Noise and loss characteristics of microwave direct modulated optical links

Loss and noise figure of optical links transmitting microwave signals - e.g. for remote antennas in wireless communications - is dealt with. Conditions are rather general, including arbitrary matching conditions, shot noise and laser relative intensity noise. It is shown, that - alike passive microwave systems - noise figure is not proportional to the loss and theoretically it can be less than the loss. Optical power should be as low as possible - this limit being mainly determined by the required dynamic range of the system.