Proceedings Article | 11 June 2021
High capacity throughputs are more and more requested by satellite owners, even before launching the first generation of optical constellations. MPB is developing a commercially-competitive photonics subsystem that increases the data throughput of a “free-space” optical link in a space environment. The objective is to build and demonstrate an optical subsystem suitable for deployment in space with a target capacity of ≥100Gbit/s having a scalable architecture optimized for cost per Gbit, while maintaining acceptable (e.g. 10-4) pre-FEC bit error ratio (BER), high reliability, design flexibility. The two most promising solutions for the 100Gbps links use either a suitably-adapted commercial 100 Gbps x 1ch transceiver (e.g. commercial Dual-Pol 28Gbaud, 4 bits/symbol) or wavelength-agile WDM 10 Gbps x 10ch, or similar system (e.g. 12.5 Gbps x 8ch). The subsystem is based on the selected optimal architecture, convenient for space environment, and potentially comprising one or more of the “throughput-enhancing” possible approaches; such as the Modulation bitrate, Wavelength multiplexing (WDM), and Spectral efficiency. A large number of the performance parameters are also involved in the evaluation of the optimal solution, including: OSNR, Power at Rx, Mass and Volume, Cost, Complexity of the Software and Hardware to develop, Reliability/Redundancy, Power-Consumption and wall-plug Efficiency (W/Gbps), Signal Modulation, BER, and Stimulated Brillouin Scattering. MPB plans to verify that the 100G commercial transceiver, a coherent module optimized for terrestrial use, is compatible with the harsh space environment. Moreover, its design needs to be modified (in collaboration with the manufacturer) in order to employ distinct Tx and Rx wavelengths. Although such an approach enables all data to be sent over a single wavelength, in the event of an e.g. Tx optical-amplifier failure all transmission capability would be lost. The coherent transceivers themselves are very complicated in design, but this development has already been carried out by the manufacturer for terrestrial applications. The WDM option 10 G x 10ch has a larger mass, volume, and power per Gbps, however, the technology is based on MPB-developed boosters for space applications and offers higher redundancy (i.e. if one optical Tx amp fails, the other nine channels can still transmit). This option adds more complexity and cost since it needs to develop more software and hardware items. This development is useful for the other amplifiers with similar requirements from space primes. In addition, we are including a detailed study and prototyping of a space-borne Reconfigurable Optical Add-Drop Multiplexer (ROADM), which would enable greatly enhanced dynamic bandwidth allocation. The two approaches (single-channel high BW vs multi-channel medium BW) have respective advantages and disadvantages.
