Bidirectional long-reach PON using Kramers-Kronig-based receiver for Rayleigh Backscattering noise and SSBI interference elimination.

Abstract

In this paper, a novel bidirectional long-reach PON is proposed and demonstrated by using Kramers-Kronig (KK)-based receiver and 7-core fiber to simultaneously cope with the induced signal-signal beating interference (SSBI) and Rayleigh backscattering (RB) noises. A low-cost self-homodyne detection using only one PD is used at both OLT and ONU, and the middle core of 7-core fiber is used to deliver the seed light to ONUs for colorless upstream transmission, and the upstream and downstream signals are transmitted simultaneously over the same outer core for each ONU. By this means, the signals and local oscillators for upstream and downstream transmission all originate from the same laser which is located at OLT. With the help of the KK-based receiver, SSBI could be effectively eliminated and the fiber dispersion can also be digitally compensated due to the reconstruction of the complex field of the received signal. Moreover, by using single sideband Nyquist-shaped subcarrier modulation with 16-ary quadrature amplitude modulation (SSB-Nyquist-16QAM) technique, the upstream and downstream signals are allocated to occupy the left and right sideband of the optical carrier respectively, and thus the RB noise can be easily removed by a simple optical filter in the receiver. In our experiment, the carrier-to-signal power ratio (CSPR) and the frequency gap between the upstream and downstream signals are investigated. Furthermore, bidirectional transmission of 60 Gbps SSB-Nyquist-16QAM signals over 50 km 7-core fiber are successfully achieved, and the frequency gap between the upstream and downstream signals is only 3 GHz.