Source:
https://www.thefoa.org/tech/sciproj.htm
We have gotten many requests for projects involving fibre optic communications for science fairs and K-12 science class projects. We thought we’d share with you the projects we developed for our own kids in the scouts and has been used in classrooms and science fairs. We’ve added a few more advanced exercises to enhance it for older students.
Fibre optics carries signals as pulses of light while copper cables carry signals as pulses of electrons. As the photo below by AT&T from the 1970s showed, one hair-thin fibre can carry more signals than the giant copper telephone cable in the photo. Today’s fibers can carry millions of times the data that that fibre could 40 years ago!
- How Fiber Transmits Signals By Light (Grades K-12)
- The Science Behind Fiber Optics (Grades K-12)
- Transmitting Signals As Pulses Of Light (With Math – Grades 7-12)
- Communications At The Speed Of Light (Grades 7-12)
- Wavelengths Of Light Used In Fiber Optics (Grades 7-12)
How Fiber Transmits Signals By Light (Grades K-12)
This is a demonstration of how communications signals travel as pulses of light over fiber optics, creating a fiber optic telegraph that sends signals as light and can send Morse code. Morse code was the signalling system used by the original telegraph in the middle of the 19th century, creating the first long distance communications.
The project uses plastic optical fiber (POF) which has a large core ( ~1 mm ) and transmits light best at 650 nm, or bright red light so it is easily visible. Regular communications fiber optics uses smaller glass fiber and transmits in the infrared light for greater efficiency. The original project uses a small red LED (available from electronic hobby stores or online) driven by a 9V battery. The diagram was drawn by a 6th grade student who contacted us for help through this web page in 1997, used our idea for his project, then drew the diagram below on his computer. (Yes, that was state of the art computer graphics way back then!)
You can duplicate this demonstration with your own equipment.
You can easily duplicate this experiment with a short length of plastic fiber (samples available from FOA or you can purchase 1mm plastic optical fiber online) and a simple, inexpensive laser pointer. Couple the fiber to the laser pointer (some tape helps increase the fiber diameter to fit snugly into the end of the laser pointer.) Use the switch on the laser pointer to pulse the light on/off to create pulses of light that are transmitted from one end of the fiber to the other.
The laser pointer sends pulses of light through an optical fiber. Look closely (in low lighting like the demonstration above) and you can see the coils of fiber glow with each pulse of light. That glow is caused by the attenuation of the signal in the fiber – you can actually see the loss of the fiber.
If you are doing a science project, below are some background facts that can help explain what is happening.
In the explanation below, we explain some principles of fiber optics and give you some questions to answer. Those questions are in bold type. Answers will be at the end of the page. We also suggest additional activities that can be good for science projects – those comments are in italic type.
See all the classes:
https://www.thefoa.org/tech/sciproj.htm
References:
- Fibre Optics Association
- The Victorian Internet: The Remarkable Story of the Telegraph and the Nineteenth Century’s On-line Pioneers by Tom Standage