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lab1 - ECE 4370 Lab 1 Introduction This lab was designed to...

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ECE 4370 Lab 1 Introduction This lab was designed to give students valuable experience working with the equipment in the optics lab. This was accomplished through two simple experiments. The first requirement was to investigate the numerical aperture of three different types of optical fiber. As will be explained, this was measured by analyzing the cone of light projected from the end of an optically excited fiber. The second part of this lab was to measure the numerical aperture of a glass slide. This was accomplished by determining the maximum angle at which the slide will accept light. Experiment 1 N.A. measurement of optical fibers Preparation To prepare for this part of the lab, we must first establish the scope of the experiment, which in this case, is to measure the N.A. of three different classes of optical fiber. We also realize that by using the principles of optics established in the course that measurement of N.A., can indeed by accomplished by measuring the cone of light projected from a fiber. This will be discussed in further detail in the analysis section. Procedure In order to accomplish this measurement, we first prepared the fiber by stripping, cleaving, and cleaning both ends. It is critical that these steps be taken. If either end of the fiber is cut at an angle, our results for N.A. will be inaccurate. Therefore, we must use the fiber cleaver in order to ensure a nearly vertical cut. A snapshot of this part of the procedure is shown below. Figure 1- Once the fiber has been cleaved, the next step is to couple laser light into it and project this light onto the target. In order to do this, we make use of the equipment shown in the snapshot below.
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Figure 2- After carefully placing both ends of the fiber into their respective holders, we placed these holders in chucks adjacent to the laser and target. By manipulating the fiber chuck adjacent to the laser, we adjusted the position in three dimensions in order to couple the maximum amount of light into the optical waveguide. The quality of the coupling was easily observed by noting the intensity of the light projected onto the target. Once the chuck was adjusted to give the maximum optical coupling, we could then examine the optical pattern on the target. A picture of the laser-fiber-holder is shown below. Figure 3- Now that the laser light was strongly coupled to the optical fiber, we positioned the output side of the fiber in such a way that the light was centered on the “bull’s-eye” on the target center. Once this was accomplished, we moved the target to 4-5 different distances, and obtained measurements. We recorded the radius of the circle on the target as a function of distance from the fiber output.
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