密集型多重体全息光栅波长解复用技术研究
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摘要
光纤通信是目前支撑通信业务量迅速增长最重要的技术之一，已成为现代通信的支柱。利用WDM技术则是扩大光纤通信容量、充分挖掘光纤带宽资源的有效手段。然而，迄今为止，作为重要核心器件的解复用器的研究水平却明显低于系统的应用要求。随着WDM系统的迅猛发展，研究更高质量的和更高密集度的WDM器件便显得十分迫切。
本文通过比较几类WDM解复用器件，指出各自的优缺点，并对体全息技术制作解复用器的新方法作了较为深入的研究，并就该器件的设计原理、制作方法、性能特性等一系列问题展开探讨。
利用耦合波理论详细讨论了体全息光栅的衍射效率及角度选择性、波长选择性等衍射属性，阐述光折变多重体全息光栅作为波长滤波器实现波长解复用的基本原理。进一步分析该WDM器件制作过程中诸如记录材料选择、写入光路及曝光时序的确定等关键技术环节。研究表明：Fe：LiNbO_3晶体具有其它光折变材料无法比拟的优点，是用于本系统设计过程中体全息记录的首选材料；均衡考虑，应当选用O光耦合的邻面入射光路作为写入光路。这样的配置具有最高的选择灵敏度、较好的衍射效率均匀性以及相对简洁的系统；考虑到光栅写入时两写入光束之间的耦合，必须根据耦合强度的大小，选择合适的写入光束光强比，才能使写入的光栅具有最高衍射效率。本文不仅通过理论分析得出了最大衍射效率、最佳写入光强比与耦合强度大小的关系表达式，而且设计出用实验手段来确定最佳写入光强比和最大衍射效率的实验方案；为获得尽可能均匀的衍射效率，除了考虑传统的光擦除效应外，更进一步考虑到有效电光系数r_(eff)和空间电荷场E_(sc)与写入光路几何组态的关系，以及各信道衍射光波长、衍射角不同等因素带入的影响，利用递推法，推导出更为精确的曝光时序。
采用高亮度溴钨灯代替价格昂贵的大功率可调谐激光器作为波长解复用试验的光源进行设计，有效降低实验成本，设计出基于体全息技术的16通道波分解复用器的实验方案，并分析该器件的信道容量、噪声特性、插入损耗、隔离度以及存储持久性等主要性能指标。最后指出该项技术实用化进程中尚需解决的若干问题，并对其未来的应用前景予以展望。
Optical fiber communication is one of the most important technologies, which is supporting the rapid growth of communication, and is becoming the prop of modern communication. WDM technology is an effective method to enlarge the capacity of optical fiber communication and to use fully optical fiber bandwidth. However, the properties of WDM devices barely approach the application demand. With the fast development of WDM, it is desired to obtain superior quality and denser WDM device.
In this thesis, by contrasting, I indicate some advantages and disadvantages of several kinds of WDM respectively, and study thoroughly on a new method to make demultiplexing device with volume holographic technology. Meanwhile I discuss some issues about this kind of WDM such as design principal, facture method and its properties.
Properties of volume holographic grating such as diffraction efficiency, angle and wavelength selectivity are discussed in detail based on coupled-mode theory. The fundamental principle that photorefractive volume grating is used as a wave filter for WDM is illustrated. The pacing technology in making the WDM device such as selecting record material, making sure recording geometry and exposure time are analyzed further. The research conclusions are as follows: The Fe doped LiNbO3 should be considered at first as holographic recording material in our system due to its outstanding advantage properties. Compromise consideration, a ordinary-polarization and 90?geometry recording configuration must be applied because such arrangement has the highest selectivity sensitivity, good uniformity of diffraction efficiency and relatively simple system. In order to gain maximum diffraction efficiency, it is necessary to take a suitable beam intensity ratio according to coupling coefficient if the coupling between two wri
ting beams. Not only are the equations of optimum beam ratio and corresponding maximum diffraction efficiency deliberated, but also the experiment scheme to measure them is designed. To gain possible uniform diffraction efficiency, the effects including the relation about recording geometry with effective electro-optical coefficient and space charge field, wavelength of diffraction beam and diffraction angle and so on are taken into account further besides optical erasure, and more perfect exposure time is deliberated based on recurrence method.
