【作者】 詹伟达；

【导师】 王志坚；

【作者基本信息】 长春理工大学 ， 光学工程， 2011， 博士

【摘要】 电光调制技术是以一些晶体的电光效应为物理基础,对光的相应参数进行调变的技术,其主要应用于光通信、光刻和激光雷达等领域。在空间光通信中,一般都采用激光作为信息传输的手段,大功率、高速率电光调制技术是空间光通信领域的重要研究内容,已成为制约我国空间光通信研究和发展的瓶颈之一。目前,世界各科技强国都十分重视空间光通信的特殊的军事应用价值,先后开展了空间光通信及其关键技术的研究工作,并将其提升到了较高的战略地位。光通信可分为光纤通信和空间光通信两大类,二者对电光调制的原理、实现方法、参数指标等的要求都不尽相同。目前,高速率电光调制技术已经较早并广泛地应用于光纤通信领域中,发展非常迅速。高速率电光调制器主要针对1550nm波段激光、采用集成波导调制方式、实现调制带宽可以达到160GHz以上,通信速率为40Gbps的光纤通信系统已经商业化。在自由空间、临近空间、深空等链路的空间激光通信中,我国的大功率电光调制技术研究相对滞后。空间光通信采用的激光主要为800nm波段,此波段的激光在大气信道中传输时具有“透明”特性。但空间激光通信的链路距离非常远,激光在大气信道中的传输损耗很大,所以需要电光调制器的输出光功率在几百mw或几W的数量级,这是光纤通信中的高速电光调制器件无法实现的。为保证大容量信息传输需要,空间激光通信电光调制器必须折中考虑功率和速率两个指标,调制速率一般要求在几百Mbps到几Gbps之间。目前,课题组共开展了两个方法的研究。一种方法是采用大功率、高速率电光调制技术直接调制能满足空间激光通信需要的电光调制器,主要针对800nm波段,考虑此波段的光学器件较多、技术相对成熟和大气的低损耗特性,这方面的工作和本论文研究在“十一·五”末期已经取得了阶段性的成果,调制速率为100Mbps～500Mbps、最大光功率输出大于0.5W的电光调制器(采用外调制方式)已经成功应用于空间激光通信实验中。方法二是利用光纤通信中现有的高速率调制技术,针对光纤低损耗的1550nm波段,开展后续的光放大技术的研究,力争研制出满足较远距离的临近空间或深空激光通信需要的大功率、高速率集成激光发射模块,这方面的研究预计在“十二·五”中期能够取得突破。本论文根据研究方法一,提出了七个需要解决的问题：(1)如何提高光功率输出和调制速率；(2)如何降低半波电压；(3)如何设计和制作电极；(4)如何为调制器提供驱动信号；(5)如何实现静态工作点自动控制；(6)如何设计工程样机；(7)如何开展测试和应用实验。为解决上述问题,本文主要研究工作分解为如下几个方面：(1)深入调研国内外研究现状,分析和总结现有研究成果；(2)为提高电光调制的输出光功率,选择了脉冲编码调制、强度调制、横向调制和体调制等具体调制方式,相对波导集成调制方式比较容易实现、不需要非常苛刻的波导设计工艺；(3)为提高电光调制的输出光功率,考虑了晶体的抗光损伤能力,折中考虑了晶体尺寸、长宽比和通光孔径,设计了高效的光路结构,设计了长光程自聚焦透镜,实现了准直器和光纤的高效耦合；(4)为提高调制速率和有效降低半波电压,对铌酸锂晶体的结构和特性进行了详细分析,提出了双晶串联的组合调制和横向行波调制方式；(5)开展了行波电极的设计、制作工艺和流程等研究；(6)电光调制器的驱动信号已经进行了射频频段,为此开展了基于现有射频集成放大器件的二级负反馈放大技术研究；(7)为了克服温度、折射率变化等影响,开展了静态工作点自动控制、温度控制、频率稳定等研究；(8)在工程样机设计方面：开展了晶体尺寸、起偏器和检偏器参数、自聚焦透镜、光路结构、电极、机械结构、小型化等研究；(9)在室内：主要开展了波长、光功率和调制带宽等的测试,并开展了数字信号传输实验；(10)在野外：主要开展了光功率预算、功率损耗、通信速率和误码率等研究和测试,分析了实验验证效果。本论文开展了大功率、高速率电光调制技术的理论分析、仿真研究、工程样机设计和应用实验研究,实验数据对理论研究具有较好的支撑和验证作用。随着我国“十二·五”期间月球探测、空间站、载人航天、深空探测等领域的规划和发展,激光技术、光通信技术、光电子技术等方面的研究将会不断深入。大功率、高速率电光调制技术的研究及成果将对未来空间光通信的应用和发展起到一定的促进作用。更多还原

