Description: Free-space coherent optical communication systems require a single (spatial) mode to mode-match the optical local oscillator (laser) to the incoming optical communication signal. The use of low SWaP-C commercial terrestrial telecommunications fiber coupled transceivers (i.e., modems) is a great benefit. The single-mode-fiber coupled receiver core-diameter limits the fiber coupling (and thus overall) efficiency, Fast steering mirror (FSM) control systems are typically used to insure high coupling efficiency. The FSM systems require significant electrical power and cost. We propose to eliminate the FSM requirement using two innovations: a fly's-eye optics and an optical multimode to single-mode converter (a.k.a., photonic lantern). Further, the fly's-eye optics and photonic lantern could potentially reduce telescope optical requirements. In Phase 2, we designed, built and tested a full-duplex optical communication terminal with a 100 Gbps coherent transceiver and a phased array of 3 telescopes. Replacing the FSMs (3 units) with fly's eye receivers will result in lower weight on the gimbal. This reduces the gimbal motor load providing higher control loop bandwidth.

Benefits: Scalable versions of the innovations in the Optical Communication Array Transceiver (OCAT) will enable future data volume returns to and from NASA space missions in multiple domains with return data rates >100 Gbps (cislunar), >10 Gbps (Earth-Sun L1 and L2), >1 Gbps/AU2 (deep space), and >1 Gbps (planetary lander to orbiter and/or inter-spacecraft). The innovations in OCAT are for both spaceflight and ground systems and the array concepts can selectivity be applied to both coherent and direct detection systems.

Airbus, Eutelsat OneWeb, Laser Light Communications, and the US Space Development Agency (SDA) are pursuing MEO and GEO satellite constellations for global internet deployment. This is a key commercial market for scalable high-data-rate optical communication terminals. Total global mobile data traffic reached 93 EB/month in 2022 and is projected to grow 3.5 times to reach 329 EB/month in 2028.