First experimental demonstration of a 3-dimensional simplex modulation format showing improved OSNR performance compared to DP-BPSK

We experimentally demonstrate a novel 3-dimensional modulation format with 1.2-dB OSNR tolerance improvement potential compared to DP-BPSK, as verified for the linear case. The non-linearity tolerance is evaluated in single-span transmission over 300km SSMF.

1. Introduction

Transmission over very long distances requires not only a low noise transmission line with only small distortions but also a modulation format, which exhibits a high tolerance to optical noise. Recently, 4-dimensional modulation formats have been proposed [1], in which both signal polarizations are co-modulated, resulting in an improved OSNR tolerance. In this paper, we report on a novel modulation format exhibiting the same spectral bandwidth as dual-polarization (DP-) BPSK, but with an improved OSNR tolerance. Signals with this modulation format are used to transmit over 300 km of standard-single mode fiber with an insertion loss of 63 dB, using only counter-directional Raman pumping and EDFA amplification.