Because the expensive tunable laser is not available in laboratory, the high-luminosity halogen lamp is considered as the multiplex photosource, at results, the cost become lower and the program keep more practicable. A experimental scheme of 16 channels wave demultiplex based on volume holographic technology is designed, and its channel capacity, noisiness, cut-in loss, isolation and storage persistence are analyzed. Finally, the application promise of this new technology is anticipated.
本文通过比较几类WDM解复用器件，指出各自的优缺点，并对体全息技术制作解复用器的新方法作了较为深入的研究，并就该器件的设计原理、制作方法、性能特性等一系列问题展开探讨。
利用耦合波理论详细讨论了体全息光栅的衍射效率及角度选择性、波长选择性等衍射属性，阐述光折变多重体全息光栅作为波长滤波器实现波长解复用的基本原理。进一步分析该WDM器件制作过程中诸如记录材料选择、写入光路及曝光时序的确定等关键技术环节。研究表明：Fe：LiNbO_3晶体具有其它光折变材料无法比拟的优点，是用于本系统设计过程中体全息记录的首选材料；均衡考虑，应当选用O光耦合的邻面入射光路作为写入光路。这样的配置具有最高的选择灵敏度、较好的衍射效率均匀性以及相对简洁的系统；考虑到光栅写入时两写入光束之间的耦合，必须根据耦合强度的大小，选择合适的写入光束光强比，才能使写入的光栅具有最高衍射效率。本文不仅通过理论分析得出了最大衍射效率、最佳写入光强比与耦合强度大小的关系表达式，而且设计出用实验手段来确定最佳写入光强比和最大衍射效率的实验方案；为获得尽可能均匀的衍射效率，除了考虑传统的光擦除效应外，更进一步考虑到有效电光系数r_(eff)和空间电荷场E_(sc)与写入光路几何组态的关系，以及各信道衍射光波长、衍射角不同等因素带入的影响，利用递推法，推导出更为精确的曝光时序。
采用高亮度溴钨灯代替价格昂贵的大功率可调谐激光器作为波长解复用试验的光源进行设计，有效降低实验成本，设计出基于体全息技术的16通道波分解复用器的实验方案，并分析该器件的信道容量、噪声特性、插入损耗、隔离度以及存储持久性等主要性能指标。最后指出该项技术实用化进程中尚需解决的若干问题，并对其未来的应用前景予以展望。
Optical fiber communication is one of the most important technologies, which is supporting the rapid growth of communication, and is becoming the prop of modern communication. WDM technology is an effective method to enlarge the capacity of optical fiber communication and to use fully optical fiber bandwidth. However, the properties of WDM devices barely approach the application demand. With the fast development of WDM, it is desired to obtain superior quality and denser WDM device.
In this thesis, by contrasting, I indicate some advantages and disadvantages of several kinds of WDM respectively, and study thoroughly on a new method to make demultiplexing device with volume holographic technology. Meanwhile I discuss some issues about this kind of WDM such as design principal, facture method and its properties.
Properties of volume holographic grating such as diffraction efficiency, angle and wavelength selectivity are discussed in detail based on coupled-mode theory. The fundamental principle that photorefractive volume grating is used as a wave filter for WDM is illustrated. The pacing technology in making the WDM device such as selecting record material, making sure recording geometry and exposure time are analyzed further. The research conclusions are as follows: The Fe doped LiNbO3 should be considered at first as holographic recording material in our system due to its outstanding advantage properties. Compromise consideration, a ordinary-polarization and 90?geometry recording configuration must be applied because such arrangement has the highest selectivity sensitivity, good uniformity of diffraction efficiency and relatively simple system. In order to gain maximum diffraction efficiency, it is necessary to take a suitable beam intensity ratio according to coupling coefficient if the coupling between two wri
ting beams. Not only are the equations of optimum beam ratio and corresponding maximum diffraction efficiency deliberated, but also the experiment scheme to measure them is designed. To gain possible uniform diffraction efficiency, the effects including the relation about recording geometry with effective electro-optical coefficient and space charge field, wavelength of diffraction beam and diffraction angle and so on are taken into account further besides optical erasure, and more perfect exposure time is deliberated based on recurrence method.
Because the expensive tunable laser is not available in laboratory, the high-luminosity halogen lamp is considered as the multiplex photosource, at results, the cost become lower and the program keep more practicable. A experimental scheme of 16 channels wave demultiplex based on volume holographic technology is designed, and its channel capacity, noisiness, cut-in loss, isolation and storage persistence are analyzed. Finally, the application promise of this new technology is anticipated.
