Assessment of the Performance of DPSK and OOK Modulations at 25 Gb/s for Satellite-Based Optical Communications

Airbus Defence and Space developed with its partners iXBlue and CILAS an engineering breadboard (EBB) model of optical communication chain able to manage nonreturn to zero (NRZ) on-off-keying (OOK) and differential phase shift keying (DPSK) modulations at 10 Gb/s and 25 Gb/s. The EBB includes a digital processing unit (DPU), an optical transceiver (Tx/Rx) and a 5 W-optical booster. It uses wavelength division multiplexing (WDM) technology to increase the total data rate. This is a first step towards the development of an engineering model (EM) that will be developed in 2020-2021. This paper reports a part of measurements performed on the EBB, particularly the performance of NRZ-OOK and NRZ-DPSK modulations for 3 × 25 Gb/s channels. Measurements reveal that non-linear effects start to appear inside the 5 W-booster. Because of its constant envelope during bit time, NRZ-DPSK signal is less sensitive to power modulation-related non-linear effects than NRZ-OOK The average sensitivity of the NRZ-OOK and NRZ-DPSK links at 25 Gb/s are respectively -36.8 dBm and -40.2 dBm for bit error ratio (BER) at 10
^-3
.