A rotation angle measurement method based on self-mixing interference (SMI) of a fiber
laser is proposed. The rotation angle can be calculated indirectly by
the displacement measured by SMI. In the experiment, a linear cavity
fiber laser with simple structure and high flexibility is used as the
optical source for measuring the deflection angle. To improve the
measurement accuracy, the SMI signal is filtered by the variational
mode decomposition (VMD) algorithm. The filtered SMI signal is
normalized by Hilbert transform. The even-power algorithm is used to
subdivide the interference fringes, so as to improve the measurement
resolution. The experimental result shows that the measurement error
of angular shift is less than 1% in the range of 10°.