Deep Space Receiver Technology
The subject of the invention is a receiver for information transmitted using very weak light pulses, as well as a system and method for transmitting information using very weak light pulses. This invention offers a potential benefit when the value of the power spectral density is much less than the energy of one photon at the carrier frequency. This is now becoming increasingly relevant, as by 2025, the European Space Agency plans to be operating several missions that will place satellites in orbits around the Moon, the Earth-Sun Lagrange points, Mars and Jupiter. To manage this objective, initial studies are currently being performed to investigate optical communication systems that are likely to improve upon the present common radio frequency bandwidths by an order of magnitude. The target is to provide 100 Mbps channel bandwidth from 1 AU (the distance to the Sun) and with good global communication link coverage. The invention discloses two examples of scalable architectures for structured receivers: the first one, based on active polarization switching, maps Hadamard codewords composed from the binary phase shift keying (BPSK) constellation onto the standard pulse position modulation (PPM) format. The second receiver, using solely passive optical elements, converts phase-polarization patterns of coherent light pulses into a single pulse preserving a synchronized time of arrival. Such a conversion enables the implementation of a communication protocol equivalent to the PPM scheme, but with distributed optical power, provided that the intersymbol guard-time exceeds the pattern length.