In this video from the ICT Center, learn about the angles associated with light propagation in optical fibers. Animations and diagrams illustrate the meaning ...
The National Center for Information and Communications Technologies
This media asset was adapted from "ICT Experiment 3: A Simple Fiber Numerical Aperture Measurement".
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Adapted from "ICT Experiment 3: A Simple Fiber Numerical Aperture Measurement" from The National Center for Information and Communications Technologies.
Here are suggested ways to engage students with this video and with activities related to this topic.
- Viewing the video: Use the following suggestions to guide students' viewing of the video:
- Before: Review Snell's law and the conditions under which total internal reflection (TIR) occur. TIR only takes place when the refracted ray bends away from the normal to the surface. How does TIR explain the propagation of light in an optical fiber?
- During: Ask students to pay particular attention to the graphic that defines the acceptance angle of the fiber and the numerical aperture (NA). How is the acceptance angle related to the critical angle inside the fiber?
- After: Review with students some of the concepts that were covered quickly in the video. For example, on what properties of the fiber does the NA depend?
- Doing research projects—individual: The photo of the projected spot of light from the fiber shows many small spots of light. These are due to different modes traveling in the fiber. Ask students to research fiber modes. Where do they come from? How do modes lead to pulse spreading? How can fiber designers create fiber that conducts only one mode (single-mode fiber)?
- Why is the critical angle important to fiber optics?
- Define critical angle in reference to index of refraction.
- Why is the concept of numerical aperture important for understanding fiber optics?
- How is numerical aperture used?