Mode measurement of few-mode fibers by mode-frequency mapping.

Since few-mode fibers (FMFs) have great potential as the new transmission media for optical communications, the ability to distinguish different fiber modes is essential. Most of the traditional schemes do not yield phase information, or are limited by beam size and mechanical requirements. Here, a method is presented to analyze the mode distribution of FMFs. The fiber modes are mapped to different frequencies by using dynamic spatial phase masks. The complex amplitudes at these frequencies indicate the amplitudes and phases of the fiber modes. The method can extract not only the amplitude distribution, but also the phase distribution of the fiber modes, and no other assisted light is needed.