1 Tb/s - 4×343 Gb/s subcarriers on 50GHz grid - transmission over 480 km SMF with 22 GHz bandwidth semiconductor modulator

A 1 Tb/s option is demonstrated with 4 subcarriers on the 50 GHz grid, modulated with 43GBd PM-16QAM using a 40 Gb/s GaAs I/Q modulator module. 6dB of OSNR margins are obtained with transmission over 480km SMF.

1. Introduction

The future transmission bitrate hierarchy of 1 Tb/s will obviously be based on a superchannel or multiple subcarrier approach associated with advanced modulation formats [1], while the first generation of 400 Gb/s systems will be based on 2 subcarriers with dual-polarization (DP)-16QAM format and 32 Gbd symbolrate modulation. For 1 Tb/s systems various options have been proposed based on 2,3,4 [2], [3], [4] polarization multiplexed subcarriers, depending on the technically feasible symbolrates and the sizes M of the quadrature-amplitude modulation (M-QAM). LiNb0₃ (LN) I/Q modulators have been widely exploited in optical line cards due to their high speed operation and strong electro-optic effect. Photonic integrated circuits (PIC) based on 2-inch InP semiconductor technology have been realized for modulation of multiple subcarriers [5] as supporting smaller modules than possible with LN technology. Furthermore 6-inch GaAs technology appears very interesting, as a mature technology widely used for monolithic integration of microwave integrated circuits. A first on chip level GaAs I/Q modulator for QAM modulation at 25 Gbd has been demonstrated [6].