Measuring Vector Modal Content of Vortex Fibers

We present a method based on spatial and spectral (S
²
) imaging technique to measure the vector modal content of vortex fibers. Different vector modes can be told apart and their modal contents can be determined by implementing the S
²
imaging process four times with four different polarizer directions. Moreover, the orbital angular momentum modes (OAMs) can be observed directly through the spiral phase patterns without interference process, and the OAM mode purity can be obtained from the intensity and phase patterns.