Architecture for Reconfigurable Next-Generation Lasercom Terminals

Abstract

Optical intersatellite links (OISL), or laser communications (lasercom), offer 1 to 100+ Gbps data rates, with unequaled transmission security due to a laser beamwidth 100 to 1000 times narrower than an RF crosslink. As more high-value satellites are equipped with lasercom terminals, the space network lasercom architecture becomes more important. In this paper we propose a space lasercom crosslink architecture and wavelength-polarization plan for high-value satellites that enables lasercom terminal on-orbit reconfigurability for network robustness and flexible evolution. This lasercom reference architecture transmits and receives circularly polarized light, using three wavelengths separated by 5.6 nm on the ITU DWDM 50 GHz-grid. For resilient hardened networks, a different wavelength trio can be redefined before each link acquisition, anywhere in the 1538–1568 nm region suitable for the optical high power amplifier. We also present a reconfigurable optical bench design to realize maximum flexibility for intra or inter-network links, with resilience features for rapid crosslink establishment and robustness to hostile interference. Reconfigurable terminals also improve the network cost-effectiveness due to the connectivity flexibility. A brassboard reconfigurable optical bench reference design is being built at Aerospace Corp. The bench is $8.1^{\prime\prime} \mathrm{x} 8.4^{\prime\prime} \mathrm{x} 3.25^{\prime\prime}\mathrm{H}$, with an opto-mechanical design compatible for 2″ to 8″ telescopes, 10,000-84,000 km link ranges, and 1 to 100+ Gbps. The architecture is TRK-on-COM, with a rapid-acquisition capability using a star fix. The brassboard will demonstrate tunability across the 1550 nm C-band, for the TX laser pair and also for the RX and TX filters. We will demonstrate > 130 dB isolation of the 10W transmit power to the ACQ-TRK focal plane array 1 picowatt pixels. We intend to make the lasercom optical bench design details available as a reference design for adoption or adaptation, and to provide prototype performance test results on a non-proprietary, non-exclusive basis to encourage network adoption and interoperability and space qualification activities.