Qualifying an integrated coherent receiver for space applications

Abstract

The development of space-based, free-space optical (FSO) communication systems is exciting for expanding internet connectivity worldwide. These systems will incorporate dense, low-earth constellations with short intersatellite links. Key to the performance of these satellite constellations are flexible architectures that support higher rates via complex modulation formats, with FSO data links varying between 10-100 Gb/s. However, prior efforts have designed custom modems optimized for each link, severely limiting their flexibility. An alternative is to leverage advances developed by the fiber telecom industry which offer high-rate high-sensitivity digital coherent communication systems while minimizing size, weight, and power (SWAP). These low-SWAP systems rely on commercially available microfabricated integrated coherent receivers (μICRs). Here we present data to help qualify a commercially available μICR for a space application; this data was collected through a series of environmental tests. This work thus expands the reach of coherent systems, allowing for the development of low-SWAP space-based FSO communication systems buttressed with commercially available μICRs. We achieved the space qualification of the μICR by monitoring the component’s bandwidth and electrooptical (EO) transfer function as environmental testing conditions were varied. We selected these environmental conditions to simulate a low-Earth orbit. The environmental testing included: (i) irradiation using a cobalt-60 source up to a total ionizing dose of 100 kilorads, extending qualification to all of the commercial orbits; (ii) thermal cycling with survival temperatures ranging from -40 °C to 70 °C and operational temperatures varying between -5 °C and 65 °C with the part cycled between its survival temperature range twice and its operational range an additional ten times over a 7-day period; (iii) vibration testing to 28 GRMS for 180 seconds on each axis; (iv) shock to a maximum of 1201 g; and (v) thermal vacuum testing at ∼ 6.3 × 10⁻⁶ torr. We observed no degradation in device EO performance after environmental testing.