【Abstract】 Electro-optic modulation technology, which is based on the electrooptic effect produced by some crystals, is the technology of modulating to the parameter of light, and mainly applied in the fields of optical communication, lithography laser radar, and so on. In the field of space optical communication, laser is usually used as the main means of transmitting information. However, high-power and high-speed electro-optic modulation technology, as the important research branches of space optical communication, is one of the hard nuts to crack in the study and development of space optical communication in our country. At present, all of the powerful countries in scientific research advance in the world attach importance to the special values of the space optical communication in the military affairs, gradually do the research of the space optical communication and the related technology, and promote it to a high strategic position.Optical communication can be divided to the fiber-optical communication and space optical communication, which differ in the electro-modulate principle, realizing methods, and parameters etc. Presently, high-speed electro-optic modulation technology widely used in the fiber-optical communication, and develops fast. High-speed Electro-optic modulator mainly use waveguide modulation to modulate 1550nm wave laser, the achieved modulate bandwidth can be more than 160GHz, and fiber-optical communication system of 40Gbps has been commercialized. In the field of space laser communication of the link space such as freedom space, near space and deep space, our study of Electro-optic modulation technology is behind other countries relatively. Space optical communication mainly uses 800nm laser because of its transparent feature in the air transmission. But the link distance is far in the space laser communication, and the transmission loss of laser is big in the air and water channel, so the out optical power of Electro-optic modulator need order of magnitude of hundreds of mW or even W, which can not be accomplished by using the waveguide Electro-optic modulator in the fiber-optical communication. To meet the needs of large transfer information, Electro-optic modulator must take the two indicators, power and rate account, and compromise them to make the modulate rate meet the requirements between hundreds of Mbps and several Gbps.At present, the discussion group has developed two main studies in laser emission technology. The first study is to manufacture the Electro-optic modulator which can satisfy the space laser communication by directly using the high-power and high-speed Electro-optic modulation technology, mainly applying it in the wavelength of 800nm, which has more optical elements, much proven techniques and low-loss feature of air in this wavelength. The above study and the related thesis have got the staged achievement in the end of "Eleventh Five-Year Plan". The electro-optical modulator with modulate rate of 100Mbps～500Mbps, the biggest optical power output of which is more than 0.5W, has already been applied in the demo experiment of space laser communication successfully. The second study, aiming at the low-loss fiber wavelength of 1550nm, is to take advantage of the existing high-speed modulation technology to carry out the study of optical amplitude technology, develop the high power and high-speed integrated laser emission element to satisfy the far distance near space or deep space laser communication. We hope this study will get breakthrough during the "Twelve Five-Year Plan"The paper is based on the application of 800nm wavelength space laser communication. With the combination of scientific research, the paper makes the theoretical analysis and simulation study of high-power, high-speed electro-optical modulation technology, also designs the engineering prototype, and does some application experimental study, gives the experimental data support and proves the theoretical study. In this paper, seven problems are put forward:(1) How to improve the optical output power and modulate rate; (2) How to reduce half-wave voltage; (3) How to design and make electrode; (4) How to provide the drive signal for modulator; (5) How to achieve auto control of quiescent point; (6) How to design engineering prototype; (7) How to carry out tests and application experiments.To solve of the above problems, this paper divides the research into the following parts: (1) To make survey of current domestic and world situation, analyze and conclude existing study result carefully; (2) To improve the output optical power of the Electro-optic modulator, select the specific modulate mode of pulse code modulation, intensify modulation, crosswise modulation and body modulation, which is simpler, more easily realized than waveguide modulation, and does not need high level waveguide design technology; (3) To improve the output optical power of modulator, and design the high efficient optical paths structure, self-focusing lens, realize coupling of collimator and fiber, synthesize the resisting optical harm ability of crystal, splittly the difference of size, length-width ratio and clear aperture; (4) To improve modulate rate and reducing half-wave voltage, analyzing the structure and feature of Lithium Notate crystal, and proposing double crystal series-wound group modulation and crosswise traveling wave modulation mode; (5) Carrying out the design of traveling wave electrode, workmanship, and flow etc; (6) Due to the fact that the drive signal of Electro-optic modulator already run into the radio frequency range, hence launching the study of two level feed back amplitude technology based on existing radio frequency integrated amplitude elements; (7) To overcome the effect of temperature, refractive index variation, carrying out the study of quiescent point, automatic control, temperature control, frequency stabilization; (8) In the aspect of engineering prototype design, carrying out the study of size, polarizer, analyzer self-condenser lens, light path architecture, electrode, physical construction, miniaturization; (9) Indoors:mainly testing the wavelength, optical power and modulate bandwidth, and doing some signal transfer experiment; (10) Outdoors:mainly studying and testing the budget of optical power, power loss, communication rate, error rate, etc, analysis the experimental checking effect.This paper carries out theoretical analysis, simulation, engineering design and application of experimental research about the high-power, high-speed electro-optic modulation techniques, the experimental data supporting theoretical research. Along with the development of space scientific exploration, moon detection, space station, deep space detection during the "Twelve Five-Year Plan" in China, laser technology, optical communication technology and photo electronic technology will be furthered. The research and achievement on high-power and high-speed electro-optical modulation technology will promote development of space optical communication.更多还原