Errors introduced by a quarter-wave plate in photoelastic multimode optical fiber sensors

The errors that are introduced by a quarter-wave plate are theoretically evaluated for photoelastic multimode fiber sensors with different configurations. The results indicate that, for the orthogonal and parallel fiber sensors, the error is proportional to the change in the differential retardation of the quarter-wave plate, whereas the error is proportional to the square of the change for the pi/4 fiber sensor.