Dissertation > Industrial Technology > Radio electronics, telecommunications technology > Photonics technology,laser technology > Optical waveguide and integrated optics > Fiber optic components

Multimode fiber coupled to a single mode fiber design and research

Author HeJingQiu
Tutor YeYuTang
School University of Electronic Science and Technology
Course Optical Engineering
Keywords multi-mode fiber single-mode fiber self-focusing lens ball lens coupling efficiency
Type Master's thesis
Year 2010
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One of the most important parameters can be got from the instantaneous velocity measure in the detonation and shock wave experiments. For its advantages of non-contact measure and high precision, the technology of speed measurement by the way of laser interference is used more and more widely. Further more, the laser interference velocity measurement system with the all-fiber architecture is leading an important trend in the shock wave and detonation experiments because it has such advantages as compact structure, high precision, a big velocity measurement upper limit. But coupling from multi-mode fiber to single-mode fiber become the most important factor in All Fiber Displacement Interferometer System for Any Reflector. The coupling efficiency will affect the test accuracy.Based on the loss, coupling and some of the basic theoretical research and analysis, the coupling system, system performance and the final data analysis of the Multi-mode fiber to single-mode fiber can be known. Through understanding the development of optical fiber coupling, two kinds, total seven methods of the coupling has been proposed. Analyzed the advantages and disadvantages of various post-coupling method, combination lens method is used to accomplish this multi-mode fiber to single mode fiber coupling system.Firstly, the fiber coupling loss is analyzed which can impact the coupling efficiency. Through the analysis and study on the loss, the loss which is caused by lateral shift is the most important factor. While the loss which is caused by vertical offset and angular offset has little effect. At the same time, the research of the coupling between two single-mode fiber and the research of the output optical beam intensity from the multi-mode fiber can be used to the establishment a model of the coupling system from multi-mode fiber to single-mode fiber.Secondly, through the analysis and research of the self-focusing lens and ball lens, design a prototype coupling system from multi-mode fiber to single-mode fiber. First, the self-focusing lens is used to reduced the beam radius which from the multi-mode fiber optical, then the ball lens is used to reduce the size of the divergence angle which will into the single-mode fiber. Through such a coupling system can greatly enhance the coupling efficiency from multi-mode fiber to single-mode fiber.Finally, the distance from the multimode fiber to the self-focusing lens and the distance from the self-focusing lens to the ball lens can be adjusted to change the system’s coupling efficiency. By the comparison of the data, the best data of the coupling efficiency and the best distance can be gotten.This couple system from multi-mode fiber to single-mode fiber has a compact structure, convenient debugging. And the most important thing is it has a high coupling efficiency. It has a good prospects for the development and practical application. This combination of lenses can be used but it require a high precision, but in the case of the high precision, it will has a very good coupling efficiency. This method for the system has not been seen in home.

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