A method for observing fringe movement in a fibre interferometer

This paper presents an accurate method for observing fringe movement in a Mach-Zehnder type fibre interferometer. We place a photodetector in each of two interference patterns formed by a half-mirror and waves emitted from single-mode fibres. By applying the output voltages of the detectors to X- and Y-terminals of an oscilloscope, we can observe the fringe movement as a rotation of a bright spot along a Lissajous figure.