iXblue with its partners Airbus D&S and CILAS recently built an engineering bread board (EBB) model of a laser communication system dedicated to high data rate transmission in space. The aimed application was focused on feeder links between low earth orbital (LEO) satellites and ground stations. The goal was to carry out a full evaluation of a WDM (Wavelength Division Multiplexing) communication system in the C-band infra-red window. The demonstration was based on four main building blocks: a transmitter Tx, a receiver Rx, a 5W high power optical amplifier (HPOA) and a digital processing unit (DPU). Data rates up to 25 Gb/s per channel were evaluated using two different modulation formats: OOK and DPSK.
iXblue oversaw the integration of the ModBox Tx module with its TRL-9 lithium niobate Mach-Zehnder modulators, its RF modulators drivers and related bias controllers. The ModBox Rx incorporated the iXblue low noise optical amplifier (LNOA) build with RadHard erbium doped optical fibers, the photoreceivers for the OOK detection and the differential photoreceivers connected to optical delay lines for the DPSK demodulation.
The bit error rate (BER) characterization was investigated with up to three WDM channels to determine the best trade-off in terms of power consumption, data rate and design complexity. The use of the HPOA was also investigated. Four Wave Mixing (FWM) was investigated. The full analysis of the characterization campaign allows us to determine the best configurations for multi Gb/s upstream and downstream optical communications in space.