A photonic crystal fiber broadband mode converter with highly fitting propagation constant

Abstract

Abstract In this paper, we propose a broadband mode converter based on photonic crystal fiber (PCF) starting from the method of propagation constant height fitting. Using the finite element method and the beam propagation method, three typical mode converters in the S + C + L range, LP01 to LP11, LP01 to LP21, and LP01 to LP31, are calculated. Numerical results show that the mode coupling efficiency of this mode converter is over 90% and the mode extinction ratio is over 10 dB. This converter can realize pattern multiplexing in a cascade manner. On this basis, we propose a multi-core mode multiplexer structure. On the premise of sacrificing some performance, three modes can be reused at the same time. Mode converters of PCF structure can be fabricated by PCF post-processing technology. It is expected to become an important part of the future mode division multiplexing (MDM) optical communication system.