2026/07/21 by Sylvain Fautrat
Engineering · Physics and Astronomy · #Geophysics and Sensor Technology #Relativity and Gravitational Theory #Experimental and Theoretical Physics Studies
paper · doi:10.1088/1361-6404/ae8e0d
Abstract An inexpensive interferometer, in which infrared light travels through ordinary telecommunications optical fiber, is described. In one section of the fiber, two waves travel in opposite directions, so that when the device is rotated, it exhibits the Sagnac effect . A digital display allows direct visual observation, and the effect is even visible when the device is slowly rotated in the hands. The theoretical model is developed and requires only basic knowledge of optics (polarized light, birefringent medium) and special relativity (laws of length contraction and time dilation, laws of velocity composition). The article introduces useful higher-level concepts (rotating frame of reference, comoving frames of reference). The calculations are then carried out in a very concrete experimental context. Quantitative observations are clearly in good agreement with relativistic kinematics and not at all with Galilean kinematics. The interferometer at rest also allows the observation of unusual optical effects.