Science Fair Projects

Doppler Effect and the Fiber Gyroscope


The objective: My project relates to the Doppler Effect and how it is used to measure rotation in a fiber gyroscope. This Doppler effect introduces a frequency shift on a beam that can be measured by using a Sangnac interferometer. I used a turntable as my rotating platform. My rotation speed (measured by number of turns/ second) is my independent variable and the number of fringes shifted is my dependent variable.


I used a HeNe laser to assemble a Sagnac interferometer where two beams propagate in opposite direction on a rotating platform. The interferometer used a long fiber as the beam carrier for the two counter propagating beams to enhance the Doppler effect. A turntable served as the rotating platform. I used a beamsplitter to produce the two beams that were injected into the fiber, and observed the fringe pattern created by the return beams on a screen. We then observed the change in fringe patterns as the spool of fiber rotated on the turntable. We observed the fringe motion at three different rotation speeds corresponding to 17, 33 and 45 rpm.


My hypothesis was correct; we were able to build a basic Fiber Optic Gyroscope and measure the Doppler shift introduced by a rotating platform. We measured the Doppler shift for three rotational speeds of a turntable and the number of fringes observed by the Sagnac interferometer were within 5% of that predicted by theory.


The simple fiber optic gyrsoscope that we assembled was able to measure roataion with surprising accuracy (5%). There were two possible sources of error; the poor contrast ratio of the fringes and the ability to only count the fringe shift with limited accuracy (half a fringe). Reasons for the poor contrast included the use of a non-polarization maintaining fiber and difficulty in balancing the intensities of the two beams. These issues were overcome by doing multiple trials (at least 10) for each rotational speed. This enabled us to reduce the standard deviation to approximately 10% of the average value at the higher speed (45 rpm) and less than 25% of the average value at the lowest speed (17 rpm).

The project measure rotational speeds using the Doppler Shift in a fiber optic gyroscope.

Science Fair Project done By Lara A. Injeyan


Related Projects : Effect of Skyglow on the Visibility of Stars, The Most Efficient Automobile Sunshade, Measurement of True Noon Time Using the Sundial Principle, Saltwater and Sound, Using Solutions' Absorbance Spectra to Predict Their Heating by Light, Safely Thawing Meat Used while Backpacking, How Low Can It Go, Comparison of Thermal Conductivity for Different Metals, Observations of Gas in the Infrared Spectrum, Liquid Light, Liquid Viscosity and Temperature, Study of the Wavelike Properties of Light, Ruben's Tube, The Whispering Gallery Effect, Catch a Wave: Choosing the Right Soundboard, Comparison of the Adhesion of Liquids on Regular Shapes, Stellar Parallax, The Greenhouse Effect, The Study of Alternating Magnetic Fields, Solar Tubes vs. Conventional Fluorescent, Measuring the Speed of Light


<<Back To Topics Page........................................................................................>> Next Topic



Copyright © 2013 through 2015