FULL DUPLEX LASER COMMUNICATION TERMINAL ARCHITECTURE WITHOUT DEDICATED BEACON LASER

A laser communication architecture provides precise optical alignment between terminals without requiring dedicated beacon lasers or dedicated beacon wavelength optics. Instead, the same lasers and optics are used for both alignment and communication. A beacon modulation is applied to alignment beacons transmitted at or near communication wavelengths so as to differentiate them from communication beams. The beacon modulation can include phase and/or amplitude variation of a high frequency modulation, and/or "ping-pong" toggling of the beacon wavelength. In some full duplex red/blue embodiments, ping-pong modulation is implemented by alternated red/blue tuning of the transmit laser or by switching between separate red and blue transmit lasers, for example using a 2×1 laser switch, while maintaining constant beacon amplitude, thereby avoiding optical amplifier dynamic response issues. During communication, embodiments maintain optical alignment by diverting a percentage of received communication light to the tracking sensor.