Testing of a lightweight, small aperture ground terminal for LEO lasercom

We demonstrate a small aperture, lightweight, portable, and eye safe lasecom system that is capable of supporting ground to LEO lasercom links. The proposed system receives light directly into single mode fiber (SMF), without the need for adaptive optics (A0). Because it is SMF coupled it can support coherent detection modems, with bandwidth of up to 400 Gbps on a single wavelength. The system is fully capable of Terabit uplinks and downlinks, using commercially available technology. The system is a scaled-up version of our Point-to-Point lasercom system and has a bi-static configuration with separate 15cm transmit (Tx) and receive (Rx) apertures. The system is transportable and equipped with a mobilizer system that makes it simple to remove from its dedicated container and set up in a matter of minutes. Once set up, the system can be operated remotely through a web browser user interface. We present the results of characterization testing of the system. These tests include: fiber coupling efficiency and tracking performance, in both laboratory and field tests. We characterize the bias, jitter, and drift while tracking LEO satellites under both daytime and nighttime conditions. Because satellite terminals are not currently available in LEO orbit for direct testing of the system, we instead opt for testing the system in a Point-to-Point configuration using a surrogate space terminal. These outdoor point-to-point tests are carefully designed to reproduce the received power and scintillation index expected under actual operation. Passive tracking of satellites is performed under both daytime and nighttime conditions to verify pointing algorithms and receiver coupling efficiency. Our goal is to demonstrate that large aperture optics with complicated adaptive optics are not necessary for an Optical Ground Terminal (OGT) used with LEO satellite constellations.