摘要
在波分复用系统中，基于平面波导技术制作的阵列波导光栅正起着越来越重要的作用，它提供了一种新的解决通信网络中系统的传输容量和灵活性问题的方案。不过随着波分复用通道数的增加，传统的阵列波导光栅对光源的光谱分布和器件温度漂移不敏感性要求比较高，平坦谱响应的AWG(Arrayed Waveguide Grating)则可以放宽对上述性能的要求。
本文全面介绍了阵列波导光栅波分复用器的基本原理和结构，详细地阐述了AWG的各个性能评价指标，并分析总结了提高这些性能指标的各种方法。为了获得平坦响应的通带宽度，在输入波导末端插入一个多模干涉仪，这样通带宽度得到一定的展宽。不过上述方法往往会导致插入损耗和带通纹波的恶化。本文在此基础上改进多模干涉仪的结构参数，将其设计为抛物线型，通过优化其另一端的宽度和干涉仪的长度，可以减小通带纹波。同时，在多模干涉仪前置一个锥形波导，来对多模干涉仪的输入场进行调整，使其更陡峭，这样也将有助于获得更平坦的带宽。此外，考虑到输入波导弯曲导致的光场峰值偏离波导中心，一细直波导被用来减小由此导致的场型畸变。
按照上述优化过程设计出了一个改进的阵列波导光栅，并采用广角束传播法对其进行了数值计算，改进的AWG的1dB有效带宽可达64％，3dB有效带宽可达78.8％，通道串扰优于-30dB，插入损耗可以维持在-4.35dB到-5.0dB之间。
Arrayed waveguide grating (AWG) is playing an increasingly important role in dense wavelength division multiplexing (DWDM) system. AWG provides a new dimension for solving capacity and flexibility problems in the telecommunication network. However, with the increase of channels, the conventional AWG requires better spectrum of lasers and insensitivity to the wavelength shift, the AWG with flattened passband can broaden these requirements.
In the present thesis, the principle and structure of arrayed waveguide grating are introduced, the characteristic parameters of AWG are expatiated, and some methods that improve these characteristic parameters are analyzed and given. In order to obtain flatten passband, a multimode interferometer (MMI) is used to flatten the bandwidth of AWG and connected at the end of the input waveguide. However it results in larger ripple and deterioration of the on-chip insertion loss of AWG. So the present paper presents the following improved methods. A parabolic shape MMI is applied, and the ripple can be reduced by optimizing the width and length of the parabolic MMI. Moreover, a tapered waveguide is connected before the MMI, which reshapes the input field of MMI and decreases the loss resulting from mismatch of mode fields. Furthermore, a straight waveguide is added before the tapered waveguide to decrease distortion in mode fields, which results from the off centering of the peak field because of the bend of the i
nput waveguides.
According to the solution presented above, a novel AWG is implemented. Wide-angle beam propagation method (BPM) is used to simulate the improved layout. The ldB bandwidth of 64% and 3dB bandwidth of 78.8% are obtained for the 1000GHz channel spacing. Crosstalks to neighboring and all other channels are less than -30dB and the on-chip insertion losses range from -4.35dB to -5.0dB respectively.
引文
[1] J. H. Franz, V. K. Jain, Optical communications components and systems, Beijing: Publishing House of Electronics industry, 2002.4
[2] 徐荣，龚倩．高速宽带光互联网技术．北京：人民邮电出版社，2002．2
[3] 徐荣，龚倩(译)．多波长光网络．北京：人民邮电出版社，2001．4
[4] K. A. McGreer, "Arrayed wavegnide gratings for wavelength routing," IEEE Communications Magazine, 1998, no.12, pp.62-68.
[5] M. K. Smit and Cor van Dam, "PHASAR-based WDM-Devices: Principles, Design and Applications," IEEE J. of Selected Topics in QE, 1996, vol.2, no.2, pp.236-250.
[6] 李艳萍．阵列波导光栅波分复用器的设计、模拟与分析．华中师范大学硕士学位论文，2002．5
[7] P. Munoz, D. Pastor, J. Capmany, "Modeling and designing arrayed waveguide gratings," J. Light. Tech., 2002, vol. 20, no. 4, pp. 661-674.
[8] P. Munoz, D. Pastor, J. Capmany, "Analysis and design of arrayed waveguide gratings with MMI couplers," Opt. Express, 2001, vol.9, no.7, pp. 328-338.
[9] D. Dai, S. Liu, S. He et al., "Optimal design of an MMI coupler for broadening the spectral response of an AWG demultiplexer," J. Light. Tech., 2002, vol 20, no.11, pp.1957-1961.
[10] 方俊鑫，曹庄琪，杨傅子．光波导技术物理基础．上海：上海交通大学出版社，1987．
[11] 叶培大，吴彝尊．光波导技术基本理论．北京：人民邮电出版社，139-154，1981．
[12] 孙飞，刘润民，李国正．有效折射率法的研究．半导体光电，2001，22(1)：34-37．
[13] K. S. Chiang, "Analysis of the effective-index mode for the vector modes of rectangular-core dielectric wavegnides." IEEE Trans. Microwave Theory Tech., 1996, vol.44, no.5, pp.692-700.
