Research on mode division multiplexer with graded-index distribution,low loss and low crosstalk

A graded-index mode division multiplexer with low loss and low crosstalk is proposed. The transmission channel adopts a pure silica core with large effective area to achieve low attenuation, which effectively reduces the splicing loss with pure silica core few-mode transmission fiber. Low differential mode group delay is realized by using graded-index distribution. Also the effective index difference of the modes is greater than 0.5×10-3 to ensure low crosstalk between modes. The performance of the mode division multiplexer is investigated using the beam propagation method and full-vector finite element method. The result shows that the coupling efficiency of multiplexer is better than-0.479 dB, and the extinction ratio is higher than 31.2 dB in the wavelength of 1 400—1 700 nm. In C band, the average coupling efficiency of all mode channels of multiplexer is better than that of-0.140 dB, which shows flatness. The proposed scheme is an effective way to implement a multiplexer with low crosstalk, low los s, low fusion loss, high coupling efficiency, high extinction ratio and wide operating band.