wavelength,Hybrid Data Rate Transmission

A multichannel fiber-grating-based optical limiting amplifier module is proposed. Dual-wavelength, hybrid data rate transmission is demonstrated with 30 dB input dynamic range. For 5.0 and 2.5 Gbit s dual-channel transmission in a 200 km single-mode fiber, power penalty due to gain competition between channels and backreflection noise is less than 0.6 dB compared to the receiver sensitivity of 0 km, 5.0 Gbit per second single-channel operation.     

基于光纤气泡和纤芯失配的Mach-Zehnder干涉液体折射率传感器

介绍了一种基于光纤气泡和纤芯失配的Mach-Zehnder干涉液体折射率传感器. 将两根纤芯经过腐蚀的普通单模光纤熔接在一起, 在熔接点处形成一个气泡, 在距气泡20 mm处级联一段20 mm的细芯光纤, 再接入一段单模光纤, 形成单模光纤-气泡-单模光纤-细芯光纤-单模光纤结构的传感器. 气泡与光纤芯径失配处的两个节点起到光纤耦合器的作用, 从而形成光纤Mach-Zehnder干涉仪. 环境液体折射率的变化,将使得传感器透射谱能量发生变化, 通过测量干涉谱波峰峰值能量从而实现对折射率的测量. 并对所制作传感器的折射率响应特性进行了实验研究, 实验结果表明干涉谱波峰峰值能量与环境液体折射率之间存在良好的线性关系, 当环境液体折射率变化范围在1.351–1.402时, 响应灵敏度为143.537 dB/RIU, 线性度0.996. 该传感器在生物化学领域有较好的应用前景. 关键词： 光纤气泡 纤芯失配 Mach-Zehnder干涉仪 折射率传感     

高性能三端口全光纤开关

提出采用２×２和３×３单模光纤耦合器组合成的马赫－陈德尔干涉仪来制作全光纤开关。解决了在连续熔融拉伸两个耦合器组成马赫－陈德尔干涉仪的过程中，由于干涉的作用而无法监视光功率来控制第二个耦合器的分束比的问题。并且由于是连续熔融拉伸，保证了两条单模光纤干涉臂长度的一致，从而提高了单模光纤马赫－陈德尔干涉仪的性能，使得用其做成的三端口压电陶瓷电控全光纤开关具有宽频带的特性，其最小交调达到３０ｄＢ，附加损耗为０．２３ｄＢ。