AbstractAn experiment regarding an inexpensive self‐coupled interferometric fiber optic gyroscope (self‐coupled I‐FOG) is conducted. The gyro output and rotation‐rate resolution of a self‐coupled I‐FOG are investigated and compared with those of a conventional I‐FOG having two couplers. The error effect of rotation output in a self‐coupled I‐FOG due to the interaction of the gyro output and the laser source is examined. Our results show that the resolution of rotation rate of an economical self‐coupled I‐FOG is one order of magnitude lower than that of a conventional I‐FOG. © 1995 John Wiley & Sons, Inc.