Nu Yu


February 1987

Document Type


Degree Name



Dept. of Electrical Engineering


Oregon Graduate Center


The efficient coupling between a semiconductor laser and a single-mode fiber is a key element for fully utilizing the single-mode fiber for the optical communication. In this thesis, the Gaussian beam approach is used for analyzing the coupling of a single-mode laser diode to a single-mode optical fiber by a microlens. Two analytical methods based on both the ABCD law and the diffraction theory are presented. The effect of a microlens on both the phase and amplitude of a Gaussian beam are discussed in detail. The presented analysis specifies the optimum coupling in terms of laser and fiber parameters and the laser to fiber distance. Furthermore, the coupling efficiencies achievable in hemispheric and etched conical microlenses systems are explicitly compared. The present analysis shows that a coupling efficiency as high as 62% is achievable with the optimal choice of laser and fiber parameters. Additionally, theoretically obtained coupling efficiency is compared with the experimental data for both butt and etched fibers.





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