引文
[1] 王传林、余重秀、忻向军等，“光的波分复用技术及关键器件的原理和应用”，物理，31(9)，2002．
[2] 张祥冰，“WDM和OTDM系统的技术进展”，光纤与电缆及其应用技术，1997，第4期．
[3] 贾宝华、盛秋琴、董孝义，“用于WDM系统的S-波段光纤放大器的研究”，光电子技术，22(2)，2002．
[4] Kani·J, Jinno·M, "Wideband and flat-gain optical amplification from 1460 to 1510nm by serial combination of a thuliumdoped fluoride fiber amplifier and fiber Ramman amplifier", Electron. Lett. , 35(12), 1999.
[5] 忻向军、余重秀、张茹等，“现代光纤通信中的波分复用技术”，物理，31(9)，2002．
[6] 刘思敏、郭儒、凌振芳，《光折变非线性光学》，中国标准出版社，1992．
[7] Ashkin A, Bord G D, Dziedzie J M, Appl. Phys. Lett. , 1966(9).
[8] Chen F S, Lamacehia J T, Fraser D B, Appl. Phys. Lett. , 1968(13).
[9] 李铭华、杨春晖、徐玉恒，《光折变晶体材料科学导论》，科学出版社，2003．
[10] 陈家壁、苏显渝，《光学信息技术及应用》，高等教育出版社，2002．
[11] H. Kogelnik, Coupled wave theory for thick holograms gratings, The BellSyst. Tech. J. , 1969.
[12] Yang-Tung Huang, "Polarization-selective volume holograms: general design", Appl. Opt. , 33(11), 1994.
[13] S·Breer, K·Buse, "Wavelength demultiplering with volume phase holograms in photorefractive lithium niobate ", Appl. Phys. B, 66, 339-345, 1998.
[14] J·W·An, N·Kim, K·W·Lee, "Volume holographic wavelength demultiplexer based on rotation multiplexing in the 90°geometry", Opt. Commun. , 197: 247-254, 2001.
[15] 陶世荃等，《光全息存储》，北京工业大学出版社，1998．12．
[16] 李晓春，“晶体大容量体全息数据存储”，清华大学工学博士学位论文，1998．
[17] F. H. Mok, G. W. Burr, D. Psaltis . Opt. Lett. , 1996, 21(12).
[18] Hanying Zhou, Feng Zhao, Francis T. S. Yu, Angle-dependent diffraction efficiency in a thick photorefractive hologram, Applied Optics, 1995(34).
[19] P·Gunter and J·P·Huignard, Photorefactive Materials and Their Applications, Springer-Veriag,
New York, 1998, Chap. 2, p. 60.
[20] Fainman·Y, Klancnik·E, Lee·S·H, "Optical coherent image amplification by tow-wave coupling in protorefractive BaTiO_3", Optical Engineering, 25(2): 228-234, 1986.
[21] L·Z·Cai, P·Yeh, H·K·Liu, "Mean fringe contrast, optimum beam ratio and maximum diffraction efficiency for rolume gratings written by coupled waves", Optics communications, 132, 1996.
[22] L·Solymar, in: Electrooptic and Photorefractive Materials, Ed. P. Gunter, Springer, Berlin, 1987.
[23] D·Psaltis, F·Mod, and H·S·Li, Nonvolatile storage in photorefractive crystals, Opt. Lett. 19, 1994.
[24] 忽满利、刘玉华、刘继芳等，“光折变晶体均匀多重全息图存储研究”，光子学报，28(7)，1999．
[25] E·C·Maniloff and K·M·Johnson, Maximized photorefractive hologram storage, Appl. Phys. , 70(49), 1991.
[26] Kasra Rastani, "storage capacity and cross-talk in angularly multiplexed holograms: two case studies", Appl. Opt. , 32(20), 1993.
[27] Andersen P E, Marrakchi A, Noise-free holographic storage in iron-doped lithium niobate crystals, Opt. Lett. , 19(19), 1994.
[28] Joseph J, Pillai P K C, Singh K, "Anovel way of noise reduction in image amplificatio by two-beam coupling in photorefractive BaTiO_3 crystal", Opt. Comm. , 1(80), 1990.
