Since few-mode fibers 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. In light of the shortcomings of the measurement techniques, it is still desirable to develop a simple method that enables simultaneous measurements of the amplitude and phase distributions of fiber modes.
Several researchers in Wuhan National Lab for Optoelectronics, including Prof. Xinliang Zhang, Prof. Jianji Dong, and Dr. Hailong Zhou, etc. have put forward a method to measure the power and phase distribution of fiber modes in FMFs. The fiber modes are mapped to different frequencies by using dynamic phase masks. We can retrieve the relative amplitude and the relative phase of fiber modes from the frequency content. An experiment is carried out to demonstrate the scheme by using a two-mode FMF. The experimental setup and the evolutionary process of modes are presented in Figs. 1(a) and 1(b). The method can not only extract the amplitude distribution but also the phase distribution of the fiber modes, and no reference light is required, making the system stable and simple.
This work has been on-line published in Optics Letters on 19 March 2018 [1]. Relative work was partially supported by National Natural Science Foundation of China (61622502 and 61475052). Full text can be viewed by
http://ol.osa.org/abstract.cfm?URI=ol-43-7-1435
[1] Zhou H., Zhu Q., Liang W., Zhu G., Xue Y., Chen S., Shen L., Liu M., Dong J., Zhang X. Mode measurement of few-mode fibers by mode-frequency mapping. Optics Letters, 2018, 43 (7): 1435-1438.
Fig.1. (a) Experimental setup for the measurement of fiber mode distribution. (b) The used phase masks and measured patterns.
