Font Size: a A A

Study On High-power And High-speed Electro-optic Modulation Technology

Posted on:2012-04-19Degree:DoctorType:Dissertation
Country:ChinaCandidate:W D ZhanFull Text:PDF
GTID:1118330338466060Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
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.
Keywords/Search Tags:electro-optic modulator, space optical communication, demonstration and validation experiment, combined modulator, crosswise traveling wave modulator
PDF Full Text Request
Related items