[29] 闫晓娜、刘立人，“铌酸锂晶体光感应散射与外加电场的关系”，光学学报，19(11)，1999．
[30] Amodei J J, Phillips W, Staebler D L, "Improved electrooptic materials and fixing technology for holographic recording", Appl. Opt. , 11(2), 1972.
[31] 忽满利、李育林、乔学光等，“低噪音光折变体全息存储”，光子学报，27(7)，1998．
[32] 张明德、孙小菡，《光纤通信系统与原理》(第2版)，东南大学出版社，2001．6．
[33] 孟纲，“多重全息图热固定的研究”北京工业大学硕士学位论文，2001．
[34] M·Carrascosa and F·Agullo-Lopez, "Theoretical modeling of the fixing and developing holographic gratings in LiNbO_3 "Opt. Soc. Am. . B, 7(12), 1990.
[35] L·Arizmendi, P·D·Townnsendt, M·Carrascosa, "Photorefractive fixing and related thermal effects in LiNbO_3", Phys: Condens. Matter, 3, 1991.
[36] 张心正，“光折变体全息高密度光存储器及其应用”，南开大学博士学位论文，2001．4．
[37] D·von der Linde, et al. , "Multiphoton photorefractive processes for optical storage in LiNbO_3",
Appl. Phys. Lett. , 1974, 25(3).
[38] Y·S·Bai, R·R·Neurgaonkar, and R·Kachru, "Resonant two-photon photorefraction grating in praseodymium-doped strontium barium niobate with CW lasers", Opt. Lett. , 1996, 21.
[39] R·McRuer, et al. , "Two-wavelength photorefractive dynamic optical interconnect", Opt. Lett. , 1989, 14(21).
[40] H·C·Kulich, "Transfer function for image formation of objects reconstructed from volume holograms with different wavelengths", Apl. Opt. , 1992, 31(14).
[41] C·Alves, et al. , "Refreshed photorefractive buffer memory for permanent readout ", Optical Materials, 1995, 4(1).
[42] J·P·Drolet, et al. , " Compact integrated dynamic holographic memory with refreshed holograms", Opt. Lett. , 1997, 22(8).
[43] 张成良、韦乐平，“WDM技木的现状与发展趋势”，电信科学，9，1998．
[44] 胡台光，“波分复用器件现状”，光通信技术，24(2)，1999．
[2] 张祥冰，“WDM和OTDM系统的技术进展”，光纤与电缆及其应用技术，1997，第4期．
[3] 贾宝华、盛秋琴、董孝义，“用于WDM系统的S-波段光纤放大器的研究”，光电子技术，22(2)，2002．
[4] Kani·J, Jinno·M, "Wideband and flat-gain optical amplification from 1460 to 1510nm by serial combination of a thuliumdoped fluoride fiber amplifier and fiber Ramman amplifier", Electron. Lett. , 35(12), 1999.
[5] 忻向军、余重秀、张茹等，“现代光纤通信中的波分复用技术”，物理，31(9)，2002．
[6] 刘思敏、郭儒、凌振芳，《光折变非线性光学》，中国标准出版社，1992．
[7] Ashkin A, Bord G D, Dziedzie J M, Appl. Phys. Lett. , 1966(9).
[8] Chen F S, Lamacehia J T, Fraser D B, Appl. Phys. Lett. , 1968(13).
[9] 李铭华、杨春晖、徐玉恒，《光折变晶体材料科学导论》，科学出版社，2003．
[10] 陈家壁、苏显渝，《光学信息技术及应用》，高等教育出版社，2002．
[11] H. Kogelnik, Coupled wave theory for thick holograms gratings, The BellSyst. Tech. J. , 1969.
[12] Yang-Tung Huang, "Polarization-selective volume holograms: general design", Appl. Opt. , 33(11), 1994.
[13] S·Breer, K·Buse, "Wavelength demultiplering with volume phase holograms in photorefractive lithium niobate ", Appl. Phys. B, 66, 339-345, 1998.
[14] J·W·An, N·Kim, K·W·Lee, "Volume holographic wavelength demultiplexer based on rotation multiplexing in the 90°geometry", Opt. Commun. , 197: 247-254, 2001.
[15] 陶世荃等，《光全息存储》，北京工业大学出版社，1998．12．
[16] 李晓春，“晶体大容量体全息数据存储”，清华大学工学博士学位论文，1998．
[17] F. H. Mok, G. W. Burr, D. Psaltis . Opt. Lett. , 1996, 21(12).
