*1.1.3.4 The Sagnac interferometer (SI)*

The input beam is split into two equal-intensity counter-propagating beams that move along a ring route. The Sagnac effect occurs when the Sagnac interferometer is spun, causing a relative phase change between the beams. The interference spectrum is determined by the setup's angular frequency. Currents, acoustic waves, strain, and temperature can all be monitored using this interferometer [53].
