Study of all-optical mode regeneration based on few-mode Mach–Zehnder interferometer

Abstract

Mode division multiplexing (MDM) technology is a promising approach to improve the spectral efficiency of optical fibers. In MDM systems, all-optical mode regenerators can suppress the amplified spontaneous emission (ASE) noise and crosstalk of few-mode signals directly in the optical domain. In this paper, we focus on the mode regenerator based on few-mode Mach–Zehnder interferometer (FM-MZI) with a highly-nonlinear fiber, and propose an optimization method for the working points (WPs) of mode regeneration. An FM-MZI regenerator capable of supporting LP01, LP11, and LP21 modes is optimally designed for on/off keying (OOK) signals and the simulation results is in agreement with the theoretical analysis. Our simulation shows that, (1) when the input optical signal-to-noise ratios (OSNRs) of the three modes are 25 dB, 27 dB, and 27.5 dB, the FM-MZI regenerator has the maximum OSNR improvement by 1.7 dB, 1.5 dB, and 1.51 dB, respectively; (2) the introduction of the mode regenerator can reduce the bit error ratio (BER) of the 10 Gbit/s OOK system from 10−9 to 10−11, equivalent to the OSNR improvement by 1.87 dB, 2 dB, and 1.76 dB at BER = 10−9 for the three modes, respectively. In addition, we discuss the influence of optimization precision for the optical coupler, Q-factor improvement at different data rates, and Phase-preserving regeneration characteristics.