Objective: The objective is to develop a high-power and high-efficient optical booster amplifier, compatible with WDM operation at 1064nm wavelength range. Two versions, with different output optical power and wall-plug efficiency requirements, are to be developed to address operation under space and ground environmental conditions. Targeted Improvements:Strategic component not available inESA's Member States nor in Cooperating/Associated States. Such component is key for the wavelength selection trade-off for future missions implementing optical inter-satellite links and optical space-ground links at data rates in excess of 100Gbps. Description: With the increasing data rate demands and longer distance communications, optical booster amplifiers (OBA) need to increase the output optical power while at the same time improving the overall electro-optical conversion efficiency. At 1064nm, space qualified OBA with TRL-9 provide 5Watts, while commercial available OBA for ground applications reach 100Watts. In both cases, operation is at single carrier amplification mode (e.g., no WDM operation), and wall-plug efficiency values up to 20% are reported for ground equipment. Future missions aim at establishing optical inter-satellite links and optical space-ground links at data rates in excess of 100Gbps (e.g., HydRON aims even at a Terabit-per-second optical transport network in the sky). To fulfil Terabit-per-second demands, therequired output optical power for the space and the ground OBA could reach up to 500W and 5kW respectively (depending on the transmitter aperture diameter and the effectiveness of the turbulence compensation countermeasures). These optical power levels are to beprovided either by a single OBA amplifying simultaneously all the optical WDM channels, or split among several OBA amplifying in parallel a reduced number of the optical WDM channels (which need then to be multiplexed at the output by means of a high-power optical multiplexer). This activity shall develop a space-based (single spatial mode) OBA with >100W output optical power, >30% wall-plug efficiency and >25 optical WDM channels, compatible with operation under space environmental conditions. In addition, this activity shalldevelop a ground-based (single spatial mode) OBA with >1kW output optical power, >20% wall-plug efficiency and >25 optical WDMchannels, which can operate in ground environmental conditions.