Space Radiation Effect On The Lithium Niobate Phase Modulator For Inter-satellite Optical Communications

Along with the improvement of economic and military forces of our country, Data size between satellites and groud keeps growing. This raises higher request for the speed of communication. In the past twenty years, the optical communication between satellites of our country gets a great achievement. we actualized the the communication between satellite and ground successfully. In front of the booming data size, combining the modern communication technology with the satellite communication is very necessary.We modulate information directly by the source of LD currently, it restricts the speed of communication. Due to this shortage, we propose that external modulator is introduced. Meanwhile, coherent optical communication has an advantage of long-haul transmission which especially fits the none relay environment of space, so phase modulator is chosed. In this dissertation, I mainly study the radiation effect on the loss of the energy of signal. On the research method, the measurement of transmittance and index of refraction which have an effect on the quality of modulation is the first step. Then, the theory of optical waveguide is used to analyze the effect of radiation on modulator.In this paper, I introduce the radiation effect, and give four dose to do the experiment: 5×103rad, 15×103rad, 30×103rad, 80×103rad. I build the radiation model of the changing refractive index of pure Li Nb O3. Simulating it by MATLAB, I gain the refractive index of ordinary light and eccentric light, changing with the dose of radiation.In the experiment, I use the Li Nb O3 crystal produced by Shanghai institute of optics and fine mechanics of Chinese Academy Of Sciences. The test adopts off-line way. Using the continuous test result, I obtain the annealing curve of the Li Nb O3. And by this, I infer the on-line refractive index of it.Base on the inferred refractive index, I analyze the coupler loss of the simple model of modulator. I draw the conclusion that along with the improving of radiation dose, the coupler loss of simple model modulator is reduced.