Objective: The objective of the activity is to develop low noise and small footprint semiconductor laser diodes at 1064nm compatible with WDM operation and the associated low-power consumption driving electronics. The activity shall also investigate technologicaloptions to further reduce the footprint and the power consumption of the low-power section of an optical transmitter at 1064nm (e.g., integration of multiple lasers diodes, optical modulator, passive WDM components, etc. into the same package). Targeted Improvements: Enabling technology development for WDM operation at 1064nm (not existing today). Description: Wavelength Division Multiplexingis a technique commonly used in terrestrial high-capacity optical transport networks to increase the amount of traffic conveyed by one individual optical fibre. Laser sources with slightly different (but very stable) wavelengths, each of them carrying a certain amount of data, are multiplexed by means of passive photonic components into a single mode fibre. Because the lowest attenuation in standard single mode fibres used for terrestrial telecom applications is at the so-called third window (around 1550nm), manufacturershave focused the effort in developing laser sources fulfilling the standardized wavelength grid at 1550nm (according to the ITU recommendation "ITU G.694.1, Spectral grids for WDM applications: DWDM frequency grid"). For free space optical communications, 1064nmwasselected for EDRS because of the smaller diffraction (compared to 1550nm) and the availability of highly sensitive receivers basedon homodyne detection and BPSK modulation. The implementation of Laser Communication Terminal transmitting a single wavelength optical signal was sufficient to meet the data rates specified by the customers of the EDRS service. However, 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 evenat a Terabit-per-second optical transport network in the sky).To fulfil these demands, this activity shall develop WDM lasers sources around 1064nm (i.e., within the optical bandwidth of the optical booster amplifier at this waveband) with small footprint and low-power consumption driving electronics (similar to the WDM laser sources commercially available at 1550nm), while still fulfilling the phase noise specifications required by high sensitive receivers (e.g., based on homodyne detection or intradyne detection). In addition, techniques to further reduce the figure of merit of the overall optical transmitter at 1064nm in terms of footprint and power consumption shall be investigated and demonstrated (e.g., integration of multiple laser diodes into a single packaged component, or integrating other functionalities like optical modulation, passive multiplexing and medium-level optical amplification into the same component). As an outcome of the development, the activity shall elaborate on a proposal to standardize the wavelength grid at 1064nm, which potentially could be adopted by future missions like HydRON).