The performance analysis of optical spaceborne communication systems shows that the main advantages of Nd:host-laser based IOL/ISL's resides in the high, scalable output power combined with a very narrow laser linewidth, which permits the implementation of very sensitive, coherent optical receivers. As laser output power will increase, the overall transmitter-laser and modulator-efficiency will gain importance and could finally decide the competitivity of the Nd:host laser technology. An overall laser reliability higher than that of the individual pumping diodes, as well as low transmitter mass and volume are additional important aspects. Preliminary experiments performed to assess the feasibility of both heterodyne and homodyne optical receivers were successfully carried out. A heterodyne optical receiver achieved shot noise limited operation and approached - after the IF-stage - the theoretical limit to AAdthin 4 dB to 5 dB. A simple optical PLL was also demonstrated. The residual phase errors were as low as 15° peak-to-peak with a filter loop bandwidth of 20 kHz. These laboratory results are part of a program which finally should lead to a representative and cost-efficient far field demonstration experiment for free-space Nd:Host laser communication systems.