[14] K. S. Chiang, C. H. Kwan, and K. M. Lo, "Effective-index method with built-in perturbation correction for the vector modes of rectangular-core optical wavegnides." IEEE J. Lightwave Technol., 1999, vol.17, no.4, pp.716-722.
[15] 严朝军，许政权，陈益新．确定一维单模波导特性的差分波束传播法．上海交通大学学报，1997，31(7)：73-76．
[16] R. Scarmozzino, R. M. Osgood, "Comparison of finite-difference and
fourier-transform solutions of the parabolic wave equation with emphasis on integrated-optics applications." J. Opt. Soc. Am., 1991, vol. 8, no. 5, pp. 724-731.
[17] W. P. Huang, C. L. Xu, W. Lui, and et al, "The perfectly matched layer(PML) boundary condition for the beam propagation method." IEEE Photo. Technol. Lett., 1996, vol. 8, pp.649-651.
[18] D. X. Dai, X. Y. Ao, and Q. C. Zhou, "Cylindrical coordinate wide-angle BPM with PML boundary condition in a bent waveguide." J. Optoelectronics Laser(In Chinese), 2003, vol. 14, pp. 331-335.
[19] 林青春，肖悦娱，何赛灵．基于广角FD-BPM的PML边界处理方法．光子学报，2002，31(2)：349-353．
[20] Y. Hibino, "Arrayed aveguide grating multi/demultiplexers for photonic networks." Circuits &devices, Nov. 2000, pp. 21-27.
[21] 何塞灵，殷源，戴道锌等．硅基底平面波导光通讯集成器件的模拟、设计及工艺．中国计量学院学报，2001，12(2)：65-72．
[22] 周勤存，戴道锌，何塞灵．基于FD-BPM方法的阵列波导光栅模拟．半导体学报，2002，23(12)：1313-1319．
[23] 万莉，吴亚明，王跃林．AWG插入损耗性能的分析和改善．光通信研究，2003，3：56-50．
[24] H. S. Kim, D. K. Han, "Low loss AWG demultiplexer with flat spectral response." USA Patent, G02B6/28, US6188818, 2001-02-13.
[25] 陆思，严瑛白，金国潘等．低插入损耗阵列波导光栅的设计．光子学报，2003，32(7)：769-772．
[26] 李志雄，何对燕，侯睿等．弯曲矩形波导弯曲损耗的计算．光通信研究，2004，2：42-44．
[27] K. Nara, K. Kashihara, T. Nakajima, "Array waveguide diffraction grating." European Patent, G02B6/12, EP1128193, 2001-08-29.
[28] 王文敏，马卫东，陈光等．低插损平坦谱响应阵列波导光栅解复用器优化设计．光子学报，2003，32(9)：1049-1052．
[29] J. Song, D. Q. Pang, S. L. He, "A planar waveguide demultiplexer with a flat passband, sharp transitions an a low chromatic dispersion." Opt. Commun.,227(2003), pp. 89-97.
[30] D. X. Dai, W. Q. Mei, S. L. He, "Using a tapered MMI to flatten the passband of an
AWG." Opt. Commun., 219(2003), pp. 233-239.
[31] C. Dragone, "Efficient techniques for widening the passband of a wavelength router." J. Lightwave Technol., 1998, vol. 16, no. 10, pp. 1895-1906.
[32] K. Okamoto, Y. Ohmori, "Eight-channel flat spectral response arrayed-waveguide multiplexer with asymmetrical Mach-Zehnder filters." IEEE Photon. Technol. Lett., 1996, vol.8, no. 3, pp.373-374.
[33] W. H. Van, "Passband flattening in an arrayed waveguide grating." G02B6/293, WO02103423, 2002-12-27.
[34] K. Okamoto, A. Sugita, "Flat spectral response arrayed-waveguide grating multiplexer with parabolic waveguide horns." Electron. Lett., 1996, vol. 32, no. 18, pp. 1661-1662.
[35] L. Soldono, E. Pennings, "optical multi-mode interference devices based on self-imaging: principles and applications." J. Lightwave Technol., 1995, vol. 13, no. 4, pp. 615-627.
[36] J. B. D. Soole, M. R. Amerfoort, H. P. LeBlanc et al, "Use of multimode interference couplers to broaden the passband of wavelength-dispersive integated WDM filters," IEEE Photon. Technol. Lett. 1996, vol. 8, no. 10, pp. 1340-1342.
[37] M. R. Amersfoort, C. R. Boer, M. K. Smit et al, "Phased-array wavelength demultiplexer with flattened wavelength response." Electron. Lett., 1994, vol. 30, no. 4, pp. 300-302.
[38] M. R. Amersfoort, J. B. D. Soole, H. P. LeBlanc et al, "Passband broadening of integrated arrayed waveguide filters using multimode interference couplers." Electron. Lett., 1996, vol. 32, no. 5, pp. 449-451.
[39] T. kitoh, Y. Inoue, M. Itoh et al, "Low chromatic-dispersion flat-top arrayed waveguide grating filter." Electron. Lett., 2003, vol. 39, no. 15, 1116-1118.
[40] 娄丽芳．平场输出刻蚀衍射光栅波分复用器的设计模拟和器件工艺制作．浙江大学硕士学位论文，2003．2．
[41] 邱海军，刘育梁，李芳等．在解复用模块设计中有效折射率变化的研究．光电子·激光，2003，14(11)：1168-1170．