| With the rapid development of fiber communication technology, people’s demand for transmission capacity of the communication system has been showing explosive growth. How to achieve large capacity long distance transmission of optical communication technology research in recent years has become a hot spot. However, the higher the transmission rate, the more serious the effects of chromatic dispersion on system, thus solving the problem of the dispersion of high-speed optical communication system is of great significance. Since chirped fiber grating compared to fiber dispersion compensation and electric dispersion compensation multiple advantages, the use of its dispersion compensation is becoming a mainstream technology.Ultra Long fiber grating (length>1m) is capable of excellent dispersion compensation onhuge capacity, ultra high-speed optical fiber communication system But now, although many researchers of ultra long fiber grating fabrication techniques carried out extensive research, it was not produced successfully. The main reason is the focus spot size can not achieve the production of dispersion compensating chirped grating spot size requirements. Many researchers have been looking for technical solutions to solve the too large spot size for point-by-point writing system Point by point writing laser beam focusing problem and the the problem of fiber selection effect on the compensation performance of optical fiber grating have been studied. The topic has great theoretical significance and practical value.The main contents and innovations are as follows:(1) Proposed the use of space-frequency filter for improving optimization excimer laser light source. Design the structure of space-frequency filter. By usingthe converting the optical information means, the space-frequency filter simulation parameters on the long FBG production optimization problem has been analyzed.The intensity distribution of the laser beam changes through space-frequency filter has been studied experimentally and numerically.Finally the excimer laser light source has been successfully improved.(2) The impact of the laser beam after the beam spot size factor and the system has been designed. Using the method of expanded beam to furtherly compress the laser beam divergence angle, and then is the focusing. By comparing the focus between using the collimation system without using collimation, the former has obviously optimization effect. Finally the spot size has been obtained to 0.4μm, and it can be used to write long fiber grating point by point.(3) Firstly studied the laser light intensity distribution near the axis based on the distribution of axis, and eventually got important conclusions about effects of number of Fresnel spherical aberration on spot size. This provides a theoretical basis and guidance for further optimization of the optical system.(4)Studied the effects of optical fiber selection on dispersion compensation performance of fiber grating for the first time. The effect of fiber length, modulation index, core diameter onfiber grating reflection spectrum and delay characteristics has been simulated based on coupled mode theory. At the same time compared the ordinary optical fiber and the W-type grating performance. Optical fiber it self is a cylindrical lens, which can produce secondary focus spot, declining the spot quality. Paper firstly presents a plate glass solution. The analysis shows the solution can solve the problem... |
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