[18] Hanying Zhou, Feng Zhao, Francis T. S. Yu, Angle-dependent diffraction efficiency in a thick photorefractive hologram, Applied Optics, 1995(34).
[19] P·Gunter and J·P·Huignard, Photorefactive Materials and Their Applications, Springer-Veriag,
New York, 1998, Chap. 2, p. 60.
[20] Fainman·Y, Klancnik·E, Lee·S·H, "Optical coherent image amplification by tow-wave coupling in protorefractive BaTiO_3", Optical Engineering, 25(2): 228-234, 1986.
[21] L·Z·Cai, P·Yeh, H·K·Liu, "Mean fringe contrast, optimum beam ratio and maximum diffraction efficiency for rolume gratings written by coupled waves", Optics communications, 132, 1996.
[22] L·Solymar, in: Electrooptic and Photorefractive Materials, Ed. P. Gunter, Springer, Berlin, 1987.
[23] D·Psaltis, F·Mod, and H·S·Li, Nonvolatile storage in photorefractive crystals, Opt. Lett. 19, 1994.
[24] 忽满利、刘玉华、刘继芳等，“光折变晶体均匀多重全息图存储研究”，光子学报，28(7)，1999．
[25] E·C·Maniloff and K·M·Johnson, Maximized photorefractive hologram storage, Appl. Phys. , 70(49), 1991.
[26] Kasra Rastani, "storage capacity and cross-talk in angularly multiplexed holograms: two case studies", Appl. Opt. , 32(20), 1993.
[27] Andersen P E, Marrakchi A, Noise-free holographic storage in iron-doped lithium niobate crystals, Opt. Lett. , 19(19), 1994.
[28] Joseph J, Pillai P K C, Singh K, "Anovel way of noise reduction in image amplificatio by two-beam coupling in photorefractive BaTiO_3 crystal", Opt. Comm. , 1(80), 1990.
[29] 闫晓娜、刘立人，“铌酸锂晶体光感应散射与外加电场的关系”，光学学报，19(11)，1999．
[30] Amodei J J, Phillips W, Staebler D L, "Improved electrooptic materials and fixing technology for holographic recording", Appl. Opt. , 11(2), 1972.
[31] 忽满利、李育林、乔学光等，“低噪音光折变体全息存储”，光子学报，27(7)，1998．
[32] 张明德、孙小菡，《光纤通信系统与原理》(第2版)，东南大学出版社，2001．6．
[33] 孟纲，“多重全息图热固定的研究”北京工业大学硕士学位论文，2001．
[34] M·Carrascosa and F·Agullo-Lopez, "Theoretical modeling of the fixing and developing holographic gratings in LiNbO_3 "Opt. Soc. Am. . B, 7(12), 1990.
[35] L·Arizmendi, P·D·Townnsendt, M·Carrascosa, "Photorefractive fixing and related thermal effects in LiNbO_3", Phys: Condens. Matter, 3, 1991.
[36] 张心正，“光折变体全息高密度光存储器及其应用”，南开大学博士学位论文，2001．4．
[37] D·von der Linde, et al. , "Multiphoton photorefractive processes for optical storage in LiNbO_3",
Appl. Phys. Lett. , 1974, 25(3).
[38] Y·S·Bai, R·R·Neurgaonkar, and R·Kachru, "Resonant two-photon photorefraction grating in praseodymium-doped strontium barium niobate with CW lasers", Opt. Lett. , 1996, 21.
[39] R·McRuer, et al. , "Two-wavelength photorefractive dynamic optical interconnect", Opt. Lett. , 1989, 14(21).
[40] H·C·Kulich, "Transfer function for image formation of objects reconstructed from volume holograms with different wavelengths", Apl. Opt. , 1992, 31(14).
[41] C·Alves, et al. , "Refreshed photorefractive buffer memory for permanent readout ", Optical Materials, 1995, 4(1).
[42] J·P·Drolet, et al. , " Compact integrated dynamic holographic memory with refreshed holograms", Opt. Lett. , 1997, 22(8).
[43] 张成良、韦乐平，“WDM技木的现状与发展趋势”，电信科学，9，1998．
[44] 胡台光，“波分复用器件现状”，光通信技术，24(2)，1999．